ADVANTAGE SPOTLIGHT ON ANSYS 12.0

ADVANTAGE SPOTLIGHT ON ANSYS 12.0
ADVANTAGE
TM
EXCELLENCE IN ENGINEERING SIMULATION
VOLUME III
ISSUE 1
2009
SPOTLIGHT ON
ANSYS 12.0
FRAMEWORK
MULTIPHYSICS
PAGE 6
PAGE 11
HIGH-PERFORMANCE
COMPUTING
PAGE 25
© iStockphoto.com/Atrapat
EDITORIAL
Engineering
Simulation:
Needed Now
More Than Ever
In a tough economy, forward-thinking companies
are investing in leading-edge simulation
technology to drive top-line revenue growth
and bottom-line savings.
Time and cost benefits of engineering simulation are
well documented. Predicting product performance and
determining optimal solutions early in the design phase help
to avoid late-stage problems and to eliminate trial-and-error
testing cycles that drive up costs and bog down schedules.
Simulation enables engineers to perform what-if studies
and to compare alternatives, processes that otherwise
would be impractical. Indeed, bottom-line savings are
one key benefit that prompts most companies to implement
simulation, and are most readily quantified in return-oninvestment calculations.
A second, and potentially greater, benefit is boosting
top-line revenue growth. With simulation, companies can
develop innovative, winning products that stand apart from
others, make the status quo obsolete or create entirely new
market opportunities. Brand value can be enhanced
by tuning product performance to specific performance
characteristics. Revenue streams may be expanded by
increasing design throughput of new products or tackling
projects that otherwise would not be attempted.
How specific companies leverage simulation in
achieving these benefits depends on their unique products,
engineering challenges and business requirements. The
possibilities are limitless. Case in point is detailed in this
issue’s article “Predicting 3-D Fatigue Cracks without a
Crystal Ball” from Honeywell Turbo Technologies. Engineers
used software from ANSYS to predict thermomechanical
fatigue cracks in turbochargers for internal combustion
engines. Predicting crack failures early enables engineers to
optimize designs upfront and helps to avoid qualification
test failures that lead to additional rounds of tests — which
can be very expensive and take weeks to complete. Further,
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this simulation method has the potential to reduce crack
growth analysis time by over 90 percent compared
with manual methods. The productivity gain will enable
engineers to analyze more designs annually, thus keeping
up with increased demand for turbochargers around the
world and strengthening the company’s leadership
position in this competitive industry sector.
The prediction method is based on improved fracture
mechanics capabilities for calculating J integrals, one of
the many enhancements in ANSYS 12.0. Previewed in the
Spotlight section of this issue, the release is a milestone
for the software supplier and a huge step forward for the
CAE industry in terms of advancements in individual
physics (structural, fluid, thermal and electromagnetics)
and integration of this functionality into a unified multiphysics framework for Simulation Driven Product
Development — an approach leading to top-line revenue
growth and bottom-line savings for many companies.
Discussion of the business value of simulation is
particularly relevant in today’s world as manufacturers
face the toughest economic climate of a lifetime. Indeed,
with their survival at stake, forward-thinking companies
recognize the need to invest in engineering simulation now
more than ever to withstand the current market turbulence
and to strengthen their long-term competitive position,
brand value and profitability as conditions improve in the
coming years. ■
John Krouse, Senior Editor and Industry Analyst
ANSYS Advantage • Volume III, Issue 1, 2009
1
CONTENTS
Table of Contents
SPOTLIGHT ON ANSYS 12.0
4 ANSYS 12.0
Launching a New Era of
Smart Engineering Simulation
A full generation ahead of other solutions, ANSYS 12.0 takes
product design and development to the next level.
6 FRAMEWORK
4
Introducing ANSYS Workbench 2.0
Proven simulation technology is delivered in a truly
innovative integration framework.
8 GEOMETRY AND MESHING
Taking Shape in 12.0
ANSYS combines depth of simulation with industry experience to provide
geometry and meshing tools that realize simulation results faster.
11 MULTIPHYSICS
Multiphysics for the Real World
8
In ANSYS 12.0, multiphysics capabilities continue to increase in flexibility,
application and ease of use.
14 ELECTROMAGNETICS
ANSYS Emag 12.0 Generates Solutions
Improved accuracy, speed and platform integration advance the capabilities
of low-frequency electromagnetic simulation.
15 FLUIDS
A Flood of Fluids Developments
A new integrated environment and technology enhancements
make fluids simulation faster, more intuitive and more accurate.
11
18 STRUCTURAL MECHANICS
Designing with Structure
Advancements in structural mechanics allow more efficient and
higher-fidelity modeling of complex structural phenomena.
22 EXPLICIT DYNAMICS
Explicit Dynamics Goes Mainstream
ANSYS 12.0 brings native explicit dynamics to ANSYS Workbench and
provides the easiest explicit software for nonlinear dynamics.
23 EIGENSOLVER
Introducing the Supernode Eigensolver
15
A new eigensolver in ANSYS 12.0 determines large numbers
of natural frequency modes more quickly and efficiently than
conventional methods.
25 HIGH-PERFORMANCE COMPUTING
The Need for Speed
From desktop to supercomputer, high-performance computing with
ANSYS 12.0 continues to race ahead.
28 FUTURE DIRECTIONS
Foundations for the Future
The many advanced features of ANSYS 12.0 were designed to solve today’s
challenging engineering problems and to deliver a platform for tomorrow’s
simulation technology.
22
2
ANSYS Advantage • Volume III, Issue 1, 2009
www.ansys.com
CONTENTS
DEPARTMENTS
SIMULATION @ WORK
31 AUTOMOTIVE
47 TIPS AND TRICKS
Predicting 3-D Fatigue Cracks without
a Crystal Ball
ANSYS tools quickly predict 3-D thermomechanical fatigue
cracking in turbocharger components.
33 HEALTHCARE
Reusing Legacy Meshes
ANSYS tools enable users to work with finite element models
in various formats for performing simulations as well as
making changes to part geometry.
49 ACADEMIC
Electromagnetics in Medicine
Electromagnetic and thermal simulations find use in medical
applications.
Expanding Stent Knowledge
Simulation provides the medical industry with a closer look
at stent procedures.
36 ELECTRONICS
Keeping Cool in the Field
A communications systems company gains millions of dollars by
using thermal simulation to bring tactical radios to market faster.
38 BUILT ENVIRONMENT
Designing Against the Wind
Simulation helps develop screen enclosures that can better
withstand hurricane-force winds.
40 ENVIRONMENT
Stabilizing Nuclear Waste
Fluid simulation solidifies its role in the radioactive waste
treatment process.
38
42 OPTIMIZATION
Topology Optimization and Casting:
A Perfect Combination
Using topology optimization and structural simulation helps
a casting company develop better products faster.
44 MARINE
Fighting Fire with Simulation
The U.K. Ministry of Defence uses engineering simulation
to find alternatives to ozone-depleting substances for
fire suppression.
49
For ANSYS, Inc. sales information, call 1.866.267.9724, or visit www.ansys.com.
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Executive Editor
Fran Hensler
Managing Editor
Chris Reeves
Senior Editor and
Industry Analyst
John Krouse
Editors
Erik Ferguson
Shane Moeykens
Mark Ravenstahl
Contributors
Susan Wheeler
Marty Mundy
Ad Sales Manager
Helen Renshaw
Editorial Advisor
Kelly Wall
Circulation Manager
Sharon Everts
About the Cover
ANSYS introduces release 12.0,
the next-generation technology
for Simulation Driven Product
Development. The spotlight
begins on page 4.
Designer
Miller Creative Group
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ANSYS Advantage • Volume III, Issue 1, 2009
3
© 2009 ANSYS, Inc. All rights reserved.
ANSYS 12.0:
Launching a New Era of
Smart Engineering Simulation
A full generation ahead of other solutions, ANSYS 12.0 takes product
design and development to the next level.
By Jim Cashman, President and CEO, ANSYS, Inc.
The current economic climate has completely changed
the way most companies view engineering simulation.
Leveraging the power of virtual prototyping to compress the
product development process and drive down costs is no
longer a choice — it’s a requirement for survival in an
increasingly competitive environment.
In nearly every industry, driving product development
through engineering simulation technology has become a
key strategy to develop more innovative products, reduce
development and manufacturing costs, and accelerate time
to market.
Backed by the unmatched power of ANSYS 12.0
software, progressive companies are taking engineering
simulation a step beyond. They have already realized
the enormous strategic benefits of virtual prototyping — and
are now seeking more from their investments in simulation.
ANSYS 12.0 enables these forward-looking companies
to maximize the efficiency of their simulation processes, to
increase the accuracy of their virtual prototypes, and to
capture and reuse their simulation processes and data. This
next level of performance signals a new era of Smart
Engineering Simulation, in which product innovations can be
realized more rapidly, and more cost effectively, than
ever before.
There is no company better qualified to launch this new
era. ANSYS has led the engineering simulation industry
for nearly 40 years, revolutionizing the field of engineering
simulation in much the same way that the internet and desktop
publishing have revolutionized the broadband distribution
of information. As a direct consequence of a long-standing
commitment to simulation, ANSYS is the only company
offering advanced simulation technologies that span all key
engineering disciplines — and bringing them together in an
integrated and flexible software platform designed specifically
to support Simulation Driven Product Development.
Over the years ANSYS has made significant technology
investments, acquisitions and partnership to ensure continuing
leadership. We recognize that every technology breakthrough
or market accomplishment has only been a stepping stone to
our vision. Reflecting these investments — as well as the
acquired wisdom of four decades in this industry — ANSYS
12.0 represents the fullest expression of our leadership position. It is the most comprehensive engineering simulation
solution available today.
While the following pages offer a wealth of detail, I’d like to
focus on the high-level benefits that our customers will realize
as they leverage the full depth and breadth of ANSYS 12.0 to
make product development smarter, better, faster and more
collaborative than they ever thought possible.
Smart Technologies = Smart Simulation
At ANSYS, we have applied our long history of technology leadership to create the world’s smartest solution for
engineering simulation — more automated, repeatable,
Some images courtesy FluidDA nv, Forschungszentrum Jülich GmbH,
Heat Transfer Research, Inc., Riello SPA and © iStockphoto.com/iLexx.
4
ANSYS Advantage • Volume III, Issue 1, 2009
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persistent and intuitive than existing products. The groundbreaking ANSYS Workbench 2.0 platform is a flexible
environment that allows engineers to easily set up, visualize
and manage their simulations. ANSYS 12.0 offers
unequalled technical breadth that allows customers to
explore a complete range of dynamic behavior, from
frequency response to large overall motion of nonlinear
flexible multibody systems. ANSYS has also leveraged
its industry-leading capabilities to create an unequalled
depth of simulation physics, including the newly integrated
ANSYS FLUENT solver, advancements in all key simulation
physics, and enabling technologies for meshing, geometry
and design optimization. ANSYS Engineering Knowledge
Manager allows engineers to easily archive, search, retrieve
and report their simulation data via a local machine or a
centralized data repository. Not only does ANSYS 12.0
represent the smartest and best individual technologies, but
it brings them together in a customized, scalable solution
that meets the highly specific needs of every engineering
team. Powerful and flexible, ANSYS 12.0 can be configured
for advanced or professional users, deployed to a single user
or enterprise, and executed on laptops or massively parallel
computer clusters. As customer requirements grow and
mature, ANSYS 12.0 is engineered to scale up accordingly.
Better Prototypes, Better Products
With its unique multiphysics, high-performance
computing and complete system modeling capabilities,
ANSYS 12.0 is a complete solution that takes virtual prototyping to a new level of accuracy, realism and efficiency.
ANSYS 12.0 captures the response of a completely
assembled system and assesses how a range of highly
complex, real-world physical phenomena will affect not only
individual components but also their interactions with one
another. Flaws in product functionality can be recognized
before investments are made in full-blown physical prototypes — and ideas that are validated in the virtual world can
be fast-tracked to maximize agility and capture emerging
market opportunities. Powered by fast and accurate solvers,
design optimization with ANSYS 12.0 results in prototypes
with a much higher probability of ultimate market success.
Product Design at Warp Speed
ANSYS 12.0 automates many manual and tedious tasks
involved in simulation, reducing design and analysis cycles
by days or even weeks. An innovative project management
system allows custom simulation workflows to be created,
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captured and automated with drag-and-drop ease. ANSYS
12.0 amplifies the capabilities and outputs of every member
of the engineering staff, enabling them to work smarter,
to intelligently make design trade-offs and to rapidly
converge on the best designs. And, because ANSYS 12.0 is
based on the most advanced technology and physics,
design and engineering teams can commit to manufacturing
operations with confidence — and without investing time
and money in exhaustive physical testing.
Redefining Collaboration
Real-world simulation projects often involve a wide
variety of engineering personnel — and generate large
volumes of data that must be shared across the enterprise.
With its broad support of simulation disciplines and native
project management system, ANSYS 12.0 allows
engineering teams to collaborate more freely, without
software barriers or other technology obstacles. Within a
single project, several engineers can assess their designs
within individual disciplines, as well as easily coordinate
multiphysics simulations. The single-project environment reduces redundancies and synchronization errors
among different engineering teams. ANSYS Engineering
Knowledge Manager also provides the tools to manage
the workflow of a group of engineers and a myriad of
simulation projects.
At ANSYS, we have always believed that engineering
simulation is a sound investment — and today, it is emerging
as one of the smartest investments an organization can
make. We understand the incredible time and cost pressures
under which our customers operate today, and ANSYS 12.0
is specifically designed to help them meet these challenges.
In the new era of Smart Engineering Simulation heralded
by ANSYS 12.0, product development teams can work
faster and more effectively than ever before — with a greater
degree of confidence in their finished products. Because it
provides a tremendous opportunity for engineers to design
higher-quality, more innovative products that are manufactured faster, and at a lower cost, ANSYS 12.0 makes the
most compelling case yet for engineering simulation as a
powerful competitive strategy. But we are far from finished:
ANSYS 12.0 is a milestone, not the destination, as we
continually work to put our tools in the hands of every
engineer who can benefit from them. As the power of
ANSYS 12.0 is unleashed by imaginative engineering teams
around the world, I look forward to the amazing product
innovations that will result. ■
ANSYS Advantage • Volume III, Issue 1, 2009
5
12.0: FRAMEWORK
Introducing
ANSYS Workbench 2.0
Proven simulation technology is delivered in a truly
innovative integration framework.
ANSYS 12.0 delivers innovative,
dramatic simulation technology
advances in every major physics
discipline, along with improvements in
computing speed and enhancements
to enabling technologies such as
geometry handling, meshing and
post-processing. These advancements
alone represent a major step ahead
on the path forward in Simulation
Driven Product Development. But
ANSYS has reached even further by
delivering all this technology in an
innovative simulation framework,
ANSYS Workbench 2.0.
The ANSYS Workbench environment is the glue that binds the
simulation process; this has not
changed with version 2.0. In the original
ANSYS Workbench, the user interacted
with the analysis as a whole using the
platform’s project page: launching the
various applications and tracking the
resulting files employed in the process
of creating an analysis. Tight integration
between the component applications
yielded unprecedented ease of use for
setup and solution of even complex
multiphysics simulations.
In ANSYS 12.0, while the core
applications may seem familiar, they
are bound together via the innovative
project page that introduces the
concept of the project schematic.
This expands on the project page
concept. Rather than offer a simple
list of files, the project schematic
presents a comprehensive view of
the entire analysis project in flowchart form in which explicit data
relationships are readily apparent.
Building and interacting with these
flowcharts is straightforward. A toolbox
contains a selection of systems that
form the building blocks of the project.
To perform a typical simulation, such
6
The toolbox, at left, contains systems that form a project’s building blocks. In this single-physics example, the user drags
the system (from left) into the project schematic (at right), then sets up and solves the system, working from the top
down through the cells in the system. As shown, the Fluid Flow system (at right) is complete through mesh generation,
as shown by green check marks.
as static structural analysis, the user
locates the appropriate analysis
system in the toolbox and, using dragand-drop, introduces it into the project
schematic. That individual system consists of multiple cells, each of which
represents a particular phase or step
in the analysis. Working through the
system from the top down, the user
completes the analysis, starting with a
parametric connection to the original
CAD geometry and continuing through
to post-processing of the analysis
result. As each step is completed,
progress is shown clearly at the project
level. (A green check mark in a cell indicates that an analysis step has been
completed.)
Passing files and data from one
application to the next is managed
entirely by the framework, and data
and state dependencies are directly
represented. More-complex analyses
can be constructed by joining multiple
systems. The user simply drags a new
system from the toolbox and drops
it onto the existing system in the
ANSYS Advantage • Volume III, Issue 1, 2009
schematic. Connections are created
automatically and data is transferred
behind the scenes, delivering drag-anddrop multiphysics with unprecedented
ease of use.
The ANSYS Workbench environment tracks dependencies among the
various types of data in the project. If
something changes in an upstream
cell, the project schematic shows that
downstream cells need to be updated
to reflect these changes. A projectlevel update mechanism allows these
changes to be propagated through all
dependent cells and downstream
systems in batch mode, dramatically
reducing the effort required to repeat
variations on a previously completed
analysis.
Parameters are managed at the
project level, where it is possible to
change CAD and geometry parameters,
material properties and boundary
condition values. Multiple parametric
cases can be defined in advance
and managed as a set of design
points, summarized in tabular form
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12.0: FRAMEWORK
on the ANSYS Workbench project page.
Design Exploration systems can be
Managing Simulation Data
connected to these same project-level
With the ever-increasing use of simulation, keeping track of the
parameters to drive automated design
expanding volume of simulation data becomes more and more difficult.
investigations, such as Design of ExperiThe need to be able to quickly locate information for reuse is paramount to
ments, goal-driven optimization or Design
increasing productivity and reducing development costs.
for Six Sigma.
ANSYS EKM Desktop is a new tool, integrated in the ANSYS
In addition to serving as a framework
Workbench environment, that facilitates managing simulation data from
for the integration of existing applications,
multiple projects. ANSYS EKM Desktop is a single-user configuration
the ANSYS Workbench 2.0 platform also
of EKM that allows users to add files from any project to a local virtual
serves as an application development
repository. Simulation properties and other metadata are automatically
framework and will ultimately provide
extracted (or created) from files when added, and users can tag files with
project-wide scripting, reporting, a user
unique identifiers at any time. These attributes can all be used to search
interface (UI) toolkit and standard data
and retrieve files based on keywords or complex search criteria. Reports
interfaces. These capabilities will emerge
can be easily generated to allow efficient side-by-side comparison of the
over this and subsequent releases. At
attributes of related analyses. Search queries and reports can be saved for
ANSYS 12.0, Engineering Data and
later re-use. Files that are retrieved can be directly launched in their associANSYS DesignXplorer are no longer
ated simulation application from within the ANSYS EKM Desktop tool.
independent applications: They have been
re-engineered using the UI toolkit and
integrated within the ANSYS Workbench
project window.
Beyond managing individual simulation projects, ANSYS Workbench
interfaces with the ANSYS Engineering
Knowledge Manager (EKM) product
for simulation process and data
management. At ANSYS 12.0, ANSYS
Workbench includes the single-user
configuration of ANSYS EKM, called
ANSYS EKM Desktop. (See sidebar.)
ANSYS Workbench 2.0 represents a
sizable step forward in engineering simulation. Within this innovative software
framework, analysts can leverage a
complete range of proven simulation
technology, including common tools for More-complex analyses involving multiple physics can be built up by connecting systems. Data dependencies are
CAD integration, geometry repair and indicated clearly as connections. State icons at the right of each cell indicate whether cells are up to date, require user
meshing. A novel project schematic input or need to be updated — for example, whether they are just meshed or fully solved.
concept guides users through complex
analyses, illustrating explicit data
relationships and capturing the process
for automating subsequent analyses.
Meanwhile, its parametric and persistent
modeling environment in conjunction
with integral tools for design optimization
and statistical studies enable engineers
to arrive at the best design faster.
Looking beyond ANSYS 12.0, the
ANSYS Workbench platform will be
further refined: The aim is to deliver a
comprehensive set of simulation technology in an open, adaptive software
architecture that allows for pervasive
customization and the integration of
third-party applications. ■
Judd Kaiser, Shantanu Bhide, Scott Gilmore and Todd
McDevitt of ANSYS, Inc. contributed to this article.
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Two analyses from the schematics shown in the previous figure are shown here in the mechanical simulation application.
Launched from the schematic, individual applications may be familiar to existing users.
ANSYS Advantage • Volume III, Issue 1, 2009
7
12.0: GEOMETRY AND MESHING
Taking Shape
in 12.0
ANSYS combines depth of simulation
with industry experience to provide
geometry and meshing tools that realize
simulation results faster.
Engineering simulation software
users have been known to spend up to
90 percent of their simulation-related
time working on pre-processing tasks.
By targeting developments in capabilities
to increase ease of use, simplifying
pre-processing tasks, and increasing the
capabilities of pre-processing tools,
ANSYS has systematically delivered
exciting advances to increase the
efficiency of simulation.
ANSYS has combined rich
geometry and meshing techniques
with its depth of knowledge and
experience, and the end result is
products capable of harnessing
integrated geometry and meshing
solutions that share core libraries
with other applications. At releases
10.0 and 11.0, ANSYS introduced
robust, new meshing capabilities
from ANSYS ICEM CFD and ANSYS
CFX tools into the ANSYS meshing
platform — which provides the foundation
for unifying and leveraging meshing technologies, making them interoperable and
available in multiple applications. Taking
advantage of the enhanced ANSYS
Workbench 2.0 framework, the company
provides further significant improvements for ANSYS 12.0 geometry and
meshing applications.
CAD Connections
ANSYS continues to deliver a leading
CAD-neutral CAE integration environment, providing direct, associative and
bi-directional interfaces with all major
CAD systems, including Unigraphics®,
Autodesk ® Inventor ®, Pro/ENGINEER®,
CATIA® V5, PTC CoCreate® Modeling,
SolidEdge®, SolidWorks®, and Autodesk®
Mechanical Desktop®. Software from
ANSYS also supports file-based readers
Automated cleanup and repair of imported geometry:
New tools automatically detect and fix typical problems,
such as small edges, sliver faces, holes, seams and faces
with sharp angles. Geometry models can now be prepared
for analysis at a much faster pace. These images show an
aircraft model before (top) and after (bottom) cleanup.
for IGES, STEP, ACIS®, Parasolid®,
CATIA® V4 and CATIA V5. At ANSYS
12.0, geometry interfaces have been
enhanced to import more information
from CAD systems, including new data
types such as line bodies for modeling
beams, additional attributes such as
colors and coordinate systems, and
improved support for named selections
created within the CAD systems.
For pre-processing larger models,
release 12.0 includes support for 64-bit
operating systems, and smart and
selective updates of CAD parts. The
newly introduced ability to selectively
update CAD components allows users
to update individual parts instead of an
entire assembly, thus making geometry
updates much faster and more targeted.
“ANSYS 12.0 will set the stage
for major
improvements in our design processes. Two of Cummins’
core tools, ANSYS FLUENT and ANSYS Mechanical, are
coming together in the ANSYS Workbench environment. I
am also very pleased to see that geometry import continues
to improve, and we have several more meshing options.”
— Bob Tickel
Director of Structural and Dynamic Analysis
Cummins, Inc.
8
ANSYS Advantage • Volume III, Issue 1, 2009
Improved surface extension: Users can select and extend
multiple groups of surfaces in a single step, a procedure
that greatly simplifies the process of closing gaps between
parts after mid-surface extraction. The images show a
sample model before and after surface extension.
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12.0: GEOMETRY AND MESHING
Geometry Handling in
ANSYS DesignModeler
Geometry modeling in the ANSYS
Workbench environment is greatly
improved to provide increased
automation, greater flexibility and
improved ease of use for the task of
preparing geometry for analysis. The
feature-based, parametric ANSYS
DesignModeler tool, which can be used
to create parametric geometry from
scratch or to prepare an existing CAD
geometry for analysis, now includes
automated options for simplification,
cleanup, repair and defeaturing.
Merge, Connect and Project
features have been added for improved
surface modeling in ANSYS 12.0. Face
and Edge merge operations can be
used to easily simplify models by
eliminating unnecessary features and
boundaries, leading to improved mesh
and solution quality. The Connect
operation can be applied to ensure
proper connectivity in models with gaps
and overlaps.
Automated cleanup and repair
capabilities have been improved in the
12.0 release. New tools automatically
detect and fix typical problems, such as
small edges, sliver faces, holes, seams
and faces with sharp angles. Geometry
models can now be prepared for analysis at a much faster pace. As always,
analysis settings remain persistent after
performing these operations and are
updated automatically in response to
changes in geometry.
Shell modeling has been enhanced
in several ways, including improved
surface extensions. The ability to select
and extend groups of surfaces greatly
simplifies the process of closing gaps
between parts after mid-surface extraction. The result is easier modeling of
welds, for example.
Analysis-specific tools within the
ANSYS DesignModeler product now
include an automated option to extract
flow volumes for fluid dynamics analyses. In addition, several new features,
including user-defined offsets, userdefined cross sections and better
orientation controls, are available for
improved beam modeling for structural
analyses.
www.ansys.com
Improved attribute support is
available with ANSYS DesignModeler
12.0. This includes options to create
attributes within ANSYS DesignModeler
as well as to import additional attributes
from external CAD, including named
selections, coordinate systems and
work points.
ANSYS Meshing Platform
A primary focus for ANSYS 12.0 has
been to provide an automated meshing
solution that is best in class for fluid
dynamics. With the addition of capabilities from GAMBIT and TGrid
meshing applications, major improvements have been made in the automatic
generation of CFD-appropriate tetrahedral meshes with minimal user input.
Advanced size functions (similar to those
found in GAMBIT), prism/tet meshing
(from TGrid) and other ANSYS meshing
technologies combine to provide
improved smoothness, quality, speed,
curvature and proximity feature
capturing, and boundary layer capturing.
In the area of hex meshing, the traditional sweep and thin sweep methods
have seen evolutionary improvements.
A new method called MultiZone has
been integrated into the ANSYS
meshing platform. By combining
existing ANSYS ICEM CFD Hexa
technology with improvements in
automation, MultiZone allows the user
to automatically create hex meshes for
many complex geometries without
requiring geometry decomposition.
Thin solid sweep method: Using the thin solid sweep mesh
method, complicated sheet metal parts can be easily hex
meshed without the need for midsurfacing or welding. The
mesh can be generated to conform to the shared interface
to increase the accuracy and speed of the solution.
Patch conformal tet method with advanced size functions:
With minimal input, ANSYS size function–based triangulation
and inflation technology can handle advanced CFD meshing
challenges, such as this benchmark aircraft model.
In the area of hybrid meshing, the
MultiZone method allows for complicated regions to be meshed with a
hybrid mesh (tet, hex-core, hex-dominant), further improving the flexibility and
automation of this meshing approach.
For more control in key areas of concern,
the Sweep and Patch Conforming
methods can be employed with
conformal inflation layers throughout.
Though many of these enhancements were driven by fluid dynamics
needs, they also benefit users of other
types of simulation. For example, users
performing structural analyses will benefit
from the improved automation and mesh
quality. Additional meshing enhancements for structural analyses include:
• Physics-based meshing
improvements
• Rigid body meshing for contact
• Automated meshing of gaskets
• Improved handling of beams
MultiZone mesh method: Using the new MultiZone mesh
method, a user can mesh complicated models with a pure
hex mesh without the need for geometry decomposition.
This brake rotor example can be meshed with a pure hex
mesh in a single operation.
• Thin solid meshing improvements
• Support for multiple elements
through the thickness
ANSYS Advantage • Volume III, Issue 1, 2009
9
12.0: GEOMETRY AND MESHING
Hybrid mesh: Using a combination of sweep and tetrahedral mesh methods, a user can quickly control the mesh
in regions of interest to improve the accuracy of the
solution without the need for a pure hex mesh (and the
time required to generate it).
• Generation of conformal meshes
in multi-body parts
• Enhanced and new mesh
controls
• Pinch features to help in
defeaturing models
• Improved smoothing
• Improved flexibility in size
controls and mesh refinement
• Arbitrary mesh matching to
improve node linking and
solver accuracy
These improvements, though driven
by structural analysis needs, provide
benefits to the entire spectrum of
ANSYS users.
ANSYS ICEM CFD
For ANSYS 12.0, ANSYS ICEM CFD
meshing development focused on two
primary tasks: improved implementation of ANSYS ICEM CFD meshing
Named selection manager: This new feature allows a user
to create and save named selections within CAD systems
and then to use them within ANSYS applications. This
example uses the named selection manager within
Pro/ENGINEER.
10
technology within the ANSYS meshing
platform and continued development to
enhance the ANSYS ICEM CFD product
for interactive meshing customers.
Because the ANSYS ICEM CFD integration involves the sharing of core
libraries, improvements made for the
ANSYS meshing platform also enhance
the ANSYS ICEM CFD meshing product
(and vice versa).
MultiZone meshing is an example
of a crossover technology that has
received special attention in both
ANSYS meshing and the stand-alone
ANSYS ICEM CFD meshing product.
This hybrid meshing method combines
the strengths of various meshers, such
as ANSYS ICEM CFD Hexa and TGrid,
in a semi-automatic blocking framework. Within the ANSYS Workbench
environment, multizone automation
provides multi-source, multi-target
and multi-direction sweep capabilities
reminiscent of the GAMBIT Cooper tool.
In the stand-alone ANSYS ICEM CFD
product, this is an excellent way to
mesh for external aerodynamics in a
semi-automated way that provides
rapid hybrid meshing with a high degree
of control and quality.
Improvements for ANSYS ICEM
CFD 12.0 include process and interface
streamlining, new hexa features, BFCart
mesher enhancements, mesh editing
advancements, output format updates
and more. ■
Ben Klinkhammer, Shyam Kishor, Erling Eklund,
Simon Pereira and Scott Gilmore of ANSYS, Inc.
contributed to this article.
ANSYS ICEM CFD: MultiZone meshing that combines
the strength of various meshing tools, automatically
generated this hybrid grid for a tidal turbine.
ANSYS Advantage • Volume III, Issue 1, 2009
New developments in the ANSYS TurboGrid software
are used to create high-quality meshes for bladed
components with minimal user input.
Geometry courtesy PCA Engineers.
Enhancements to
Turbomachinery Tools
With release 12.0, a number of
enhancements have been incorporated into ANSYS BladeModeler,
the design tool tailored to bladed
geometries for rotating machinery.
Within the BladeGen component,
the integrated tools for determining
initial blade shape and size (which
were developed in conjunction with
partner PCA Engineers Limited)
have been expanded to cover centrifugal compressors and axial fans
in addition to radial turbines and
centrifugal pumps. The other component of ANSYS BladeModeler,
BladeEditor, includes new blade
geometry modeling capabilities to
create and modify one or more
bladed components. As an add-in to
ANSYS DesignModeler, ANSYS
BladeModeler provides access to
ANSYS DesignModeler’s extensive
functionality to create nonstandard geometry components
and features.
ANSYS TurboGrid software
includes a number of evolutionary
improvements in release 12.0, and
introduces a completely new
meshing technology. This tool
fully automates a series of topology and smoothing steps to
largely eliminate the need to
manually adjust mesh controls,
yet still generates high-quality
fluid dynamics meshes for bladed
turbomachinery components.
www.ansys.com
12.0: MULTIPHYSICS
Multiphysics
for the Real World
In ANSYS 12.0, multiphysics capabilities continue to
increase in flexibility, application and ease of use.
Continuing to build on the foundation of prior releases,
ANSYS 12.0 expands the company’s industry-leading
comprehensive multiphysics solutions. New features and
enhancements are available for solving both direct and
sequentially coupled multiphysics problems, and the
ANSYS Workbench framework makes performing multiphysics simulations even faster than before.
ANSYS Workbench Integration
The integration of the broad array of ANSYS solver
technologies has taken a considerable step forward with
release 12.0. The ANSYS Workbench environment has been
redesigned for an efficient multiphysics workflow by integrating the solver technology into one unified simulation
environment. This platform now includes drag-and-drop
multiphysics, which allows the user to easily set up and
visualize multiphysics analysis, significantly reducing the
time necessary to obtain solutions to complex multiphysics
problems.
Another new enhancement to the ANSYS Workbench
framework is the support for steady-state electric conduction. There is a new analysis system that exposes 3-D solid
electric conduction elements (SOLID231 and SOLID232) in
the ANSYS Workbench platform. All the benefits of this
popular environment — leveraging CAD data, meshing
complex geometry and design optimization features — are
now available for electric conduction analysis.
Also new in ANSYS Workbench at version 12.0 is support for direct coupled-field analysis. Relevant elements
(SOLID226 and SOLID227) are now natively supported
in the ANSYS Workbench platform for thermal–electric
coupling. There also is a new analysis system for thermal–
electric coupling that supports Joule heating problems with
The electric potential for the transformer busbar shown here was analyzed within
the ANSYS Workbench environment and required the use of temperature-dependent
material properties. Courtesy WEG Electrical Equipment.
temperature-dependent material properties and advanced
thermoelectric effects, including Peltier and Seebeck effects.
The applications for this new technology include Joule
heating of integrated circuits and electronic traces,
busbars, and thermoelectric coolers and generators.
Solver Performance
ANSYS 12.0 extends the distributed sparse solver to
support unsymmetric and complex matrices for both shared
and distributed memory parallel environments. This new
solver technology dramatically reduces the time needed to
perform certain direct coupled solutions including Peltier and
Seebeck effects as well as thermoelasticity. Thermoelasticity, including thermoelastic damping, is an important
loss mechanism for many MEMS devices, such as block
resonators and silicon ring gyroscopes.
The project schematic shows the multiphysics workflow for a coupled electric conduction, heat transfer and
subsequent thermal stress analysis.
www.ansys.com
Elements
A new family of direct coupledfield elements is available in ANSYS
12.0; these new elements enable the
modeling of fluid flow through a
porous media. This exciting new
capability, comprising coupled
pore–pressure mechanical solids,
ANSYS Advantage • Volume III, Issue 1, 2009
11
12.0 MULTIPHYSICS
enables multiphysics modeling
of new classes of civil and biomedical engineering problems that rely
on fluid pore pressures. The elements
allow users to model fluid pore pressures in soils (for simulating building foundations)
and biometric materials (for modeling bone in order to
develop prosthetic implants).
Sequence of images showing simulation of the
motion of a screw pump solved using immersed
solid fluid structure interaction
4
Scale of Solution Speed
Fluid Structure Interaction
One of the major enhancements for fluid structure interaction (FSI) is a new immersed solid FSI solution. This
technique is based on a mesh superposition method in
which the fluid and the solid are meshed independently
from one another. The solution enables engineers to model
fluid structure interaction of immersed rigid solids with
imposed motion. Rotating, translating and explicit motion of
rigid–solid objects can be defined, and the CFD solver
accounts for the imposed motion of the solid object in the
fluid. This solution technique provides rapid FSI simulations,
since there is no need to morph or remesh the fluid mesh
based on the solid motion. The model preparation for the
new immersed solid technique is also very straightforward:
The entire setup for the FSI solution can be performed
entirely within ANSYS CFX software. This technology is
especially applicable to fluid structure interaction problems
with large imposed rigid-body motions, such as closing
valves, gear pumps and screw compressors. The method is
also useful for rapid first-pass FSI simulations.
3
2
1
1
2
3
4
5
6
7
8
9
10
11
12
Number of Processors
Solution scaling of a thermoelectric cooler model with
500,000 degrees of freedom enables a speedup of four
times for 12 processors.
Coupling Electromagnetics
simulation environment started almost immediately after
the acquisition. While the combined development team is
working toward a seamlessly integrated bidirectional
solution, several electromagnetic-centric case studies
already have demonstrated the ability
to couple electromagnetic, thermal
Start
and structural tools within the
adaptive architecture of the ANSYS
Workbench environment.
Create and solve the electromagnetic
Import the geometry into
For example, a high-power elecapplication using HFSS
ANSYS Mechanical and create the
corresponding ANSYS thermal model
tronic connector used in a radar
application to connect a transmitter to
an antenna must be engineered from
Export geometry and thermal link file
Import surface and/or volumetric
from HFSS to ANSYS Mechanical
electromagnetic, thermal and structural
losses using the imported load option
perspectives to ensure success. The
(beta) in ANSYS Workbench
simulation was performed by coupling
Ansoft’s HFSS software with the
ANSYS Workbench environment, using
Solve the ANSYS thermal model and
ANSYS Workbench runs HFSS in batch
End
post-process the thermal results
to perform the load interpolation
advanced thermal and structural capabilities. Engineers used HFSS to ensure
that the device was transmitting in the
Case study procedure of one-way coupling between Ansoft (blue) and ANSYS (yellow) software
By joining forces with Ansoft, ANSYS can deliver
greater multiphysics capabilities — specifically electromagnetics — to the ANSYS suite. The plan to integrate this
electromagnetics technology within the existing ANSYS
12
ANSYS Advantage • Volume III, Issue 1, 2009
www.ansys.com
12.0: MULTIPHYSICS
temperatures or surface forces between ANSYS FLUENT
and ANSYS mechanical products based on ANSYS CFXPost. The most appropriate applications include those that
require one-way transfer of fluid pressures or temperatures
from CFD to a mechanical analysis, such as automotive
exhaust manifolds, heat sinks for electronics cooling and
turbomachinery.
The results of an RF MEMS switch solved by coupling the electrostatic, fluid and
mechanical behavior of the switch in one analysis using FLUID136 to represent squeeze
film effects. Image courtesy EPCOS NL and Philips Applied Technologies.
Another new capability for fluid structure interaction in
ANSYS 12.0, FLUID136 now solves the nonlinear Reynolds
squeeze film equations for nonlinear transient FSI applications involving thin fluid films. Since the nonlinear fluidic and
structural responses are coupled at the finite element level,
the solution is very fast and robust for thin fluid film applications. Any squeeze film application can benefit from this
technology, including thin film fluid damping often found in
RF MEMS switches.
Version 12.0 offers another exciting new FSI capability:
the ability to perform one-way fluid structure interaction
using ANSYS FLUENT software as the CFD solver.
This capability enables one-way load transfer for surface
proper path, by calculating the high-frequency electromagnetic fields, power loss density distribution and
S-parameters. In such high-power applications, it is critical
to determine the temperature distribution to ensure the
device stays below temperatures that cause material failure,
such as melting. The power loss density results from the
HFSS simulation were used
as the source for the thermal
simulation performed within
ANSYS Mechanical software,
which simulated the temperature distribution of the device.
In another case, a valveactuating solenoid application
used a coupled ANSYS and
Ansoft simulation to analyze
temperature distribution.
Maxwell software was used to
calculate the power loss from
the low-frequency electroEddy current and conduction loss
calculated by Ansoft’s Maxwell software magnetic fields within the
Multi-Field Solver
The multi-field solver (used for performing implicit
sequential coupling) contains a number of new enhancements at release 12.0. The first is a new solution option that
controls writing a multiframe restart file. This capability
allows a user to restart an analysis from any multi-field time
step, which allows for better control over the availability of a
restart file with less hard drive usage. Another enhancement
is more-flexible results file controls. This capability reduces
the results file sizes for the multi-field solver, and it allows for
synchronizing the fluid and mechanical results in an FSI
solution. The final improvement is new convergence controls for the multi-field solution to provide more flexible
solution controls for nonlinear convergence of the multi-field
solver. The applications for these enhancements are any
multiphysics application using sequential coupling including
fluid structure interaction. ■
Stephen Scampoli of ANSYS, Inc. and Ansoft LLC technical specialists
contributed to this article.
Deformation of the high-power electronic connector can be predicted by combining
Ansoft HFSS and ANSYS Mechanical software.
solenoid. The power loss was used as an input for a thermal
simulation performed with ANSYS Mechanical software to
determine the temperature profile of the device. Subsequently, the application predicted how the device deformed
due to the rise in temperature. Such coupling delivers a
powerful analysis framework needed to solve these complex,
interrelated physics problems. Thus, engineers can
address electro-thermal-stress problems associated with
optimizing state-of-the-art radio frequency (RF) and electromechanical components including antennas, actuators,
power converters and printed circuit boards (PCBs).
ANSYS Advantage • Volume III, Issue 1, 2009
13
12.0: ELECTROMAGNETICS
ANSYS Emag 12.0
Generates Solutions
Improved accuracy, speed and platform integration advance
the capabilities of low-frequency electromagnetic simulation.
SOLID236
3-D 20-node brick
SOLID237
3-D 10-node
tetrahedron
As the combined development teams from Ansoft and
ANSYS set out to integrate the world-class Ansoft electronic
design products into the ANSYS portfolio, ANSYS
customers can benefit immediately from improved and
extended electromagnetics capabilities in release 12.0.
and SOLID237 elements support both distributed and
shared-memory parallel processing for low-frequency
electromagnetic solutions. As a result of faster simulation
speeds, users can solve much larger and more complex
low-frequency electromagnetic models.
Elements
A new family of 3-D solid elements for low-frequency
electromagnetic simulation is included in the 12.0 release of
ANSYS Emag software. Solid elements (SOLID236 and
SOLID237) are available for modeling magnetostatic, quasistatic time harmonic, and quasi-static time-transient
magnetic fields. These two elements are formulated using
an edge-based magnetic vector potential formulation,
which allows for improved accuracy for low-frequency
electromagnetic simulation. The elements also provide a
true volt degree of freedom — as opposed to a timeintegrated electric potential — enabling circuit coupling
with discrete circuit elements and simplifying preand post-processing for electromagnetic simulation.
SOLID236 and SOLID237 also include much faster
gauging than prior releases, which significantly reduces
overall solution times. Users can apply this new element
technology to most low-frequency electromagnetic
applications, such as electric motors, solenoids,
electromagnets and generators.
ANSYS Workbench Integration
Release 12.0 offers several ANSYS Workbench
enhancements for electromagnetic simulation. A new
capability facilitates multiple load step analysis for magnetostatics. This allows users to compute the magnetostatic
response to time-dependent loading, specifying voltage and
current loads with time-dependent
tabular data. The results are
more flexibility for magnetostatic problems with
time-dependent loads
along with transient
simulation for electromagnetics, with
the addition of a
simple command
snippet, within the
ANSYS Workbench
environment.
The integrated platNonlinear transient rotational test
form also includes an
rig solved in the ANSYS Workbench
environment using SOLID236, SOLID237
option for a meshed
and the new stranded conductor option
representation of a
(TEAM24 benchmark)
stranded conductor.
The current density for the new stranded conductor
supports tabular loading for the new multi-step magnetostatic analysis. This capability allows for a more
accurate representation of current, improves overall
simulation accuracy and leverages existing CAD data for
coil geometry. This new ANSYS Workbench technology
can be applied to any electromagnetic application
subject to time-dependent loading, including electric
machines, solenoids and generators. ■
Solvers
At release 12.0, the distributed sparse solver includes
support for low-frequency electromagnetics. SOLID236
DANSYS for Low-Frequency Electromagnetics
Solutions Speedup
5
4
3
2
1
1
3
4
5
6
7
Number of Processors
Solution scaling of a SOLID237 model with 550,000 degrees of freedom
14
2
ANSYS Advantage • Volume III, Issue 1, 2009
8
Stephen Scampoli of ANSYS, Inc. contributied to this article.
www.ansys.com
12.0: FLUIDS
A Flood of Fluids
Developments
A new integrated environment and
technology enhancements make fluids
simulation faster, more intuitive and
more accurate.
With release 12.0, ANSYS continues to deliver on its commitment to
develop the world’s most advanced
fluid dynamics technology and make
it easier and more efficient to use.
Through its use, engineers can
develop the most competitive products and manufacturing processes
possible. In addition to delivering
numerous new advancements in
physics, numerics and performance,
ANSYS has combined the functionality of both ANSYS CFX and ANSYS
FLUENT into the ANSYS Workbench
platform. Customers can use this
integrated environment to leverage
simulation technology, including
superior CAD connectivity, geometry
creation and repair, and advanced
meshing, all engineered to improve
simulation efficiency and compress
the overall design and analysis cycle.
Integration into ANSYS Workbench
ANSYS 12.0 introduces the full
integration of its fluids products into
ANSYS Workbench together with the
capability to manage simulation
workflows within the environment. This
allows users — whether they employ
ANSYS CFX or ANSYS FLUENT software (or both) — to create, connect
and re-use systems; perform automated parametric analyses; and
seamlessly manage simulations
using multiple physics all within
one environment.
The integration of the core CFD
products into the ANSYS Workbench
environment also provides users with
www.ansys.com
access to bidirectional CAD
connections, powerful geometry
modeling and advanced mesh generation. (See the article Taking Shape in
12.0.) Users can examine analysis
results in full detail using CFD-Post,
also available within the ANSYS
Workbench environment.
Multiphysics
In some cases, fluid simulations
must consider physics beyond basic
fluid flow. Both ANSYS CFX and
ANSYS FLUENT technologies provide
many multiphysics simulation options
and approaches, including coupling
to ANSYS Mechanical software to
analyze fluid structure interaction
(FSI) within the ANSYS Workbench
environment.
Another new capability is the
immersed solid technique in ANSYS
CFX 12.0 that allows users to include
the effects of large solid motion
in their analyses. (See the article
Multiphysics for the Real World.)
General Solver Improvements
ANSYS continues to make
progress on basic core solver speed, a
benefit to all users for all types of applications, steady or transient. A suite of
cases that span the range of industrial
applications has consistently shown
increases in solver speed of 10 to 20
percent, or even more, for both ANSYS
CFX and ANSYS FLUENT software.
Beyond core solver efficiency, improvements to various aspects of parallel
efficiency address the continued
Fuel injector model with close-up of vapor volume
fraction contours at the injector surface
growth and needs of high-performance
computing. (See the article The Need
for Speed.)
The perennial goal of improving
accuracy without sacrificing robustness
motivated numerous developments,
including new discretization options
such as the bounded second-order
option in ANSYS FLUENT and the
iteratively-bounded high-resolution
discretization scheme in ANSYS CFX.
Being able to consistently use higherorder discretization schemes means
that users will see further increases in
the accuracy of flow simulations without
penalties in robustness.
User Interface
Ease of use has been enhanced in
various ways. Most noticeably, the
ANSYS FLUENT user interface has
taken a significant step forward by
adopting a single-window interface
paradigm, consistent with other
applications integrated in ANSYS
Workbench. A new navigation pane
and icon bar and new task pages and
tools for graphics window management all reflect a more modern and
intuitive interface while providing
access to the previous version’s menu
bar and text user interface.
ANSYS Advantage • Volume III, Issue 1, 2009
15
12.0: FLUIDS
For ANSYS CFX software, a host
of improvements have been added to
the graphical user interface (GUI).
There is a completely new capability
that allows users to customize GUI
appearance, including the option to
create additional input panels. These
custom panels provide the ability
to encapsulate best practices
and common processes by giving
the user control over GUI layout and
required input.
Specific Focus Areas
Internal Combustion Engines
Internal combustion (IC) engines
are a primary target application for
the development of numerous
features. While this development is
driven by the specific needs of IC
engine simulations, it benefits many
other applications and users:
• New options and flexibility for
handling variations in physics
complexity required at different
phases of analyses
• Further-integrated options
and controls for remeshing,
including an IC-specific option
for setting up an entire engine
simulation
• Extensions and improvements
to discrete particle-tracking
capabilities
• Numerous enhancements to
combustion models and their
usability
Internal combustion engine simulation is one of the
focus applications for ANSYS 12.0. This snapshot from a
transient simulation of the complete engine cycle shows
the flow just after the intake valves open and the direct
injection of fuel. New flow feature extraction options in
CFD-Post are used to highlight vortex structures with
velocity vectors. Image courtesy BMW Group.
16
Evolution of the free surface of oil in a reciprocating compressor. The blue area is the gas/oil rotating domain inside
the shaft, and the gray surface at the bottom shows the oil level of the reservoir. As the shaft rotates, oil is pumped
up due to body forces. Image courtesy Embraco.
Multiphase
Multiphase flow modeling continues to receive a great deal of
development attention, in terms of
numerics and robustness improvements as well as extended modeling
capabilities. ANSYS FLUENT software
extends the single-phase coupling
technology, introduced previously for
the pressure-based solver, to include
Eulerian multiphase simulations. This
enhancement provides more robust
convergence, especially for steadystate flows. ANSYS CFX users will find
that improvements to the option to
include solution of the volume fraction
equations as part of the coupled set of
equations make it more broadly usable
in applications with separate velocity
fields for each phase. Other modeling
enhancements include the implementation of a wall boiling model and
additional non-drag forces in ANSYS
CFX as well as more robust cavitation
and immiscible fluid models in ANSYS
FLUENT.
Turbomachinery
The significant proportion of customers using products from ANSYS for
the design and optimization of rotating
machinery ensured that this field
received a substantial development
focus. This latest release contains a
variety of enhancements to core solver
technology that couple rotating and
stationary components more robustly,
more accurately and more efficiently.
ANSYS BladeModeler and ANSYS
TurboGrid, specialized products for
ANSYS Advantage • Volume III, Issue 1, 2009
bladed geometry design and mesh generation, continue to evolve and improve.
(See the Geometry and Meshing article
for more details.)
An exciting new development for turbomachinery analysts is the introduction of
the through-flow code ANSYS Vista™ TF.
Developed together with partner PCA
Engineers Limited, Vista TF complements
full 3-D fluid dynamics analysis to provide
basic performance predictions on one or
more bladed components in a matter of
seconds, allowing users to quickly and
easily screen initial designs.
And More …
These enhancements represent just
the tip of the iceberg in new and
improved models and capabilities within
core fluids products from ANSYS. Some
other new developments include:
• Turbulence modeling extensions
and improvements
■
Reynolds-averaged Navier–
Stokes (RANS) models
■
Laminar–turbulent transition
■
Large eddy simulation (LES)
■
Detached eddy simulation (DES)
■
Scale-adaptive simulation (SAS)
• Ability to use real gas properties
with the pressure-based solver in
ANSYS FLUENT and, therefore,
include these in reaction modeling
• Faster, more accurate chemistry
across the board
• Dramatic speedups in view factor
calculations in ANSYS FLUENT
www.ansys.com
12.0: FLUIDS
“ANSYS CFX 12.0 showed a
30 percent solver speedup
in comparison with the previous release. This significant improvement allows
us to examine more design variations in the same time, enabling further design
optimization and considerably reducing the total development time. This helps
Embraco bring our products to the market more quickly.”
— Celso Kenzo Takemori
Product and Process Technology Management
Embraco
• Inclusion of convective terms in
solids to model conjugate heat
transfer in moving solids in
ANSYS CFX
• Ability to model thin surfaces in
ANSYS CFX
• Much more in areas such as
particle tracking, fuel cells,
acoustics, material properties
and population balance methods
CFD-Post
An exciting introduction is the
common post-processing application
CFD-Post. The result of combining
technologies from both ANSYS
FLUENT and ANSYS CFX tools and
building upon the well-established
CFX-Post application, CFD-Post provides a complete range of graphical
post-processing options to allow users
to visualize and assess the flow predictions they have made and to create
insightful 2-D and 3-D images and
animations. The application includes
powerful tools for quantitative analysis,
such as a complete range of options for
calculating weighted averages and
automatic report-generation capabilities. All steps can be scripted, allowing
for fully automated post-processing.
Among the specific enhancements in
release 12.0 are the ability to open and
compare multiple cases in the same
CFD-Post session and the addition of
tools to locate vortex cores in the
predicted flow field.
In work sponsored by BMT Seatech, partially-filled tanks on marine vessels are being
simulated by researchers at the University of Southampton to predict structural loads
and changes in vessel behavior due to the sloshing of the fluid.
Conclusion
This is only a sampling of what the
fluid dynamics development teams
have produced for ANSYS 12.0. The
combined depth and breadth of
CFD knowledge and experience is
delivering benefits to all users as
technologies are combined and development teams drive simulation
technology to new levels of achievement. With release 12.0, ANSYS
continues its commitment to provide
leading-edge CFD technology. ■
This article was written through contributions
from Chris Wolfe and John Stokes of ANSYS, Inc.
CFD-Post can be used to compare multiple designs directly, both by examining
them side by side and by looking at the calculated difference between results.
Geometry courtesy CADFEM GmbH.
www.ansys.com
ANSYS Advantage • Volume III, Issue 1, 2009
17
12.0: STRUCTURAL MECHANICS
Warping and ovalization of pipe structures
with the new pipe elements
Designing with Structure
Advancements in structural mechanics allow more efficient and
higher-fidelity modeling of complex structural phenomena.
The ability to drive the engineering design process in
structural applications has taken a significant step forward
with the improvements in release 12.0. New features and
tools, many integrated into the ANSYS Workbench platform,
help reduce overall solution time. Specific improvements
focus on elements, materials and contact and solver
performance, along with linear, rigid and flexible dynamics.
this requires local remeshing during the simulation
process. The 2-D rezoning introduced with release 11.0
extends further in ANSYS 12.0, increasing the flexibility of
the remeshing process: The user can now define transition
regions within the refined zones and use meshes created
in external meshing tools.
Materials
Accounting for proper cyclic softening or hardening or
damage of materials is a key factor for elastomer applications and, more generally speaking, any structure whose
material variation depends on the strain rate. Release 12.0
introduces several additions to the wide choice of materials already available. Other feature improvements include:
• Rate-dependent Chaboche plasticity, which can
benefit turbine and engine design
Elements
The most notable new element in release 12.0 is the
four-noded tetrahedron for modeling complex geometries in
hyperelastic or forming applications. The element provides
a convenient way to automate the meshing of complex
structures, avoiding the need for pure hexahedral meshes.
This reduces the time it takes to develop a case from geometry through solution, while maintaining the accuracy of the
solution. See the table below for a summary of new and
enhanced elements.
When simulating a nonlinear process, large deformation
can introduce too much distortion of the elements. Resolving
Element
New
Improved
• Bergström–Boyce model to enhance elastomer
modeling capabilities
• New damage model based on the
Ogden–Roxburgh formulation
Capability
Applications
Four-noded tetrahedron
X
Provides a convenient way to automate
meshing of complex structures, avoiding
need for pure hexahedral meshes
Modeling complex geometries for forming or
hyperelastic applications
General axisymmetric element
X
Supports contact
Compatible with 3-D non-axisymmetric loading and can
use arbitrary axis of rotation
Various pipe model elements
X
Increased accuracy
To provide refined behavior of structures in case
of ovalization, warping or similar deformations of
cross section for thin or moderately thick pipes and
nonlinear material behavior support
Shell: linear, quadratic, axisymmetric
X
Improved shell thickness updating scheme
and improved convergence
Provides greater accuracy in the behavior of shell models
as well as a faster solution for nonlinear problems
Beam
X
Supports cubic shape function
Provides additional accuracy to coarse meshes and
greater support of complex load patterns
Reinforcement elements
X
Allows modeling of discrete fibers with a
variety of nonlinear material behavior
Stresses in reinforcements can be analyzed
separately from host elements
Summary of new and enhanced element features in ANSYS 12.0 structural analysis products
18
ANSYS Advantage • Volume III, Issue 1, 2009
www.ansys.com
12.0: STRUCTURAL MECHANICS
contact search algorithms, contact trimming logic and
smart over-constraint elimination for multipoint constraint
(MPC) contact.
Crack tip analysis
of turbine blade
Courtesy PADT
• Anand’s viscoplasticity model, useful for metal
forming applications such as solder joints
• Improvements in the calculation of J-integrals to
account for mixed-mode stress intensity factors,
which benefit improvements in fracture mechanics
Solver Performance
Solver performance has improved in many different
areas. ANSYS 12.0 introduces a new modal solver, called
SNODE, that increases the speed of computation for problems with a large number of modes — in the realm of
several hundred — on large structures that typically have
over a million degrees of freedom. This solver is well suited
for automotive or aerospace applications and for large
beams and shell assemblies. Beyond its ability to compute
a larger number of modes in a reduced amount of time,
SNODE also significantly reduces the amount of I/O
required to compute the solution. (See the Supernode
Eigensolver article.)
Many enhancements have been made to the distributed
solver to improve the scalability of the solution. (See
the article on High Performance Computing.) More solver
techniques are supported, including:
• Partial solve capability that computes only a portion
of the solution
• Prestressed analysis
• Initial strain and initial plastic stress import
capabilities that allow for state transfer from
a 2-D model to a 3-D model
www.ansys.com
These new features can be combined for applications
such as brake squeal, which might combine the partial
solve and unsymmetric matrix capabilities.
80,000
CPU Time (seconds)
Contact
As assemblies have become a de facto standard in
simulation, the need for advanced contact features has
grown accordingly. ANSYS 12.0 developments include a
number of additional contact modeling features as well as
significant improvements in solving contact problems.
While Coulomb’s law for friction is widely used, there are
circumstances in which more elaborate modeling is
required, such as wear modeling or pipelines resting on sea
beds. Release 12.0 supports a friction coefficient definition
that depends upon the contact state itself and accounts for
complex frictional behavior. Specifically, the user is able to
define the dependency of the friction on contact parameters, such as sliding distance or contact pressure.
A typical contact application involves seals that are subject to fluid pressure. Release 12.0 provides support of fluid
pressure penetration, to model scenarios in which pressure
rises higher than the contact pressure around the seal.
Pressures in such cases can be applied only on the free
faces of the structure and evolve with the contact state.
Contact simulation is usually a time-consuming
process. The latest release introduces contact modeling
improvements that significantly reduce computation time
and results file size. These enhancements include new
• Models that employ the use of unsymmetric
matrices, which are useful for scenarios that involve
high-friction coefficients, for example
60,000
Block Lanczos
Supernode
40,000
20,000
0
100
1,000
4,000
8,000
Number of Modes
Performance of new modal solver
Linear Dynamics
Some of these element, material, contact and solver
improvements benefit the field of linear dynamics as well.
They are complemented by enhancements specific to this
simulation area, especially for mode superposition analysis.
For harmonic or transient loadings, the mode superposition
methods exhibit better performance, especially during the
ANSYS Advantage • Volume III, Issue 1, 2009
19
12.0: STRUCTURAL MECHANICS
so-called expansion pass that computes results at each
frequency or time step on the full model. For very large
structures, the total computation effort can be reduced
by up to 75 percent. The mode combination for spectral
analysis benefits from similar advancements. Instability
predictions, such as the case of brake squeal, can be
computed faster due to several enhancements to the
damped eigensolver.
The introduction of ANSYS Variational Technology
provides faster mode computation for cyclic symmetric
structures, such as those found in many turbine
applications. Using this technique can typically improve
Instability analysis for brake squeal
Modal analysis of a
cyclic–symmetric geometry
Courtesy PADT, Inc.
solution speed by a factor of three or four — the greater the
number of sectors, the better the performance.
Rotating machinery applications profit from an extended
set of capabilities for rotordynamics analysis. These include
the extension of the gyroscopic effect to shell and
2-D elements and inclusion of rotating damping that takes
hysteretic behavior into account.
Random vibration and spectral analysis users gain new
tools as well as a greater flexibility in modeling structures,
including support of spectrum analysis in the ANSYS
Workbench platform. New tools include the United States
Nuclear Regulatory Commission–compliant computation of
missing masses and support of rigid modes, along with the
ability to use residual vectors to account for higher
energy modes. The global number of spectra applied
simultaneously to the structure has been increased up to
50 as has the number of modes used in a combination —
now up to 10,000.
When analyzing design variations, comparing data
from different simulation cases, or correlating simulation
and test data, comparison between modal content of the
models is required. The modal assurance criterion (MAC)
in release 12.0 provides a convenient tool to compare the
results of two modal analyses. Typical use cases for the
criteria include tuning of misaligned turbine blades or
validation of new component designs, each with respect
to their vibration behavior.
New Element Reduces Meshing Time
ZF Boge Elastmetall GmbH develops, manufactures and
supplies vibration control components and parts for the
automotive industry. These components include plastic
parts, energy-absorbing elements for vehicle safety, and
rubber–metal components such as chassis suspension
mounts, control arm bushes (also known as bushings) and
engine mounts.
The German company uses simulation to reduce
development time and costs. When developing models for
components with hyperelastic material properties, company
engineers require an element type that can be freely
meshed; can accommodate extreme deformation, stable
contact and short computing time; and can provide
reliable results.
By using the new SOLID285 four-noded tetrahedron element available in ANSYS 12.0, ZF Boge
Elastmetall engineers considerably reduced meshing
time. Close correlation between the simulation and physical
measurement allowed them to determine the spring rate of
strongly deformed structures without the complex and
20
ANSYS Advantage • Volume III, Issue 1, 2009
time-consuming meshing that was previously required
when using hexahedral elements. Boge’s work proved that
by employing this new element, users can determine
the stresses and strains for a durability calculation in a
reasonable time.
Deformation of
an automotive
suspension
mount
www.ansys.com
12.0: STRUCTURAL MECHANICS
ANSYS Workbench Integration
The integration of the structural applications within
the ANSYS Workbench platform provides additional
productivity to users, including:
• New meshing techniques to improve mesh quality
• Support of additional elements, such as gasket
elements as well as quadratic shells and beams
that include offset definitions
• Boundary condition definitions that provide a
spatial dependency for loads
• Coupling conditions
• Remote points
• Ability to associate contact to the top or bottom
of shell face
Post-processing capabilities have drastically improved
with release 12.0. The user can now plot any structural simulation data stored in the results files. Mathematical
operations involving elementary results can be introduced
to create additional user-defined criteria. Complex mode
shapes, plotting on linear paths, stress linearization (which
depends upon path plotting), and the ability to display
unaveraged results at element nodes complement the list of
the features that increase productivity at ANSYS 12.0. ■
Pierre Thieffry and Siddharth Shah of ANSYS, Inc. contributed to
this article.
Multibody Dynamics
At release 12.0, a number of improvements in the
general area of multibody dynamics enable the rapid design
and analysis of complete mechanical systems undergoing
large overall motion. ANSYS Rigid Dynamics software has a
new Runge–Kutta 5 integrator, the preferred solution for long
transient simulations. A new bushing joint, a “stops and
locks” option for most other joint types, and the ability
to specify preload for springs give new flexibility when
simulating complex multiple-part assemblies and
component interactions.
For complex assemblies, conducting an initial simulation
with the ANSYS Rigid Dynamics product is the key to
achieving robust flexible dynamics results. Creating overconstrained assemblies is an inconvenient reality; release
12.0 adds a redundancy analysis and repair tool to identify
overconstrained assemblies, points out which joints or
degrees of freedom are redundant, and allows selective
unconstraining to create a properly constrained mechanism.
A number of improvements to data and process
handling increase ease of use for multibody simulations:
• Ability to export forces and moments at any time
within a transient simulation
For durability studies, exported loads can be used in a
static structural analysis as an efficient first-pass failure
analysis. Although it won’t provide the complete picture
obtained from comprehensive flexible dynamics simulation,
a static structural simulation is typically much less computationally expensive. Flexible dynamics simulations benefit
at release 12.0 from robust component modal synthesis, or
CMS. This method uses an internal substructuring
approach and requires that the CMS parts of an assembly
are constructed with linear materials. The procedure simplifies a problem by accounting only for a few degrees of
freedom, which results in solution times that are often a
fraction of those found using the standard full computation
method. Time-to-solution reductions of several hundred
percent are not uncommon.
• Enhanced load data fitting (no longer requires
curve fitting)
• Ability to read in complex load input,
such as simulated or measured
multi-channel road surface or seismic
data, and apply as load data to parts
or joints
• Ability to use remote solution manager
(RSM) to offload the solving effort to a
server or other capable CPU (benefits longduration and multi-channel input transient
simulations)
Multibody dynamics capabilities were used to simulate this leaf spring suspension.
www.ansys.com
ANSYS Advantage • Volume III, Issue 1, 2009
21
12.0: EXPLICIT DYNAMICS
Explicit Dynamics
Goes Mainstream
ANSYS 12.0 brings native explicit dynamics to ANSYS Workbench
and provides the easiest explicit software for nonlinear dynamics.
ANSYS has expended significant
effort in the area of explicit dynamics for
release 12.0 — including the addition of
a new product that will make this technology accessible to users independent
of their simulation experience. In addition, enhancements to both the ANSYS
AUTODYN and ANSYS LS-DYNA
products provide considerable benefits
to their users.
Newly introduced in ANSYS 12.0,
ANSYS Explicit STR software is the first
explicit dynamics product with a native
ANSYS Workbench interface. It is based
on the Lagrangian portion of the ANSYS
AUTODYN product. The technology will
appeal to those who want to model
transient dynamic events such as drop
tests, as well as quasi-static events
involving rapidly changing contact
conditions, sophisticated material
failure/damage and/or severe displacements and rotations of structures. In
addition, it will appeal to users who can
benefit from the productivity provided by
other applications integrated within the
ANSYS Workbench environment.
Those who have previous experience
using ANSYS Workbench will find that
they already know most of what is
needed to use ANSYS Explicit STR.
The ANSYS Explicit STR tool is well
suited to solving:
• Drop tests (electronics and
consumer goods)
• Low- to high-speed solid-to-solid
impacts (a wide range of applications from sporting goods to
aerospace)
• Highly nonlinear plastic
buckling events (for ultimate
limit state design)
• Complete material failure
applications (defense and
homeland security)
• Breakable contact, such as
adhesives or spot welds
(electronics and automotive)
The real benefit of ANSYS Explicit
STR software is the work flow afforded
by operating in the ANSYS Workbench
environment. While many different
simulation processes are possible, here
is an example of the typical steps a user
might take:
• Associatively link to a parametric
CAD model or import a geometry
• Create a smooth explicit mesh
using the new explicit preference
option and/or patch-independent
mesh method within the ANSYS
meshing platform; automatically
create part-to-part contact by using
the new body interactions tool
• Fine-tune contact specifications if
desired by utilizing breakable or
eroding contact options
• Load and/or support an assembly
and/or parts as usual
• Assign material properties from the
comprehensive material library
• Solve interactively either in the
background or via remote solution
manager (RSM)
• View progress of solution in real
time using concurrent postprocessing capability, new to
ANSYS Workbench at 12.0
• Explore alternative design ideas
via parametric changes to the CAD
model and easily perform re-solves,
just like other ANSYS Workbench
based applications
• Use the ANSYS Design Exploration
capability to automate the parametric model space exploration
In addition, users of the full version of
ANSYS AUTODYN (structural- plus fluidscapable) have access to the ANSYS
Explicit STR interface; consequently, they
will be able to transfer implicit solutions
from the ANSYS Workbench environment
for doing implicit–explicit solutions, such
as bird strike analysis of a pre-stressed fan
blade. ANSYS LS-DYNA software users
will be able to use the pre-processing
portion of ANSYS Explicit STR and output
a .K file for solving and post-processing
outside of ANSYS Workbench. ■
ANSYS Explicit STR is the first explicit dynamics product with a native ANSYS Workbench interface.
22
ANSYS Advantage • Volume III, Issue 1, 2009
Wim J. Slagter of ANSYS, Inc. is available to
answer your questions about explicit dynamics.
www.ansys.com
12.0: EIGENSOLVER
Introducing the
Supernode Eigensolver
A new eigensolver in ANSYS 12.0 determines large numbers of natural
frequency modes more quickly and efficiently than conventional methods.
In a wide range of applications, parts are subject to
cyclic mechanical loading, and engineers must use an
eigensolver to determine the structure’s natural frequencies
— also known as eigen modes. With some modes, large
vibration amplitudes can interfere with product performance
and cause damage, such as fatigue cracking. In most
cases, only the first few modes with the largest deformations are of particular interest, though determining even
dozens of modes can be common.
In the CAE industry, the block Lanczos eigensolver is
typically used more than any other for these types of calculations. This proven algorithm has been used in many finite
element software packages, including ANSYS Mechanical
technology. It brings together the efficiency and accuracy of
the Lanczos algorithm and the robustness of a sparse direct
equation solver. The software works in a sequential fashion
by computing one mode (or a block of modes) at a time until
all desired modes have been computed.
Although the method is considered efficient in solving
for each of these eigen modes, the amount of time and
computer resources (both memory and I/O) required adds
up when many dozens of eigen modes must be found.
Elapsed solution times of several hours — or days — are
typical in applications that involve thousands of modes.
Generally, determining large numbers of modes is required
in capturing system response for studies such as transient
or harmonic analyses using the mode superposition
method.
© istockphoto.com/Matejay
By Jeff Beisheim, Senior Development Engineer, ANSYS, Inc.
The ANSYS supernode eigensolver is well suited for applications such as seismic
analysis of power plant cooling towers, skyscrapers and other structures in which
hundreds of modes must be extracted to determine the response of the structures
to multiple short-duration transient shock/impact loadings.
For such cases, the ANSYS release 12.0 includes a new
supernode eigensolver. Instead of computing each mode
individually and working with mode shapes in the global
model space, the supernode algorithm uses a mathematical
approach based on substructuring to simultaneously determine all modes within a given frequency range and to
manage data in a reduced model space.
By utilizing fewer resources than block Lanczos, this
supernode eigensolver becomes an ideal choice when
solving on a desktop computer, which can have limited
memory and relatively slow I/O performance. When combined with current eigensolver technology already available
in mechanical software from ANSYS, virtually all modal
analyses can be efficiently solved.
Comparing Eigensolvers
A sample comparison shows that the supernode eigensolver offers no significant performance
advantage over block Lanczos for a low number of
modes. In fact, supernode is slower when 50
or fewer modes are requested. However, when
more than 200 modes are requested, the
supernode eigensolver is significantly faster
than block Lanczos — with efficiency increasing
considerably as the number rises.
Solver Elapsed Time (seconds)
25,000
Linux 64-bit server: 3.4 GHz
single-core Xeon®, Red Hat® 4,
64 GB RAM, 200 GB disk
20,000
15,000
Block Lanczos
Supernode
10,000
5,000
0
10
50
100
200
500
Number of Requested Modes
1,000
2,000
Performance of block Lanczos and supernode eigensolvers at 1 million DOF
www.ansys.com
ANSYS Advantage • Volume III, Issue 1, 2009
23
12.0: EIGENSOLVER
Using Supernode Eigensolver
The supernode eigensolver can be selected in the
ANSYS Mechanical traditional interface using the SNODE
label with the MODOPT command or via the Analysis Options
dialog box. ANSYS Workbench users can choose this
eigensolver by adding a command snippet that includes the
MODOPT,SNODE command.
The MODOPT command allows users to specify the number of natural frequencies and what range those frequencies
lie within. With other eigensolvers, the number of requested
modes primarily affects solver performance, while the frequency range is, essentially, optional. Asking for more
modes increases solution time, while the frequency range
generally decides which computed modes are computed.
The supernode eigensolver behaves completely opposite: It computes all modes within the specified frequency
range regardless of how many modes are requested.
Therefore, for maximum efficiency, users should input
a range that covers only the spectrum of frequencies
between the first and last mode of interest. The number
of modes requested on the MODOPT command then
decides how many of the computed frequencies are
provided by the software.
Today, with the prevalence of multi-core processors, the
first release of this new eigensolver will support sharedmemory parallelism. For users who want full control of the
solver, a new SNOPTION command allows control over
several important parameters that affect accuracy and
efficiency.
Controlling Parameters
The supernode eigensolver does not compute exact
eigenvalues. Typically, this is not an issue, since the lowest
modes in the system (often used to compute the dominant
resonant frequencies) are computed very accurately — generally within less than 1 percent compared to using block
Lanczos. Accuracy drifts somewhat with higher modes,
however, in which computed values may be off by as much
as a few percent compared with Lanczos. In these cases,
the accuracy of the solver may be tightened using the range
factor (RangeFact) field on the SNOPTION command.
Higher values of RangeFact lead to more accurate solutions at the cost of extra computations that somewhat slow
down eigensolver performance.
When computing the final mode shapes, the supernode eigensolver often does the bulk of I/O transfer to and
from disk, and the amount of I/O transfer is often
significantly less than a similar run using block Lanczos. To
maximize supernode solver efficiency, I/O can be further
minimized using the block size (BlockSize) field on the
SNOPTION command. Larger values of block size will
reduce the amount of I/O transfer by holding more data in
memory during the eigenvalue/eigenvector output phase,
which generally speeds up the overall solution time.
However, this is recommended only if there is enough
physical memory to do so.
Application Guidelines
The following general guidelines can be used in determining when to use the supernode eigensolver, which is
typically most efficient when the following three conditions
are met:
• The model would be a good candidate for using the
sparse solver in a similar static or full transient
analysis (that is, dominated with beam/shell elements
or having thin structure).
• The number of requested modes is greater than 200.
• The beginning frequency input on the MODOPT
command is zero (or near zero).
For models that have dominantly solid elements or
bulky geometry, the supernode eigensolver can be more
efficient than other eigensolvers, but it may require higher
numbers of modes to consider it the best choice. Also,
other factors such as computing hardware can affect the
decision. For example, on machines with slow I/O performance, the supernode eigensolver may be the better choice,
even when solving for less than 200 modes. ■
Examining Real-World Performance
A heavy-equipment cab model with over 7 million equations was
used to demonstrate the power of the supernode eigensolver. This
model was solved using a single core on a machine with the
Windows® 64-bit operating system with 32 gigabytes of RAM. Time
spent computing 300 modes with block Lanczos was about 31.8
hours. The solution time dropped to 15.7 hours (a two-times
speedup) using the supernode eigensolver. The model illustrates
real-world performance for a bulkier model with only 300 modes
requested. For modal analyses in which hundreds or thousands of
modes are requested, users often see a speedup of 10 times or more
with the supernode eigensolver compared with block Lanczos. In
one recent project, a major industrial equipment manufacturer
reduced analysis run time from 1.5 hours to just 10 minutes by
switching from block Lanczos to supernode eigensolver.
24
ANSYS Advantage • Volume III, Issue 1, 2009
Total displacement for the tenth-lowest natural
frequency is plotted for a heavy-equipment cab model
represented by more than 7 million equations.
Model courtesy PTC.
www.ansys.com
12.0: HIGH-PERFORMANCE COMPUTING
The Need for Speed
From desktop to supercomputer, high-performance computing with
ANSYS 12.0 continues to race ahead.
Tuning software from ANSYS on the latest highperformance computing technologies for optimal performance
has been — and will continue to be — a major focus area
within the software development organization at ANSYS. This
effort has yielded significant performance gains and new
functionality in ANSYS 12.0, with important implications for
more productive use of simulation by customers.
High-performance computing, or HPC, refers to the use of
high-speed processors (CPUs) and related technologies to
solve computationally intensive problems. In recent years,
HPC has become much more widely available and affordable, primarily due to the use of multiple low-cost
processors that work in parallel on the computational
task. Today, clusters of affordable compute servers make
large-scale parallel processing a very viable strategy for
ANSYS customers. In fact, the new multi-core processors have turned even desktop workstations into
high-performance platforms for single-job execution.
This wider availability of HPC systems is enabling
important trends in engineering simulation. Simulation models are getting larger — using more
computer memory and requiring more
computational time — as engineers
include greater geometric detail and
more-realistic treatment of physical phenomena (Figure 1). These higher-fidelity models are critical for
simulation to reduce the need for expensive physical testing.
HPC systems make higher-fidelity simulations practical by
yielding results within the engineering project’s required time
frame. A second important trend is toward more simulations
— enabling engineers to consider multiple design ideas,
conduct parametric studies and even perform automated
design optimization. HPC systems provide the throughput
required for completing multiple simulations simultaneously,
thus allowing design decisions to be made early in the project.
Software from ANSYS takes advantage of
multi-processor and/or multi-core systems by employing
domain decomposition, which divides the simulation model
into multiple pieces or sub-domains. Each sub-domain is then
computed on a separate processor (or core), and the multiple
processors work in parallel to speed up the computation. In the
ideal case, speedup is linear, meaning that the simulation turnaround time can be reduced in proportion to the number of
processors used. Parallel processing also allows larger
problems to be tackled, since the processing power and
memory requirements can be distributed across the cluster of
processors. Whether performed on a multi-core desktop workstation, desk-side cluster or scaled-out HPC system, parallel
www.ansys.com
Figure 1. Simulations as large as 1 billion cells are now supported at release 12.0.
This 1 billion-scale racing yacht simulation was conducted on a cluster of 208 HP
ProLiant™ server blades. (For more information, visit www.ansys.com/one-billion.)
Image courtesy Ignazio Maria Viola.
HPC on Workstations?
While purists might argue whether workstations can
be considered high-performance computing platforms,
the performance possibilities for ANSYS 12.0 running on
workstations are noteworthy. With the latest quad-core
processor technology, an eight-core workstation running
Windows® can deliver a speedup of five to six times for
users of mechanical products from ANSYS (Figure 2)
and over seven times for users of its fluid dynamics
products (Figure 4). This means that parallel processing
now provides tremendous ROI for both large engineering
groups and individual workstation users, enabling faster
turnaround, higher-fidelity models and parametric
modeling. With release 12.0 and 2009 computing
platforms, parallel processing improves productivity
for all simulation types, from workstation to cluster, for
mechanical or fluids simulations.
ANSYS Advantage • Volume III, Issue 1, 2009
25
12.0: HIGH-PERFORMANCE COMPUTING
8.83
8.00
9.00
8.00
5.74
Core Solver Speedup
7.00
5.46
5.53
6.00
5.83
5.00
4.55
4.00
3.00
2.00
1.00
0.00
8
al
Ide
D-2
BM
4
D-3
BM
res
Co
of
r
e
mb
Nu
2
D-4
BM
D-5
BM
D-6
BM
1
D-7
BM
Core Solver Speedup
Figure 2. Speedup of Distributed ANSYS Mechanical 12.0 software using the
11.0 SP1 benchmark problems. Simulations running eight-way parallel show typical
speedup of between five and six times. Data was collected on a Cray CX-1 Personal
Supercomputer using two quad-core Intel Xeon Processor E5472 running Microsoft®
Windows HPC Server 2008.
80
70
60
50
40
30
20
10
0
1
2
4
8
32
Number of Cores
64
128
Figure 3. Scaling of a 10M DOF simulation using the ANSYS Mechanical 12.0 iterative
PCG solver on a cluster of Intel Xeon 5500 Processor series. All cores on these quadcore processors are fully utilized for the benchmark.
8.00
8.00
Core Solver Speedup
7.00
7.58 7.55
7.16 7.18
6.23
6.79
6.47
6.00
5.00
4.00
3.00
2.00
1.00
0.00
al
Ide L5L2
L3
F
4M
FL5
an_
14M
ar
Sed
ck_
yC
e
ans
Tru
Ind
ANSYS
bin
LeM
FLUEN
Tur
T
ANSYS
CFX
8
4
2
1
s
ore
fC
ro
e
mb
Nu
Figure 4. Scalability of ANSYS FLUENT and ANSYS CFX benchmark problems on the
Intel Xeon 5500 Processor series quad-core platform. Simulations running eight-way
parallel show typical speedup of over seven times.
26
ANSYS Advantage • Volume III, Issue 1, 2009
processing provides excellent return on investment by improving
the productivity of the engineers who perform simulation.
ANSYS 12.0 provides many important advances in areas
related to parallel processing and HPC, delivering scalability
from desktop systems to supercomputers. For users of the
ANSYS Mechanical product line, release 12.0 introduces
expanded functionality in the Distributed ANSYS (DANSYS)
solvers, including support for all multi-field simulations, prestress effects and analyses involving cyclic symmetry. In
addition, DANSYS now supports both symmetric and nonsymmetric matrices as well as all electromagnetic analyses.
Mechanical simulations benefit from significantly improved
scaling on the latest multi-core processors. Simulations in the
size range of 2 million to 3 million degrees of freedom (DOF)
now show good scaling on eight cores (Figure 2). Based on
benchmark problem performance, customers can expect to
get answers back five to six times faster on eight cores. Even
more impressive is the scale-out behavior shown in Figure 3,
with a 10 million DOF simulation showing solver speedup of
68 times on 128 cores.
With turnaround times measured in tens of seconds,
parametric studies and automated design optimization are
now well within the grasp of ANSYS customers who perform
mechanical simulations. These benchmarks are noteworthy,
in part, as they show execution with all cores on the cluster
fully utilized, indicating that the latest quad-core processors
have sufficient memory bandwidth to support parallel
processing for memory-hungry mechanical simulations.
Software tuning has contributed to improved scaling as well,
including improved domain decomposition, load balancing
and distributed matrix generation. To help customers maximize their ANSYS solver performance, the online help system
now includes a performance guide that provides a comprehensive summary of factors that impact the performance of
mechanical simulations on current hardware systems.
Explicit simulations using ANSYS AUTODYN technology
take great advantage of HPC systems at release 12.0. Full
64-bit support is now available, allowing much larger simulations to be considered from pre-processing to solution and
post-processing.
For users of fluid dynamics software from ANSYS, release
12.0 builds on the strong foundation of excellent scaling in
both the ANSYS FLUENT and ANSYS CFX solvers. These
fluids simulation codes run massively parallel, with sustained
scaling at hundreds or even thousands of cores. The release
incorporates tuning for the latest multi-core processors,
including enhanced cache re-utilization, optimal mapping and
binding of processes to cores (for better memory locality and
system utilization), and leveraging the latest compiler optimizations. The resulting ANSYS FLUENT and ANSYS CFX
performance on the newly released Intel ® Xeon ® 5500
Processor series is shown in Figure 4, with outstanding
speedup of over seven times for many benchmark cases. In
addition, the new release delivers significant performance
improvements at large core counts, the result of general
solver enhancements and optimized communications over
the latest high-speed interconnects. Figure 5 demonstrates
www.ansys.com
12.0: HIGH-PERFORMANCE COMPUTING
120.00
100.00
Speedup
80.00
Transonic Airfoil Benchmark
Model — 10M Nodes
60.00
40.00
Ideal
Infiniband
20.00
0.00
Gigabit
0
16
32
48
64
80
96
Number of Cores
Figure 5. Scalability of ANSYS CFX 12.0 on a 10M node transonic airfoil benchmark
example. Data was collected on a cluster of AMD Opteron™ 2218 processors, showing
the benefit of a high-speed interconnect.
2,048
Solver Speedup
1,536
1,581
Truck Benchmark Model —
111M Cells
1,024
991
512
Speedup
Ideal
521
265
0
128
0
512
1,024
1,536
2,048
Number of Cores
Figure 6. Scaling of ANSYS FLUENT 12.0 software is nearly ideal up to 1,024 processors
and 78 percent of ideal at 2,048 processors. Data courtesy SGI, based on the SGI Altix®
ICE 8200EX using quad-core Intel Xeon Processor E5472 with Infiniband®.
I/O Rate for Data Write (MBytes/sec)
scaling achieved by ANSYS CFX software on a cluster of
quad-core AMD processors. Nearly ideal linear scaling to
1,024 cores — and very good efficiency up to 2,048 cores —
has been demonstrated with ANSYS FLUENT (Figure 6). Both
fluids codes provide improvements to mesh partitioning that
enhance scalability. ANSYS FLUENT software now provides
dynamic load balancing based on mesh- and solutionderived criteria. This enables optimal scalability for
simulations involving multiphysics, such as particle-laden
flows. The ANSYS CFX code delivers improved partitioning
for moving and/or rotating meshes, yielding important
reductions in memory use and improved performance for
turbomachinery and related applications. Finally, ANSYS
FLUENT users will benefit from several usability improvements, including built-in tools for checking system network
bandwidth, latency and resource utilization — all helping to
identify potential scaling bottlenecks on the cluster.
Beyond solver speedup, the ANSYS 12.0 focus on HPC
addresses issues related to file input and output (I/O). Both
ANSYS FLUENT and ANSYS CFX software have updated I/O
algorithms to speed up writing of results files on clusters,
enhancing the practicality of periodic solution snapshots
when checkpointing or running time-dependent simulations.
ANSYS FLUENT includes improvements in the standard file I/O
as well as new support for fully parallel I/O based on parallel file
systems. Order of magnitude improvements in I/O throughput
have been demonstrated on large test cases (Figure 7), virtually
eliminating I/O as a potential bottleneck for large-scale simulations. ANSYS CFX improves I/O performance via data
compression during the process of gathering from the cluster
nodes, therefore reducing file write times. Proper I/O configuration is also an important aspect of cluster performance for the
ANSYS Mechanical product line.
Recognizing that cluster deployment and management
are key concerns, ANSYS 12.0 includes a focus on compatibility with the overall HPC ecosystem. ANSYS products are
registered and tested as part of the Intel Cluster Ready program, confirming that these products conform to standards of
compatibility that contribute to successful deployment
(www.ansys.com/intelclusterready). In addition to supporting
enterprise Linux® distributions from Red Hat® and Novell,
ANSYS 12.0 products are supported on clusters based on
Microsoft Windows HPC Server 2008. ANSYS has also
worked with hardware OEMs, including HP®, SGI®, IBM®, Dell®,
Cray® and others, to define reference configurations that are
optimally designed to run simulation software from ANSYS
(www.ansys.com/reference-configs).
As computing technology continues to evolve, ANSYS is
working with HPC leaders to ensure support for the breakthrough capability that will make simulation more productive.
Looking forward, important emerging technologies include
many-core processors, general purpose graphical processing
units (GP-GPUs) and fault tolerance at large scale. ■
400
PanFS
PanFS –—FLUENT
FLUENT1212.0
NFS
NFS –—FLUENT6.3
FLUENT6.3
300
345
334
273
200
39X
31X
20X
100
0
64
128
Number of Cores
256
Figure 7. Parallel I/O in ANSYS FLUENT 12.0 using the Panasas© file system, compared
to serial I/O in the previous release using NFS. Parallel treatment of I/O provides
important speedup for time-varying simulations on large clusters.
Contributions to this article were made by Barbara Hutchings,
Ray Browell and Prasad Alavilli of ANSYS, Inc.
www.ansys.com
ANSYS Advantage • Volume III, Issue 1, 2009
27
12.0: FUTURE DIRECTIONS
Foundations
for the Future
The many advanced features of ANSYS 12.0 were designed to solve
today’s challenging engineering problems and to deliver a platform for
tomorrow’s simulation technology.
As this special spotlight in ANSYS Advantage attests,
release 12.0 delivers a compelling advancement in what the
CAE industry has, until now, only envisioned — a full range
of best-in-class simulation capabilities assembled into a
flexible multiphysics simulation environment specifically
designed to increase engineering insight, productivity and
innovation. Whether the need is structural analysis, fluid
flow, thermal, electromagnetics, geometry preparation or
meshing, ANSYS customers can rely on release 12.0 for the
depth and breadth of simulation capabilities to overcome
their engineering challenges.
Staying true to our commitment to develop the most
advanced simulation technologies, release 12.0 has further
expanded the depth of individual physics and more
intimately coupled them to form an engineering simulation
capability second to none. A multitude of new material
models, physics and algorithms enable simulating
real-world operating conditions and coupled physical
phenomena, while new solver technology and parallel
processing improvements have dramatically reduced run
times and made complete system simulations more
computationally affordable.
Shouldering the array of technology in release 12.0
is our next-generation simulation platform, ANSYS
Workbench 2.0. Seamlessly spanning all stages of
engineering simulation, ANSYS Workbench 2.0 has been
engineered to manage the complexities of today’s simulations and to accelerate innovation.
28
ANSYS Advantage • Volume III, Issue 1, 2009
Release 12.0 is a notable milestone in the company’s
nearly 40-year history of innovating engineering simulation,
and it sets the stage for a new era of Smart Engineering
Simulation — an era in which ANSYS customers will gain
more from their investment in simulation by increasing the
efficiency of their processes, increasing the accuracy of
their virtual prototypes, and capturing and reusing their
simulation processes and data. However, the advancements of ANSYS 12.0 notwithstanding, the journey is far
from complete. To address the simulation challenges on the
horizon, ANSYS will continue to reinvest in research and
development and to explore new technologies. In particular,
there are a few areas that we consider vital in the pursuit of
Simulation Driven Product Development — areas in which
ANSYS has laid strong foundations and remains committed
to build upon as we look beyond release 12.0.
Physics First
ANSYS customers rely heavily on simulation before
making commitments to product designs or manufacturing
processes. High-fidelity engineering simulation is absolutely
paramount when upstream engineering decisions can
determine the overall success of a product and, in some
cases, the company’s financial success. At ANSYS, we
believe our customers should never have to compromise by
making broad-based engineering assumptions due to
limitations in their analysis software. That is why we have
taken a comprehensive multiphysics approach to simulation, and it starts with a foundation of individual physics.
Looking beyond release 12.0, ANSYS will continue to invest
and demonstrate leadership in all the key physics. And as
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12.0: FUTURE DIRECTIONS
we develop tomorrow’s advanced capabilities, we will continue to allow them to be combined in ways that free
engineers from making the assumptions associated with
single-physics simulations. Within the ANSYS Workbench
simulation paradigm, we will enable engineers to routinely
consider the effects of fully coupled physical phenomena.
High-Performance Computing
As one might expect, high-performance computing
(HPC) is a strategic enabling technology for ANSYS. The
appearance of quad-core machines on the desktop and the
increased availability of compute clusters have ushered in
a new era of parallel and distributed computing for our
customers. ANSYS has kept pace with the exponential
increase in computational horsepower with prolific development in the areas of parallel and distributed computing and
numerical methods. The result is improved scalability and
dramatically reduced run times for large-scale fluid flow,
structural and electromagnetic simulations.
Solving large-scale problems with meshes exceeding
1 billion cells has been the latest stretch goal for fluid
flow simulation. Recently, HPC and software from ANSYS
were combined to investigate the aerodynamics of a
racing yacht using 1 billion computational cells. Breaking
this barrier demonstrates our conviction for highperformance scientific computing. As computational
resources increase and engineering simulations become
larger and more complex, we will continue to ensure that
our solvers scale appropriately. Moreover, our forward
deployment of HPC technology is not limited to solvers.
The complexity of today’s models and massive amounts
of results data require more-scalable solutions for
preparing models and interpreting results as well.
ANSYS Workbench Framework
The ANSYS Workbench 2.0 platform is a powerful multidomain simulation environment that harnesses the core
physics from ANSYS; enables their interoperability; and
provides common tools for interfacing with CAD, repairing
geometry, creating meshes and post-processing results.
Instrumental to the successful integration of this unparalleled breadth of technology is a “well-architected,” open
and extendable software framework.
The ANSYS Workbench framework is designed
to provide common services for engineering simulation
www.ansys.com
applications — data management, parameterization, scripting
and graphics, among others. Release 12.0 relies heavily on
the framework’s data management and parameterization
services to integrate existing applications into the ANSYS
Workbench environment, where they have become highly
interoperable. Over subsequent releases, these applications
will leverage the framework’s graphical toolkit to establish a
consistent user interface and further blend the various
applications integrated into the platform. At the onset of
developing ANSYS Workbench 2.0, we identified scripting
and journaling as fundamental requirements of the new
architecture. As such, a top-level scripting engine has been
thoughtfully designed and lays the groundwork for future
ANSYS Workbench customization and batch processing.
Looking beyond release 12.0, all these services will be
further refined and will fuel rapid add-in development and
a further expansion of capabilities. Over time, ANSYS
customers and partners will leverage the framework’s
open architecture, enlisting its services to create tailored
applications, and will elevate ANSYS Workbench as
an application development platform for the engineering
simulation community.
Simulation Process and Data Management
ANSYS Workbench 2.0 is an environment in which a
single analyst creates and executes one or more steps of an
engineering simulation workflow. ANSYS Engineering
Knowledge Manager (EKM) extends ANSYS Workbench by
providing the tools to manage the work of a group of
analysts and myriad simulation workflows. This includes
system-level services to manage and foster collaboration
on thousands of models, terabytes of results, hundreds of
defined processes and huge investments in simulation.
Looking forward, ANSYS believes that managing data
and processes will become integral with engineering simulation. Ten years ago, simulation comprised three discrete
and sequential phases: pre-processing, solving and postprocessing. With the evolution of ANSYS Workbench, we
now look at engineering simulation as a continuous
workflow intertwining these steps. In the same way,
process and data management will become intertwined
ANSYS Advantage • Volume III, Issue 1, 2009
29
As mechanical and electrical engineering worlds converge, the combination of ANSYS and Ansoft technologies will allow engineers to analyze the behavior of combined systems.
with simulation, expanding its role and aligning it with
business processes such as product lifecycle and supply
chain management.
Electromechanical System Simulation
The ANSYS acquisition of Ansoft anticipates a trend in
the realm of engineering and design: The mechanical, electrical and software engineering worlds will rapidly converge.
Several years ago, the synchronization of these worlds
was coined “mechatronics,” and, today, the combined
disciplines are responsible for engineering the electromechanical systems found in everything from washing
machines to airplanes. A simple examination of the automotive industry reveals that the more recent and exciting
advancements have relied on mechatronics. So, at a time
when greeting cards and tennis shoes contain microprocessors and sensors, mechatronics is not just for
high-end cars and appliances; rather it is the key to
unleashing innovation in every industry.
For many years, electrical and mechanical engineering
teams have increasingly relied on simulation to accelerate
innovation, but each camp has adopted simulation tools
that were not fully capable of addressing the needs of the
other — until now. As the separation between the electronic
and mechanical worlds becomes increasingly blurred,
ANSYS has extended its range of simulation technology
by incorporating Ansoft’s world-class product portfolio.
Standardizing on ANSYS Workbench for Simulation Driven
Product Development means establishing a common
platform on which to further develop both mechanical and
electronic components and analyze the behavior of the
combined systems. Driving innovation with mechatronics
will require a comprehensive electromechanical simulation
environment developed by a leader in both mechanical and
electronic simulation software.
The Future Begins Now
With its advancements in individual physics, highperformance computing, multidomain simulation, meshing,
and key enabling technologies such as simulation workflow
and data management, release 12.0 clearly delivers on the
ANSYS vision for Simulation Driven Product Development.
But even though we have come a long way with the advent
of ANSYS 12.0, there is still an exciting journey ahead.
Standing on the strong foundation of all that ANSYS has
learned and developed in almost 40 years of leadership in
engineering simulation, we see many new opportunities on
the horizon that will extend the reach of how customers use
our technology. The ANSYS vision and strategy continue to
set our bearings, and we continue to invest in pioneering
new frontiers of the industry. And most important is that we
remain committed to enabling customers to use simulation
to develop innovative products that perform better, cost
less and are brought to market faster. ■
This article was written through contributions from Todd McDevitt
of ANSYS, Inc.
30
ANSYS Advantage • Volume III, Issue 1, 2009
www.ansys.com
© iStockphoto.com/weicheltfilm, © iStockphoto.com/meduedik
12.0: FUTURE DIRECTIONS
AUTOMOTIVE
Predicting 3-D Fatigue
Cracks without a
Crystal Ball
ANSYS tools quickly predict 3-D
thermomechanical fatigue cracking
in turbocharger components.
By Shailendra Bist, Senior Engineer, and Ragupathy Kannusamy,
Principal Engineer, Structures and Fatigue Group,
Honeywell Turbo Technologies, California, U.S.A.
Turbochargers increase the power
and boost the fuel efficiency of internal
combustion engines, but engineering
teams find they pose unique design
challenges. For example, because the
turbine is driven by the engine’s own
hot exhaust gases, components must
withstand widely varying thermal
stresses as temperatures cycle
between 120 and 1,050 degrees Celsius
for engine speed variations relating to
idle, acceleration and braking.
In particular, components such as
the cast-iron housing that directs hot
gases into the turbine are subject to
thermomechanical fatigue cracking —
a problem that often is not discovered
until parts fail in qualification tests. To
replicate four to five years of severe
thermal shock loading — far greater
than parts would experience in normal
operation — engineers perform rounds
of tests that each can be very expensive and take weeks to complete.
Several of these rounds generally must
be performed before arriving at a workable design that passes scrutiny. Many
stress intensity factor formulas are
available in handbooks for predicting
fatigue crack growth with simplified 2-D
geometries; typically, though, these
formulas are not applicable for
complex part geometries under elastic–
plastic conditions in high-temperature
www.ansys.com
environments
with multi-axial
loading. As a result,
many part designs
are based on modifying
previous geometries, trialand-error testing cycles and, in
many cases, “crystal ball” best-guess
predictions based partly on conjecture
and simplified assumptions.
Honeywell Turbo Technologies
overcomes these limitations by using
ANSYS Mechanical software together
with the ANSYS Parametric Design
Language (APDL) scripting tool to
calculate the probability of a crack
initiating as well as its most likely
growth rate, length and 3-D path.
Predicting crack fractures in this manner at the early stages of component
development enables engineers to
optimize designs upfront and help
avoid qualification test failures.
Conversely, the analysis gives engineers information on the presence of
small benign cracks that do not lead to
loss of component functionality (for
example, gas leakage or turbine wheel
rub) and can, therefore, be ignored.
For this application, J-integral
analysis capabilities in ANSYS 12.0
provide a robust solution to predict
crack behavior at high temperatures.
The J-integral is a path-independent
Honeywell Turbo Technologies produces
nearly 9 million turbochargers annually for
the automotive industry. Because turbochargers
undergo wide thermal swings, they are subject
to thermomechanical fatigue cracking.
fracture mechanics parameter that
calculates energy release rate and
intensity of deformation at the crack
front for linear and nonlinear material
behaviors. The J-integral approach
generally works best with hexahedral
meshes for the highest possible
accuracy. But representing the entire
structure with a hex mesh is a
tremendous drain on computational
resources. So in this case, Honeywell
Turbo engineers used two separate
meshing techniques: hexahedral
elements for representing the instantaneous crack front (a cylindrical volume
around the crack front called the crack
tube) and tetrahedral elements for the
remaining part volume.
Connectivity between the two
different mesh patterns is assured with
ANSYS transition elements. The size of
ANSYS Advantage • Volume III, Issue 1, 2009
31
AUTOMOTIVE
X5
X4
X3
Crack front with
virtual crack
extension
directions
X2
X1
X6
X7
X8
X9
Hexahedral elements represent the expected path of 3-D crack
propagation (called the crack tube), and less-complex tetrahedral
elements are used for the remaining volume of the part.
the 3-D crack tube depends on the
volume of the crack path’s plastic zone
and is based on the number of rings
of elements and the number of
contours to be used in calculating
J-integral values using the ANSYS
CINT command. The number of
element rings and contours should
be high enough to maintain path
independence and accuracy of energy
release rate.
In this way, ANSYS software
calculates J-integral values at each
increment of crack propagation along
several user-defined virtual crack
extension directions. The crack feature
is updated in a third-party CAD code at
each increment, then imported into
ANSYS Mechanical software where it is
The 3-D crack growth direction determining the propagation
path is based on a virtual extension direction angle in which
maximum energy is released.
meshed, solved and post-processed.
The cycle continues until a target
criterion is reached. All processes
are integrated and controlled using
in-house APDL scripts. By leveraging
improved fracture mechanics capabilities in ANSYS 12.0 for calculating
J-integrals, the method provides a
new approach to model and simulate
arbitrary 3-D crack growth and to
compute mixed mode stress intensity
factors along the crack front within the
simulation software.
This method requires calculations
to be performed iteratively for thousands of crack-growth cycles — a
prohibitively labor-intensive and timeconsuming task if performed manually
but one well-suited to the automation
Crack path
from test
result
Crack path
from test
capabilities of the APDL scripting tool.
Along with techniques such as
submodeling and load blocks for more
efficient solution processing, such
automation radically increases the
speed of performing these iterative
calculations.
Honeywell Turbo analyzed a test
case using this method to predict
growth behavior of paths in a cruciform
specimen under uniaxial and biaxial
loading. The uniaxial load case shows
prominent crack turning while the
biaxial case shows near planar growth.
The results obtained validate the
approach. The team completed further
runs to validate crack growth rates
that show promising results.
Using this automated ANSYS
fatigue crack prediction process has
the potential to increase engineering
productivity significantly, with crack
growth analysis time reduced by more
than 90 percent compared to manual
methods. This speedup has significant
value, since Honeywell Turbo engineers must analyze as many as 400
designs annually, and demands will
likely increase in the coming years as
turbochargers are implemented on a
growing number of vehicle models
around the world. In this way, technology from ANSYS is playing a critical
role in enabling the turbocharger
company to strengthen its leadership
position in this competitive industry
sector. ■
Crack path directions in cruciform specimens under uniaxial loading (top) and biaxial loading (bottom)
32
ANSYS Advantage • Volume III, Issue 1, 2009
www.ansys.com
© iStockphoto.com/ kwanisik
HEALTHCARE
Electromagnetics
in Medicine
Electromagnetic and thermal simulations
find use in medical applications.
By Martin Vogel, Senior Member of the Technical Staff, Ansoft LLC
Electromagnetic fields are used more and more in
advanced medical applications such as magnetic resonance imaging (MRI), implants and hyperthermia treatment.
As the state of the art advances, devices are becoming
more complex and simulation more indispensable in the
product design phase. With simulation, a designer can
study device functionality and address safety concerns
without exposing a patient to harm or otherwise.
In the design of an open MRI system, for example, the
details of the radio-frequency (RF) coils, a human body
model, and the large volume of the entire examination room
must all be included in an electromagnetic simulation model
to determine the resulting field accurately. The finite element
method found in HFSS (High-Frequency Structure Simulator)
software, an electromagnetic field simulation tool new to the
ANSYS portfolio, is well suited for this purpose as it uses
small mesh elements where refinement is needed and larger
mesh elements elsewhere. The human body model available
through ANSYS comprises 300 objects that, detailed down
to the millimeter, represent organs, bones and muscles.
www.ansys.com
Model of the open MRI system, which combines an
MRI model generated by Philips Healthcare with the
ANSYS human body model
Frequency-dependent electromagnetic material parameters
are also included in the model.
The RF coil design requires optimization for appropriate
image quality: The coils need to resonate at 42.6 MHz for a
1 tesla system and produce a rotating magnetic field that is
strong and smooth in the region of interest but minimizes
undesired field components. If the field varies strongly,
some parts of the image will appear to be overexposed,
while other areas will remain too dark, both of which are
detrimental for contrast. Once the specifications related to
image quality are satisfied, the designer needs to make sure
that specific absorption rate (SAR) safety regulations are
met. SAR is a measure of how much RF power is absorbed
by, and thus creates heat in, the body. When limits
are exceeded in any part of the body, the patient can
experience discomfort and tissue damage.
ANSYS Advantage • Volume III, Issue 1, 2009
33
HEALTHCARE
Sample of specific absorption rate that results on the body
when using the open MRI system, as simulated using the
HFSS electromagnetic field simulation tool
The electric field (magnitude) that results when using a receiver
implanted in epidural space in conjunction with a wireless
transmitter placed behind the back; the image shows a
horizontal cross section of the torso and arms of a person,
standing, using a wireless implant.
Model of a hyperthermia applicator and leg with tumor; in the
image, some applicator and water cooling system components
have been removed for clarity. The green object is the tumor.
Applicator design and tumor geometry provided by Duke University.
XY Plot 2
6
17W
15W
Temperatire Increase [deg C]
5
15W
10W
20W
4
Simulation
20W
3
30W
2
Measurement
1
0
0
5
10
Time [min]
15
20
Comparison of simulated and measured temperatures
in the tumor for a hyperthermia treatment case
Measured results provided by Duke University.
34
ANSYS Advantage • Volume III, Issue 1, 2009
25
Simulation results from the open MRI case indicate hot
spots under the armpits, a result that agrees with practical
experience. Analysis also indicates resonant hot spots on
the legs, even though they are not directly under the coils in
the model. Given the frequency and material parameters of
the body, the expected wavelength in the body is a little less
than 1 meter, and resonances such as these are indeed
possible. The SAR is not quite symmetric; this is expected,
as the excitations are not symmetric either. Entire scan
protocols can be simulated in the software by moving the
body automatically through the scanner.
Another medical application in which human comfort is
important is the design of wireless implants. Implants that
require directly wired power supplies can be uncomfortable
for the patient. But wireless power supplies that use
low-frequency coupling require a bulky transmitter,
reducing patient freedom. Wireless solutions that use higher
frequencies can potentially provide both comfort and freedom.
One design challenge is to transmit maximum power to the
implant while also satisfying radiation and SAR regulations.
Simulations of wireless implants provide details that
otherwise are not easily obtained for several transmitter and
receiver locations. One important finding is that, in order to
get accurate results, interior body components such as
organs, bones and fat tissue must be included in the simulation model. If not, the results can easily be off by more
than a factor two.
One final medical simulation example models an RF
phased-array applicator for hyperthermia cancer treatments. In hyperthermia, a tumor is heated with RF power
and held at an elevated temperature for some time, such as
15 minutes to 60 minutes. This weakens the tumor, which
helps to make other therapies more effective. The challenge
is to concentrate the hot spot in the tumor while minimally
affecting healthy tissue.
The applicator consists of several dipole antennas
printed on the surface of a cylindrical plastic shell that
mounts around the patient’s leg, the location of the tumor
for this case. The chosen frequency for the device,
138 MHz, is a compromise between hot spot size and
penetration depth. A higher frequency can provide a smaller
hot spot, but it would be harder to penetrate deep into
the tissue. Water cooling prevents skin heating during the
procedure and is accounted for in the simulation model.
A realistic tumor object, created using MRI data for this
patient, is inserted into the leg of the human body model.
By using the electromagnetic simulation capabilities in
HFSS software, the applicator and its settings are optimized
to focus the hot spot in the tumor. Next, the power-loss
information for every mesh element in the model is
transferred automatically to the thermal simulation
tool, ePhysics. The ePhysics product then computes
temperature distribution as a function of time, taking
www.ansys.com
HEALTHCARE
into account thermal material properties as well as water
cooling, blood perfusion, air convection and thermal radiation.
Blood perfusion refers to blood flow through capillary
vessels in muscles and organs. This flow removes excess
heat and must be included in hyperthermia simulations. To
include all the details of the capillary blood vessels would be
too complicated; therefore, a simpler model is used. It is
assumed that a certain amount of blood enters a volume of
tissue at a specified rate; it is also assumed that blood
assumes the tissue’s temperature and leaves the volume,
taking a corresponding amount of heat with it. Perfusion for
several tissue types can be found in literature [1] and is
quantified in the simulation model as a temperaturedependent negative heat source. Overall, the simulation
results proved to be very sensitive to blood perfusion.
The input power to the applicator is varied over time for
both simulation and experiment. The outer layer of the
tumor is assumed to have a higher perfusion rate than the
core, as is consistent with literature. Deviations between
simulation results and experimental data in the early stages
are likely due to the fact that initial thermal conditions in the
simulation did not exactly match those in the experiment.
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With these simulations, modeling software progresses
beyond device design into treatment planning. Finding the
proper operating conditions through simulation relieves the
patient from invasive experimental procedures. To efficiently
optimize conditions for a variety of patients in a hospital
environment, engineers must improve methods to translate
MRI scan data into personalized human body models that
are ready for simulation.
Electromagnetic and thermal simulations are well
understood and used regularly for the design of medical
equipment and procedures. The next breakthrough is
expected when personalized human body models can be
generated efficiently and doctors use simulation for
treatment planning. ■
The author wishes to acknowledge Philips Healthcare in the Netherlands
for its work on MRI and Duke University in the United States for its work
on hyperthermia.
References
[1] Erdmann, B; Lang, J; and Seebass, M. “Optimization of Temperature
Distributions for Regional Hyperthermia Based on a Nonlinear Heat
Transfer Model.” Ann. N. Y. Acad. Sci., Vol. 858, September 11, 1998,
pp. 36–46.
ANSYS Advantage • Volume III, Issue 1, 2009
35
ELECTRONICS
Fan Tray
Keeping Cool
in the Field
CAD model of the
radio chassis
A communications systems company gains millions of dollars
by using thermal simulation to bring tactical radios to market faster.
By Patrick Weber, Mechanical Engineer, Datron World Communications, Inc., California, U.S.A.
The communications systems
designed and built by Datron World
Communications, Inc. present major
thermal design challenges. The company’s radios travel with today’s war
fighters around the world in helicopters
and Humvees® as well as on foot. The
devices are designed to survive in a
wide variety of environments, ranging
from a sandstorm in the desert to a
mountain blizzard. These systems
dissipate substantial amounts of heat
yet must be sealed to the outside
environment to prevent damage to
internal components — for example,
if the radio falls into a creek, it still
must work — and to prevent electromagnetic interference.
Datron mechanical engineers face
the challenge of providing cooling
management within a completely
sealed radio cabinet in up to 60-degree
Celsius (C) ambient temperatures.
Communication systems are designed
with heat sinks external to the cabinet
that use forced-air conventional
cooling. Components with the highest
levels of power dissipation are mounted
internally near those fins. Radios contain printed circuit boards (PCBs) for
the power supply, radio frequency (RF)
filter, CPU and audio functions. These
PCBs generate substantial amounts of
heat. In addition to keeping junction
temperatures of board components
within specifications, Datron engineers
need to limit — for safety reasons —
external temperature of the heat sink
to 15 degrees C above ambient.
Historically, thermal management
design was based on engineering
experience and instinct. In order to
understand the cause of any thermal
problems, engineers had to test a wide
range of prospective solutions and
corresponding prototypes. The cost
of developing, building and testing
prototypes was high. But the resulting
delays in bringing each new product
to market were even more costly.
Datron engineers have improved the
thermal design process by using
thermal simulation.
The company now practices Simulation Driven Product Development
and begins the thermal modeling early
in the design process. Radios typically
generate 125 watts output and dissipate approximately 220 watts inside
a 15-inch wide by 15-inch deep by
5.5-inch high box. Initial models are
developed based on very limited information, such as the size of the chassis,
the RF output power and the expected
efficiency of the radio. Engineers select
primitive objects, such as cubes, as
building blocks and parametrically
assign dimensions and material
properties. Surface properties are
assigned to the outside surface of
the enclosure to represent the olive
paint that is typically used on the final
product. In the early design stages, the
Original radio design with ferrite core filters shows hot spots.
36
ANSYS Advantage • Volume III, Issue 1, 2009
www.ansys.com
ELECTRONICS
internal components are approximated
by a single component that dissipates
the total amount of heat in the radio.
As the design progresses, more
detailed information on the PCBs
becomes available. Mechanical engineers model the different PCBs and
components within the chassis and
evaluate the thermal performance.
ANSYS Icepak macros are used to
quickly generate models of standard
packages. Other macros are used to
generate heat fins from parameters
including the number of fins, fin width
and fin spacing. The design team limits
the model to approximately 1 million
cells by meshing smaller boxes around
hot spots at higher densities.
In a recent project, early models
showed that junction temperatures
exceeded the typical maximum of 125
to 150 degrees C. The original design
specified ferrite core filters that are
relatively light but have a very low
thermal conductance. Simulation using
the ANSYS Icepak tool showed that
the devices heated up the surrounding
air to the point of overheating neighboring devices. Based on this insight,
engineers replaced the ferrite filters
with aircoil filters that have a higher
thermal conductance. This design
change was the key to significantly
reducing junction temperatures of high
power-dissipation components. Once
a working design was obtained, the
engineers used parametric modeling
The Natural Convection Challenge
One of the biggest challenges Datron engineers face is simulating natural
convection. This is inherently difficult and expensive to simulate because the
buoyancy forces are constantly changing. The Datron team developed a
typical natural convection problem and compared the ability of all the
leading thermal simulation tools to solve it. Several of the software packages
took 24 hours or more, while ANSYS Icepak software solved the problem in
only 20 minutes. Datron engineers liked the nonconformal meshing tools
in the ANSYS Icepak product that make it possible to separately mesh —
usually with a finer mesh than the rest of the model — critical areas within the
system, such as high-dissipation components. Such a process increases the
accuracy in the critical areas without unnecessarily increasing computational
time requirements.
to optimize thermal management
and acoustics.
Using this approach, Datron engineers improved the performance of the
software prototype until it met thermal
requirements within the required margin
of safety. At that point, they ordered
the first thermal hardware prototype.
Testing showed that the thermal prototype closely matched the simulation
predictions and also met all of the
thermal design specifications. As a
result, no additional hardware prototypes needed to be built, and the radio
was brought to market substantially
earlier than if the company’s original
build and test method had been used.
In other recent thermal design
projects at Datron, ANSYS Icepak
simulations showed that several power
transistors exceeded the junction
temperature specification. By knowing
this early in the design process, it was
New design with aircoil filters shows that temperatures are reduced to acceptable levels.
(The filter temperatures in degrees C have gone from the 200s to the 90s.)
www.ansys.com
possible to substitute other suitable
components with lower thermal resistances. If this problem had not been
discovered until after the detailed
design process, it would have required
a considerable amount of time and
work to correct. In addition, with this
change, engineers discovered that
they could decrease the number of fins
required, which provided more room
on the rear panel of the enclosure and
made it possible to reduce the overall
size and weight of the radio.
For Datron, simulation makes it
possible to validate and optimize
designs much earlier in the development process, saving large amounts of
time and money. Engineering simulation has substantially reduced the
time required to bring new, improved
communications technology to the
marketplace, and this can translate
into millions of dollars in revenue. ■
ANSYS Icepak model shows the speed of the air from the fans along with temperature
contours on the chassis. Blue indicates cooler temperature.
ANSYS Advantage • Volume III, Issue 1, 2009
37
© iStockphoto.com/akurtz
BUILT ENVIRONMENT
Designing
Against the Wind
Simulation helps develop screen enclosures
that can better withstand hurricane-force winds.
By Steve Sincere, President, Optimization Analysis Associates, Inc., Florida, U.S.A.
One of the most popular residential structures
in Florida is the screen enclosure (or screen room),
consisting of an extruded aluminum frame covered with
screen. These structures are primarily intended to keep
debris and insects out of swimming pools and to
increase living space to include an outdoor environment.
Even so, they must be designed to resist hurricane-force
winds ranging from 100 mph inland to 150 mph in coastal
areas, depending on building code requirements.
Recent hurricanes have revealed shortcomings in these
designs. Most are developed by contractors or enclosure
fabricators based on oversimplified analytical assumptions.
Components typically are sized without regard to the
Aluminum Design Manual (ADM), Specifications and
Guidelines for Aluminum Structures as specified by
the Florida Building Code (FBC). Moreover, fasteners and
fastening methods typically are selected for ease of
fabrication or accepted convention rather than suitability for
the high wind loads.
Using ANSYS Mechanical software, Optimization
Analysis Associates, Inc. — an engineering consulting firm
specializing in mechanical analysis and design simulation —
38
ANSYS Advantage • Volume III, Issue 1, 2009
Photo courtesy Richard Graulich/The Palm Beach Post.
performed analytical studies of existing screen enclosure
designs using FBC wind loads. The company found that
the simplified methods failed to accurately calculate forces
and moments. Thus, the complex interactions among
structural members were not adequately accounted for in
the designs.
Finite element analysis (FEA) provides the most
accurate method of determining such loads and interactions. Most engineers in the screen enclosure industry
do not have a background in FEA, however, and those with
such expertise often forgo these studies due to time and
cost constraints. The answer is an automated FEA-based
screen enclosure design tool — one that is fast, is accurate
and requires no FEA skills.
A perfect platform for this task is ANSYS Parametric
Design Language (APDL) — a scripting language for
automating common analysis tasks or even building
models in terms of user-specified input variables. This adaptive software architecture enabled Optimization Analysis
Associates to create a web-based solution with a graphical
interface through which screen enclosure designs could be
conveniently specified and automatically evaluated.
www.ansys.com
BUILT ENVIRONMENT
APDL is used to automatically create, load and solve a full-frame model of a screen
enclosure from parameters entered by the user describing the structure.
Users are required to enter only minimal input data,
including basic geometry information of the frame, wind
load criteria, a sketch of the plan view (to provide x and y
coordinates for each corner), wall height, roof style, density
of structural members (number of columns to be used on a
wall, for instance) and sizes of the structural members.
From this input data, three APDL macros then automatically perform an analysis, check results against
guidelines and generate layout drawings — all completed in
less than three minutes and requiring no user intervention.
The first APDL macro reads in the data to create, load
and solve the full frame model. Beam elements represent
the structural members, which are coupled in the model
to simulate hinged or rigid connections as necessary
according to the type of connections used. Shell elements
represent the screen in a proprietary method that determines the load distribution on structural members.
Solutions are obtained for the eight wind-load cases
prescribed by the FBC.
A second macro performs all required checks defined
by ADM criteria. This complicated process begins by
accessing external files containing section properties,
material characteristics and other parameters associated
with extrusions used in the design. Then a series of
nested APDL do-loops performs the ADM
calculations for all nodes on every structural
member for each load case. The macro enters
this data into arrays and sorts through them to
determine the limiting members. The limiting
members are written to a summary report text
file, which is accessed by the web-based
interface. The report provides a simple pass/fail output
with percent overstress values (or interaction ratios).
If the user has a passing design, a third APDL macro
produces a layout drawing of the structure. This macro
takes advantage of the graphical capabilities of ANSYS
Mechanical software in generating annotation for dimensions and labels on screen enclosure 2-D layout drawings.
www.ansys.com
If the user does not have a passing design (or if the design is
too conservative), parameters may be revised and another
iteration may be performed.
Optimization Analysis Associates has written programs
for more specialized work as well. A version of the modelbuilding macro allows experienced users of software from
ANSYS to create customized structures with nontypical
shapes and/or nonstandard bracing configurations. Another
macro uses the ADM data to produce color contour plots of
interaction ratios, a calculated value of allowable stress ratio
not existing in the results file. Locations of failure to meet
the ADM criteria give a quick visual indication of problem
areas. In addition, these allowable stress ratio plots can be
animated with a modified version of the animation macro
ANCNTR.MAC and overlaid on 3-D models showing
deformed structural geometry.
One final specialized macro provides a cost estimate for
the construction of the design. This macro interrogates the
model to determine the length of each extrusion required
along with the square footage of screen and number of
fasteners, brackets, etc. It accesses an external price list file
for each item, as well as factors for items such as labor,
scrap, overhead and profit to determine the total cost. The
final output includes a complete parts list and a breakdown
of all cost components.
The automation of the modeling and simulationbased evaluation using APDL provides a fast, easy-to-use
and extremely accurate method of structural frame designs.
The screen enclosure industry now has the potential to
produce hurricane-resistant structures, to significantly
improve design productivity, and to improve cost estimating
and profit margins of contractors and fabricators who use
engineering simulation for their designs. ■
Color contour plots of interaction ratios show locations’ potential wind-force failure in red.
ANSYS Advantage • Volume III, Issue 1, 2009
39
ENVIRONMENT
Stabilizing
Nuclear Waste
Fluid simulation solidifies its role in the
radioactive waste treatment process.
Contours of solid particle concentration:
During the suction phase, the solids were
found to become more concentrated along
the bottom of the vessel, as shown by the
red color in the early suction.
By Brigette Rosendall, Principal Engineer, Bechtel National, Inc., California, U.S.A.
40
ANSYS Advantage • Volume III, Issue 1, 2009
Process Air
Process Air
Process Air
Process Air
the top to the bottom of the vessel.
This model solves a separate set of
Navier–Stokes equations for the fluid
and solid phases. It accounts for the
coupling between and within the
phases using exchange coefficients,
the most important of which is for the
fluid–solid interaction. The results made
it possible to determine whether the
mixing criteria were met under given
operating conditions.
Each vessel in the plant has a
different mixing criterion; however,
most simply require that the solids
remain in suspension and are mixed
well enough for accurate sampling and
transfer to the next step of the vitrification process. Since pulse jet mixing is
Process Air
Process Air
while keeping all mechanical components well away from radioactive
materials.
Because there had been little
previous experience with PJMs in
this mixing environment, it was critical
that the engineering team be able to
accurately predict the ability of the
units to provide sufficient mixing for
each of the different vessels in which
the wastes will be treated. Within the
waste treatment plant, each of the
mixing vessels has substantially
different geometries and processing
requirements. In addition, there is
considerable variation in the characteristics of the mixture of fluid and
particles that will be processed in the
different tanks due to separation and
concentration of the radioactive components. The mixing performance of the
PJMs is a function of the geometry of
the vessel, number of PJMs per vessel,
particle size, fluid characteristics, cycle
time and other variables. It was important to validate the ability of the PJMs
to keep the particles in suspension in
each tank.
To simulate the pulse jet mixing
process, Bechtel engineers used the
ANSYS FLUENT fluid flow simulation
package because of the software’s
unique capability depth in modeling
multiphase mixing. The Eulerian
granular multiphase model in ANSYS
FLUENT software made it possible to
predict the distribution of solids from
Process Air
Process Air
The nuclear site at Hanford,
Washington, houses approximately
60 percent of America’s radioactive
waste. Near the Columbia River, the
site stores waste in 177 underground
tanks as a combination of liquid,
sludge and slurry. A vast complex of
treatment facilities is being constructed
to convert this waste into a stable
glass-like material using a technology
known as vitrification, which involves
mixing the waste processed in these
vessels with hot glass formers such
as rutile (TiO2) or silica. The mixture
is then poured into steel canisters
and cooled to solidify for permanent
storage. One of the major challenges
in this process is keeping the solids in
the waste in suspension during its
time in the holding vessels before the
separation and processing stages.
Avoiding contact of any mechanical
components with the slurry being
mixed during holding was crucial and
led Bechtel National engineers working
on the project to select fluidic pulse jet
mixers (PJMs). The action of the PJMs
is carefully controlled by compressing
air inside them to drive the slurry into
the vessel to create the mixing action.
Only 80 percent of the slurry volume
that is suctioned up into each PJM is
expelled out of the mixers, which prevents air from escaping into the vessel.
At that point, the compressed air is
vented and a vacuum is applied to refill
the mixers. PJMs thus provide mixing
To Vent System
Pulse
Jet
Mixers
A
B
C
D
Pulse jet mixer design
www.ansys.com
ENVIRONMENT
160
140
120
Elevation (in)
a turbulent process, Bechtel engineers
chose ANSYS FLUENT software’s
k-epsilon turbulence model based on
the results of a preliminary study. In this
study, computational fluid dynamics
(CFD) specialists compared the results
of various turbulence models to
experimental data to determine which
model was best at predicting the
velocity in scaled hydrodynamics
tests.
The engineering group controlled
time-varying boundary conditions by a
user-defined function that prescribed
100
CFD
Experiment
80
60
40
20
0
0
0.02
0.04
0.06
Volume Fraction
0.08
0.1
Comparison of fluid flow predictions and experimental results for solid particle volume
fractions averaged over tank radius and mixing cycle for a 140-inch-high tank
significant compared to the cyclic variations in the concentration. At higher
elevations, there were more significant
differences between the experiment
and simulation, with the simulation
different vessel designs and to
determine whether or not PJMs could
provide adequate mixing for each configuration. The use of fluid dynamics in
this application can potentially save a
significant amount of time and money
that otherwise would be spent on
additional physical testing prior to
beginning actual waste processing. ■
See also:
Mid-suction
www.bechtel.waste2glass.com
the time-dependent velocities of each
jet and tracked the solids concentration flowing through the nozzles and at
the top of the domain. This eliminated
the need to track the free surfaces
inside the PJMs and at the fluid–air
interfaces inside the mixing vessels,
greatly simplifying the models.
The Bechtel team could perform
only very limited physical testing due to
the high cost of building and testing
the vessels and mixers. The company
commissioned the construction of
a full-scale PJM vessel to perform
experimental testing at Battelle Pacific
Northwest National Laboratory. Fluid
flow predictions of concentration and
velocity were then compared to the
measured data. The results showed that
the ANSYS FLUENT simulations slightly
underpredicted the solid-phase volume
fraction, except at the higher elevations
in the tank. This difference was not
www.ansys.com
www.hanford.gov
End-suction
predicting more uniform mixing than the
experiments demonstrated.
Even though the ANSYS FLUENT
results demonstrate slightly better
mixing than the physical experiments,
the results were close enough to give
Bechtel confidence in the ability of the
fluid flow model to provide pass–fail
judgments in rating the performances
of the PJMs. Bechtel uses ANSYS
FLUENT technology to model the many
At the end of the drive phase, higher concentrations are
predicted at the top boundary of the fluid domain while
concentrations were reduced at the bottom as the solids
were pushed away from the jet nozzle exits.
ANSYS Advantage • Volume III, Issue 1, 2009
41
OPTIMIZATION
Topology Optimization
and Casting:
A Perfect Combination
Using topology optimization and structural simulation
helps a casting company develop better products faster.
By Thorsten Schmidt, Technical Director, Heidenreich & Harbeck AG, Moelln, Germany
and Boris Lauber, Application Engineer, FE-DESIGN GmbH, Karlsruhe, Germany
Engineers usually need to ensure both functionality and
zero defects during component production. This often can
be achieved by simulating production processes and operating conditions in the virtual world. Development teams in
the machine tool industry need not only to prove the
mechanical strength of components but also to take into
account rigidity and cost.
Heidenreich & Harbeck AG in Germany was established
in 1927 as a foundry for cast iron components. Today, the
company’s range of capabilities has expanded to include
modern machine tools for finishing large, quality castings
that have high accuracy requirements. The company’s
in-house development department assists customers’
designers and develops castings of complex machine
structures according to customers’ specifications.
The comprehensive software portfolio at Heidenreich &
Harbeck contains several 3-D CAD tools, process simulation software for casting processes and numerical control
(NC) machining, a sophisticated cost calculation tool based
on 3-D CAD models, and project-planning software. In
addition, Heidenreich & Harbeck uses ANSYS Professional
software for the simulation of mechanical properties.
To provide optimal design proposals to accelerate the
development of large castings, the company obtained
TOSCA ® Structure software from German-based
FE-DESIGN GmbH. This product interfaces with ANSYS
Professional software.
In the past, the engineering team designed structural
components with primary consideration to manufacturing
restrictions. But structural analysis of these component
designs often revealed weak points, especially for parts with
a large number of load cases. Engineers then had to
perform time-consuming iterations with alternating modifications of CAD design and structural analysis in order to
fulfill customer requirements.
Currently, the Heidenreich & Harbeck development
process starts with modeling the design space, which
usually is easy to define. Engineers import the design space
geometries into ANSYS Professional software and then
generate meshes. Boundary and loading conditions are
applied. Groups of volume elements that are required for
optimization are defined in ANSYS Professional technology
as components. The engineering team exports solver input
files from the ANSYS Professional tool and imports them
directly into TOSCA Structure software with the latter’s
user interface. Using this wizard-based technology, the
optimization setup can be executed with a few mouse clicks
by re-using group definitions from ANSYS Professional to
Four Guiding
Wagons To
Be Mounted
Eccentric
Load
Model of original design,
without optimization
Design space, as provided
by customer with loading
definitions defined
Meshed, optimized structure before
including casting restrictions in the
iterative design process
Topology optimization of support arm for paper unwinder
Courtesy Bielematik.
42
ANSYS Advantage • Volume III, Issue 1, 2009
www.ansys.com
OPTIMIZATION
Structural Pre-Processing
CAD System
Generation of geometry
for design space
Optimization Pre-Processing
• FEA model
• Load cases
• Components
Optimization wizard
ANSYS Mechanical
TOSCA Structure
ANSYS Mechanical
Structural Post-Processing
Structural Pre-Processing
• Validate optimization results
• Final evaluation
FEA model of
redesigned geometry
ANSYS Mechanical
ANSYS Mechanical
Batch Optimization
Process
CAD System
Redesign using extensive
manufacturing knowledge
TOSCA Structure
Scheme of topology optimization using TOSCA Structure based on solver from ANSYS
define the design area, frozen areas, evaluation areas for
design responses, and areas for the application of manufacturing constraints. The optimization procedure is carried out
in a batch process. TOSCA Structure software iteratively
launches the ANSYS Professional solver for the analysis of
the design space model and then launches the optimization
module that evaluates results and changes material properties. Users who want to remain in the familiar ANSYS
product environment may transfer the results produced by
the TOSCA Structure product back to ANSYS Professional
for post-processing using a file containing the material
property values for the finalized optimization.
Heidenreich & Harbeck uses an optional module
from FE-DESIGN called TOSCA Smooth to convert
the optimization results into IGES or STL files containing
isosurfaces and cutting splines based on the normalized
material distribution.
For the design of castings, consideration of
manufacturing constraints plays a very important role. It is
essential to take into account demolding constraints for
parts with low-cost restrictions. For a part that is loaded by
an eccentric force leading to a torsional loading condition, a
non-restricted optimization will generate a hollow section
that would lead to high torsional rigidity. By applying a
demolding constraint in the TOSCA Structure tool, the
engineer can obtain a design proposal that is less rigid
but has no undercuts and cavities and may, therefore, be
ANSYS Professional simulation results, which
are evaluated during the optimization process
www.ansys.com
manufactured without the use of cost-intensive cores in the
sand mold. An automatic or user-defined parting plane may
be specified. For the design of stiffening ribs, the casting
constraints may be coupled with a wall thickness constraint.
A customer provided Heidenreich & Harbeck with the
design space of a support arm for a large paper roll
unwinder loaded with an eccentric force. The design with no
casting restrictions led to a hollow profile without accessibility for fastening screws. A second optimization with
casting restrictions resulted in a two-beam structure. The
final design combined the benefits of both proposals
(accessibility for screws along with hollow profile for cable
and tube-laying, which the customer added to the specifications after he became aware of the first design proposal).
Due to topology, optimization rigidity was increased by 25
percent, and weight was decreased 34 percent compared
with the former two-piece design.
In another project involving a vertical lathe housing, the
customer delivered two-dimensional sketches with the
expectation of final pattern drawings within only three
weeks. Using TOSCA Structure software, the rigidity
requirements were fulfilled with minimal material consumption, and time-consuming design iterations were avoided.
This reduced development lead time by approximately
50 percent. ■
Visit www.huhag.de and www.fe-design.de for further information.
Simulation of the casting process
Final component design
ANSYS Advantage • Volume III, Issue 1, 2009
43
MARINE
Fighting Fire
with Simulation
The U.K. Ministry of Defence uses engineering simulation to find
alternatives to ozone-depleting substances for fire suppression.
By Michael Edwards and Michael Smerdon, U.K. Ministry of Defence, Bristol, U.K.
Yehuda Sinai and Chris Staples, ANSYS, Inc.
Fires onboard ships are not
uncommon and pose a danger to both
crew and equipment. It is
vital to develop effective
methods to extinguish
these fires. At the same
time, international agreements such as the Montreal
Protocol on Substances that
Deplete the Ozone Layer have
been signed. These agreements
limit the use of firefighting agents
such as Halon that, though effective,
come with a high environmental price.
In order to find an alternative to Halon,
the U.K. Ministry of Defence (MOD)
completed a comprehensive research
program that looked at alternative fire
suppression technologies for use on
Royal Navy vessels. The work led to the
development of a low-pressure water
mist system, or fine water spray (FWS).
This new FWS system combines
salt water from a ship’s high-pressure
salt water (HPSW) system, which typically operates at a pressure of 7 bar,
together with a 1-percent-concentration
aqueous film-forming foam (AFFF).
As part of this program, MOD
validated and used simulation as a tool
to assess the performance of the FWS
system, with and without additive,
when fitted onboard a ship. This
analysis decreased the need for expensive fire testing for future assessments
and design of fire control measures.
The United Kingdom ANSYS office
developed a fluid dynamics model
using ANSYS CFX software, validated
it blindly against MOD’s full-scale
experiments, and demonstrated its
application to a real vessel.
44
Temperature isosurfaces and droplet trajectories before fire extinction is completed in a ship’s machinery space
Because of the complexity of the
application, the simulation involved a
large number of software models
that included existing capabilities,
existing models that required some
special functionality extended through
FORTRANTM, and some models that
were implemented entirely through
FORTRAN. The simulation models
were validated against data from a
large-scale experimental rig.
Measurements of the FWS droplet
initial conditions, in air and without fire,
were commissioned at South Bank
University (SBU), London, using highspeed photography. This provided
information at a specified, small radial
distance from the nozzle, for velocity
(predominantly radial) and mass flow
for each of a group of droplet-sized
bands, as a function of azimuth
and elevation. SBU performed
ANSYS Advantage • Volume III, Issue 1, 2009
measurements for two working fluids:
water and water with 1 percent by
volume AFFF. The university also
measured to ascertain whether the
additive affected the terminal speed
of a droplet with a given mass. The
SBU measurements were employed in
the initial conditions for the particle
transport model.
To determine how the fire becomes
extinguished, the combustion model
calculates the fuel evaporation rate
from the heat delivered to the fuel by
the fire. The model then predicts where
and how rapidly fuel vapor is burned
and heat is released exothermically. As
the fire cools after spray initiation and
radiation is attenuated by the spray,
soot, and gaseous products (as well as
the foam film when that is present), the
heat returned to the pool of liquid fuel
is diminished and so is the evaporation
www.ansys.com
MARINE
rate. If the spray system is appropriately designed, then extinction is
achieved when combustion process
ceases. Fuel vapor usually vanishes a
short while after the fuel evaporation
rate falls to zero.
The MOD and ANSYS research
teams validated the fluids model by
comparing it to data from a MOD
experimental rig. The rig was large
scale with a volume of 1,080 cubic
meters. Inside the experimental rig
there were mockups of the large
equipment — diesel generator and
gas turbine enclosures typically found
within a Royal Navy (RN) machinery
space. The FWS comprised 16 GW
LoFLowTM K15 nozzles fixed on a
3-meter grid near the ceiling. Buckets
at the floor were used to measure
cumulative water delivery. Additional
instrumentation was added to the
space to enable validation of the
model. Liquid fuel (F-76, which is a
common fuel for shipboard diesels,
gas turbines) was provided in one of
two rectangular trays, having areas of
Droplet trajectories and maps of water vapor mole
fraction after spray inception
Simulation model of the rig geometry and temperature
isosurfaces before spray inception
3 and 1.5 square meters, respectively.
The teams validated the simulation
against two separate tests: water
spray for the larger tray and water
spray with additive for the smaller tray.
The results of the validation were
generally encouraging, and the predicted extinction times and method of
extinguishment were reasonably predicted. There were some noticeable
discrepancies, and there was evidence
that building leakage (the effects of
which had been studied in previous
research by ANSYS) was an important
factor in this regard. Other influences
on the results of the model were identified: The fuel model used heptane
rather than F-76; the coefficient of
restitution was set at zero for water
droplets so that when they hit structures they were removed from the
model; and positioning of the mockup
structures, fuel trays and nozzle positions represented a worst case.
Engineering Simulation for the Built Environment
The technology from ANSYS that can be applied to
fire propagation, fire suppression and smoke management for ships, airplanes, trains, cars and trucks is also
used for ventilation and thermal modeling in the built
environment industry. These comprehensive multiphysics capabilities, which address safety and comfort
concerns, are frequently used upfront during the design
and construction of buildings.
In order to provide information for design improvement, design optimization and energy efficiency in the
built environment, predicting conditions such as air
velocity, temperature, relative humidity, thermal radiation
and contaminants is extremely important. The simulation
must also take into account ventilation, heat loss and
solar radiation effects on the structure walls, roof, floors,
windows and doors, as well as the presence and activity
of people and equipment in these areas. Simple air flow
modeling assists engineers and architects in quantifying
and simulating the impact of structural and equipment
design modifications on the thermal comfort of a space’s
occupants.
Engineering solutions from ANSYS provide a costeffective and accurate means of designing efficient
smoke management and detection systems. The unparalleled breadth of solutions across multiple disciplines
provides the ability to quantify the behavior of materials
subjected to fires or extreme heat and possible structural
www.ansys.com
Courtesy SOLVAY S.A.
deterioration during catastrophic events. These can
be analyzed in detail using explicit dynamics and
structural modeling. Solutions from ANSYS allow for
the analysis of events ranging from explosions that
encompass blast waves (in the context of homeland
security) to deflagrations in combustible mixtures.
— Thierry Marchal
Industry Marketing Director
Materials and Consumer Care, ANSYS, Inc.
For more information, visit www.ansys.com/industries/hvac.
ANSYS Advantage • Volume III, Issue 1, 2009
45
MARINE
Descriptions of Models Used in the Simulation
Model
Implementation
Purpose
RANS turbulence modeling (SST)
Existing model
Determines turbulent transport
Laminar flamelet
combustion modeling (Peters)
Extended
current model
To include combustion modeling of
heptane fuel and evaporated water
vapor, with reduced set of species
Soot modeling (Fairweather et al.)
Implemented
new model
Assesses impact of soot on infrared
radiation and visibility
Transient Lagrangian particle
transport model
Existing model
Assesses the impact of water spray
on fire and fuel, with two-way
coupling of mass, momentum,
convective heat and radiant heat
Multiple droplet size groups
Existing model
Determines penetration since larger
drops are better at penetrating key
regions directly, small droplets
evaporate quickly and can reach
key regions by entrainment
Coupled fuel evaporation
Implemented
new model
Calculates fuel burning rate
Subgrid droplet–congestion
interactions
Implemented
new model
Estimates direct removal rate of
droplets by subgrid congestion
Soot scavenging by water droplets
Implemented
new model
Determines how scavenging affects
infrared radiation and visibility; also
predicts delivery of scavenged
substances to boundaries
Additive effects on water spray
and fuel evaporation rate
46
Implemented
new model
ANSYS Advantage • Volume III, Issue 1, 2009
After completion of the validation,
the model was successfully applied to
a real machinery space aboard an RN
ship. MOD is proposing the use of
FWS in its future vessels for fire suppression that was validated by the
experiment [2] and this work. ■
References
[1] Sinai, Y., Staples, C., Edwards, M., Smerdon,
M., “CFD Modelling of Fire Suppression by
Water Mist with CFX Software,” Proc.
Interflam 2007, Vol. 1, 2007, pp. 323–333.
[2] Hooper, A., Edwards, M., Glockling, J.,
“Development of Low Pressure Fine Water
Spray for the Royal Navy: Results of Full
Scale Tests,” Proc. Halon Options Technical
Working Conference, 2004.
Acknowledgments
Predicts attenuation of radiant heat
arriving at pool surface
This work was a team effort. The authors wish
to thank Dr. J. Glockling of the Fire Protection
Association, Dr. G. Davies and Prof. P. Nolan of
South Bank University, as well as P. Guilbert, P.
Stopford, H. Forkel and P. Everitt of ANSYS, Inc.
for their contributions.
© British Crown Copyright 2009/MOD.
Published with the permission of the Controller
of Her Britannic Majesty’s Stationery Office.
www.ansys.com
TIPS AND TRICKS
Reusing Legacy Meshes
ANSYS tools enable users to work with
finite element models in various formats
for performing simulations as well as
making changes to part geometry.
By Sébastien Galtier, Software Developer and Pierre Thieffry,
Product Manager, ANSYS, Inc.
When designs from past projects must be analyzed, or when a
modified version of the geometry must be evaluated, the starting point
is generally the original CAD model. In some cases, however, only
legacy finite element models are available that cannot be imported
directly into the user’s current simulation software. These include
NASTRAN®, ABAQUS® and ANSYS FLUENT models, for example,
as well as many text-based archival versions of ANSYS
models. Fortunately, tools in the ANSYS Workbench environment
have been developed so users can easily convert these models
for use in creating new simulation models of the original
design and also in modifying the original shape to meet new design
requirements.
Legacy models such as the mesh for a connecting
rod, shown in Figure 1, can be read into ANSYS FE Modeler, located
in the Toolbox section of ANSYS Workbench version 12.0.
Once imported, the model is handled by the Skin Detection tool in
FE Modeler to provide a proper segmentation of the model’s facets.
The quality of the segmentation is key to the process — especially
when modifying the shape of the model — and the procedure
consists of grouping the external faces of finite elements so they
accurately represent faces similar to a geometric model. Edges and
vertices of the model will then be naturally derived from these faces.
Several methods can be used to identify the faces: detection by
angles (between the normal orientations of neighbor elements),
detection by curvatures, or employment of facet groups defined by
the user. This last method helps in creating specific areas in which
loads and boundary conditions can be applied. Figure 2 shows the
resulting geometry generated based on curvature detection in
FE Modeler from the legacy mesh. A mechanical simulation system
from ANSYS then can be linked to FE Modeler to apply loads and
boundary conditions, as shown in Figure 3, and the model then can
be solved to determine the resulting stresses and deflection (Figure 4).
After such an analysis, the model may need to be
modified because the existing design does not meet current technical
requirements. For this purpose, FE Modeler provides capabilities to
modify the geometry through a feature called the ANSYS Mesh
Morpher. A so-called target configuration is created by duplicating the
initial geometry. Then transformations such as offsets, translations or
rotations can be applied to the geometric entities. Figure 5 shows how
offsets can be used to enlarge or shrink the holes.
Once the geometry has been modified, ANSYS Mesh Morpher will
transform the initial mesh to conform to the target configuration.
These transformations are parametric, with each geometric feature
www.ansys.com
Figure 1. NASTRAN finite element
model of a connecting rod
Figure 2. Geometry created from
segmentation based on curvature
detection
Figure 3. Loads and boundary conditions
applied for analysis with mechanical
simulation software from ANSYS
Figure 4. Total deformation results from
the analysis
Figure 5. Deformed geometry, in
which the hole on the left has gotten
smaller while the other two have
been enlarged
ANSYS Advantage • Volume III, Issue 1, 2009
47
TIPS AND TRICKS
Figure 6. Raw result of conversion in Parasolid
format, with all faces NURBS representations
Figure 7. New design after sewing all faces together and
modifying geometry with ANSYS DesignModeler software
48
ANSYS Advantage • Volume III, Issue 1, 2009
affected by a parameter that is used as a way to control the
amount of morphing between the initial and target configurations. Changing the shape of an existing member can be
achieved with projection to a new CAD shape. In this case,
the faces or edges created by the skin detection process
are projected onto an imported CAD model.
It is important to note that mesh morphing modifies only
the node coordinates, and no remeshing occurs during the
process. Once the mesh has been morphed, the model can
be used in the mechanical simulation exactly as it was
done with the original model. Since the geometry topology
remains the same, all loads and boundary conditions
applied to the initial model are still valid, so the analysis
can proceed as before.
In this example, changes to the model geometry did not
affect the general shape of the model too heavily: No holes
were added, for example, and the topology remained the
same. The FE Modeler application used in conjunction with
ANSYS DesignModeler software provides all necessary
tools to allow for such changes.
To make more significant changes to the model, the
initial geometry must be converted to a Parasolid® model.
The result of the conversion is a set of surfaces
corresponding to each of the faces obtained from the Skin
Detection tool. The surfaces can then be sewn together in
FE Modeler to create volume bodies. Figure 6 shows the
raw result of this conversion, and Figure 7 illustrates
the new design after sewing all faces and modifying
the geometry with the standard features of ANSYS
DesignModeler. In this way, these tools in the ANSYS
Workbench framework allow legacy models to be reused
in a process that is not only faster but also less error-prone
than manually recreating meshes from scratch. ■
www.ansys.com
ACADEMIC
Expanding
Stent Knowledge
© iStockphoto.com/cinoby and
© iStockhpoto.com/fasloof
Simulation provides the medical industry
with a closer look at stent procedures.
By Matthew R. Hyre, Associate Professor of Mechanical Engineering, James C. Squire, Professor of Electrical Engineering,
and Raevon Pulliam, Virginia Military Institute, Virginia, U.S.A.
Heart disease, often caused by partially blocked coronary arteries, is the most common cause of death in the
world. Stenting has become one of the most popular forms
of treatment to open plaque-encrusted atherosclerotic
coronary arteries, with hundreds of thousands of such procedures performed in the United States each year. However,
according to the American Heart Association, about one in
four stent patients will experience restenosis, a repeated
narrowing of the stented artery, less than six months after
the procedure. Some patients with restenosis must undergo
a second stenting procedure to alleviate the subsequent
blockage, while for others a full bypass operation is the only
solution. A team from the Virginia Military Institute (VMI) is
combining simulation with animation software from Computational Engineering International (CEI) to help identify a
possible cause for restenosis and to find solutions that
might help reduce the risk of developing it.
The stent expansion process, with the stent shown in light gray, the balloon in dark
gray and the artery colored by arterial stress
In this image, the stent and balloon are hidden, and the remaining plot depicts only
the artery after stent inflation. The contours represent arterial stress. The red ring,
which occurs at the location of highest stress, aligns with the location at which end
flare occurs during stent inflation.
www.ansys.com
The team at VMI hypothesizes that restenosis may be
the result of arterial injury incurred during the stenting
procedure itself. During this procedure, the medical team
inserts a balloon, sheathed by the stent, into the artery and
inflates it. Once the stent expands, the balloon is deflated
and removed, leaving the stent in place.
The engineering team at VMI identified one possible
reason for injury: end flare, which is caused by balloon overhang at the end of the stent. This exerts increased pressure
on the arterial wall and may scrape it during inflation, which
could stimulate uncontrolled cell growth in that area.
The balloon’s mechanical properties vary dramatically
during the expansion process. Though it begins as a highly
flexible material, the balloon eventually expands in a nonlinear
fashion as it nears the stent’s final diameter, making the problem numerically unstable. A factor that is critical to accurately
simulating the problem is how the structure of the balloon, the
stent and the artery are meshed.
The team used HarpoonTM, from Sharc, Ltd., to generate
a complex mesh designed to follow the balloon, stent and
artery through the expansion from a 1 millimeter diameter to
a 3 millimeter diameter geometry. Once the mesh was
established, the data was exported to ANSYS Mechanical
software to provide information about stresses and
geometry changes that occur during expansion.
The team used EnSight® to turn the simulation data into
animations that depict the inflation process. The resulting
images allow the medical research team to visualize the
process for the entire assembly or to focus on the individual
components — options that are impossible during the
stenting procedure itself. By using simulation and visualization tools together, manufacturers may be able to redesign
and numerically test stent designs and procedures, arriving
at a very clear picture of how each variable affects the
overall issue — all without a patient. ■
ANSYS Advantage • Volume III, Issue 1, 2009
49
ANSYS, Inc.
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Canonsburg, PA U.S.A. 15317
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