1. technology and computing

ANSYS CFD v16
Update Seminar
© 2015 CAE Associates
Outline

ANSYS CFD Demo
—
—
—
CFX
Fluent
Icepak

ANSYS CFX v16

ANSYS Fluent v16

ANSYS Icepak v16
www.caeai.com
2
CFX, Fluent, Icepak demo

CHT setup
—
—

Flow domain and solid parts
Automatic fluid-solid interface generation
Internal fan model
—
—
Detail 3D fan blade geometry not modeled
Pressure jump condition
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3
Flow domain and solid parts
heat sink
fan
transformer
flow domain
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CHT with Fan Model

CFX
—
—

Pros : Easy to use, better tree outline structure, easy to identify
parts on fluid or solid side, GUI graphics to indicate which part is
selected, auto contact detection for fluid-solid and solid-solid
interfaces, multiple units available for each input, fan curve can be
implemented
Cons : need to write a CEL to implement fan swirl angle if needed
Fluent
—
—
Pros : auto contact detection for fluid-solid and solid-solid
interfaces, fan specific boundary page, easy to implement fan
swirl angle if needed, fan curve can be implemented
Cons : all fluid-solid interfaces are lumped into boundary condition
page, takes effort to identify the parts (especially on a complex
problem)
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CHT with Fan Model

Icepak
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Outline

ANSYS CFD Demo
—
—
—
CFX
Fluent
Icepak

ANSYS CFX v16

ANSYS Fluent v16

ANSYS Icepak v16
www.caeai.com
7
HPC Performance Improvements

Background
—

Dramatic HPC scalability
advances were previously
implemented, and required
additional expert parameter
settings for activation
R16 incorporates numerous
HPC improvements and
changes, to deliver excellent
scalability ‘out-of-the-box’
Note change: coupled partitioning
is the new default in R16
• Can change convergence
behavior!
—
www.caeai.com
Default HPC scaling on a transient
water turbine simulation with 40M
nodes; benchmark in collaboration with
Voith Hydro and HLRS in Stuttgart
8
I/O: File Writing with MPICH

Background
• File writing time found to be
excessive and not scaling on
some systems  identified as
an issue with MPICH-based
MPI
• Affected Cray ES mode, Intel
MPI and Microsoft’s MS-MPI
• IBM Platform Computing MPI
not affected

R16 includes a dramatic
reduction in the file write time
with MPICH-based MPI
www.caeai.com
9
Turbulence Modeling

Background
—

Accurate CFD simulations
require accurate prediction
of turbulent flow
phenomena
New turbulence capabilities
include:
—
—
BSL-ω model
Stress-Blended Eddy
Simulation (SBES) model
(β)
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10
Reattachment Modification

Background
—
—

RANS models may produce
exaggerated separation zones,
at least when separation onset
is correctly predicted
Thought to be an inherent
limitation of RANS models
R16 includes the release of an
option for the SST model to
improve prediction of the reattachment location
—
Note: effect can be reduced with
severe mesh refinement
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Red arrows show the re-attachment
location predicted with and without the
modification on a validation test case, and
how it significantly improves agreement
with the experimentally-measured reattachment location (black arrow)
11
Improved Mass Flow Rate Specification

Background
—
—

Mass flow rate boundary
condition specified for meshed
boundary area, not for machine
Change in blade count can lead
to inconsistent specified flow
rate
R16 adds new Mass Flow
Rate Area option with “Total
for All Sectors”, allowing
machine mass flow rate to be
specified directly
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Improved Mass Flow Rate Specification
Total for All Sectors area
Mesh sector boundary area
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13
Fourier Transformation for Single Stage TRS

Background
—

Fourier Transformation Transient
Rotor/Stator (FT-TRS) method was a beta
feature in previous releases. Since its
initial beta release, it has gone through a
series of improvements, including
accuracy and speed.
In R16 FT-TRS is a released feature
—
—
FT-TRS is best used on large pitch ratio
single stage turbomachines where the use
of other pitch-change models is not
possible
FT-TRS supports simulations with
incompressible fluids in rotating machines
such as pumps
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TBR in R16.0 FT Method
● Beta: Extension to FT-TRS functionality to
handle asymmetric flow situation. Connect
rotor to 360 deg. domain
‒ Impeller in a Vaneless volute
‒ Fan in a crosswind
FT-TRS
FT-TRS
Reference
FT
Compressor offdesign
performance
• Fan in crosswind
• Boundary layer
ingestion
• Ground vortex
ingestion
• Inlet swirl distortion
Impeller in Vanless Volute
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TBR in R16.0 TT Method
● Beta: Modeling multistage compressor/turbine with
combination of TT-TRS and other interfaces (i.e. PT or Stage)
‒
Aerodynamic performance
IGV
R1
TT
‒
S1
PT
R2
TT
S2
PT
Position TT-TRS where the shock cross the interface. It will help
in obtaining correct flow rate
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16
TBR in R16.0 TT Method
● Beta: Single Sided TT-TRS (STT)
•
•
Modeling multistage compressor/turbine
STT
with combination of TT-TRS and STT-TRS
TT
TT
TT
PT
Further improvement to aerodynamic
R2
IGV
R1
performance prediction
S1
TT
STT
TT
STT
Entropy contour reconstruction
Single passage per row TT/STT model
www.caeai.com
Entropy contour
Reference full-wheel model
17
Provide Harmonic Forced Response Analysis in
MAPDL
● Background
—
R15 provided export of pressure
harmonics for Mechanical cyclic
Mode Superposition, but did not
support user specification of the
engine order to export
● CFX can now export pressure
harmonic for:
—
—
Arbitrary user-specified engine
order (EO) from blade row
interaction
Blade vibration frequency from
blade flutter analysis
www.caeai.com
18
More Accurate Meridional Averaging

Background
—

Undefined values on a polyline
could skew quantities like
meridional averages and there
were limitations with TBR data
instances
Meridional length averaging in
R16 properly handles undefined
points and works correctly with
TBR data instances
R15 (top) shows discontinuities in
meridionally-averaged pressure, much
improved in R16 (bottom)
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19
Precision Control for Auto-Annotation

Background
—

Animations of transient
with display of time could
lead to ‘jumpy’ text output,
depending on given time
value
R16 adds user control for
the number precision,
giving better and cleaner
annotation display in the
viewer
—
Applies to time value and
other numerical quantities
www.caeai.com
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Outline

ANSYS CFD Demo
—
—
—
CFX
Fluent
Icepak

ANSYS CFX v16

ANSYS Fluent v16

ANSYS Icepak v16
www.caeai.com
21
Graphical User Interface

R16 introduces a
new tree-based UI
—
—
—
Branches of the tree
provide an overview
of the case set up
New right-click
menus allow quick
access to most
commonly used
functionality
Ability to save
contour and vector
definitions
www.caeai.com
22
Workbench Integration

Background
—

Continued development
of capabilities that
extend parametric
simulation capabilities
for Fluent in Workbench
R16 fully releases ability
have to multiple
upstream mesh systems
with Fluent
www.caeai.com
23
User Interface Customization

Background
—

Many users have wanted to
user scheme and create
custom user interface
components, but little
information has been
available
New documentation for
creation of custom user
interface
—
—
Instructions on how to use
scheme to customize Fluent
Examples for adding menu
items and dialog boxes
www.caeai.com
24
Extreme Parallel Scalability

Background
—

Continuously strive to improve solution scalability and stay
ahead of the competition
R16 scales better than any other commercial CFD code
—
—
830 million cells
86% efficiency at 36k cores, 1024 cores as base
www.caeai.com
25
HPC Performance Improvements

Background
—

Many cases, particularly
unsteady moving mesh
simulations, have suffered
poor performance in parallel
Performance has been
improved for simulations that
include
—
—
Wall distance calculations
Sliding mesh
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26
Poor Mesh Numerics

Background
—

Users need to be able to
solve on efficiently
generated meshes- often
this means accepting
poorer quality cells in
some regions
Improved handling of poor
quality meshes
—
—
New cell quality-based
criteria for use of special
‘poor mesh’ numerics
Improved user controls
www.caeai.com
27
Polyhedral Conversion

Background:
—

Performance bottlenecks with
polyhedral conversion have
been a common complaint
from customers with large
cases
Improvements include
—
—
Removed parallel bottleneck
for large meshes
Improved parallel
performance of optimization
step
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Mapped Mesh Interfaces

Background
—

Robust methods are
needed to handle coupled
boundaries in complex
models
New mapped interface
option for coupled walls
between zones
—
—
Fluid-solid and fluid-fluid
Supports conjugate heat
transfer and radiation
www.caeai.com
29
Acoustics Modeling

Background
—

Cabin noise
prediction is a key
application for the
automotive industry
Expanded capabilities
include
—
—
Frequency band post
processing of sound
sources
1-way coupling to
harmonic and
response analysis in
ANSYS Mechanical
(β)
www.caeai.com
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Acoustic analysis – SAE bluff body
•
•
•
www.caeai.com
87 M tet/prism mesh
15 prism-layers
Orthogonal Quality: 0.005 (use PMN)
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Acoustics Pressure Loading in Frequency Domain
Freq. 455 Hz
Freq. 1575 Hz
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Freq. 455 Hz
Freq. 1575 Hz
32
Simulated SPL vs Experiments
3
4
9
5
10
6
11
7
12
8
13
14
Freq. res= 10.8Hz
or T=0.0925s
Welch Average
Periodogram,
50% overlap
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www.caeai.com
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CFD Analysis Information
• Startup:
• Ramping down the time-step from 1e-03s to 3e-05s for 0.35s
physical time
• Sampling:
•
•
•
•
•
•
9,200 time-steps
dt = 3e-05
Many tests: 2-4-8 iter per timesteps
T sampling = 0.2634 s
Max freq. = 16.67 kHz
Min (freq.-res.)= 3.6 Hz
• Computational Info:
• ~263h for 9,200 time-steps on 168 cores (Intel Xeon 2.93 GHz,
SLES 11 SP1, 2016 GB RAM available (~300 GB used)
www.caeai.com
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Compressible Multiphase Flows

Background
—

Solver robustness
typically a bigger issue
as physics become
more complex
New numerical
treatments
—
Improved start-up and
run-time robustness
for compressible
multiphase flows
www.caeai.com
35
Free Surface Flows (VOF)

Background
—

Broad range of free surface
flow applications – many
requests for better ease-ofuse and accuracy
VOF modeling adds a number
of enhancements in R16
—
—
—
—
—
Enhanced Usability
More intuitive set up, less
error-prone
Enhanced numerics
Modified compressive scheme
Improved interface capturing
www.caeai.com
36
Eulerian Multiphase Speed

Background
—

Long transient solution
times for multiphase
simulations
Significant speedup for
Eulerian multiphase
problems
—
Non-Iterative Transient
Advancement (NITA) is
now available for
multiphase flows
www.caeai.com
37
System Coupling Improvements

Background:
—

Extend the range of
applications that can
modeled using
system coupling
Support for porous
zones with FSI
—
—
Porous media and
porous jumps are
both supported
1 and 2-way
coupling
www.caeai.com
39
Wall Film Modeling

Background
—

LWF
—
—
—

Wide demand to expand
range of application for
wall film models
UDF for impingement
and splashing
Energy transfer from
film to wall
New film boiling model
EWF
—
Support for periodic
boundaries
www.caeai.com
40
Wall Film Validation
• Cross Flow Injection
• Primary Breakup
• Secondary Breakup
• Film Formation
• Film Splashing,
Stripping & Separation
Arienti et. Al. LES Simulations
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Arienti et. al. data and LES Simulations
41
Wall Film Validation
Comparison of wall film height
Cross-flow Velocity of Air: 82 m/s Jet Velocity: 12.7 m/s
100
90
Film Thickness (um)
80
70
60
50
40
30
LWF
20
EXPT.
10
0
0
5
10
15
20
25
30
Distance along Filmer (mm)
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42
Plotting Fluent Boundary Face Values

Background
—

Using interpolated nodal
values for contour plots may
not always sufficiently
accurately reflect boundary
values applied in Fluent
R16 allows you to choose to
use face values from Fluent in
the generation of contour plots,
to create plots that are fully
consistent with boundary
values applied in the solver
Interpolation
from Nodes
Face Values
Example of difference
on a polyhedral mesh
www.caeai.com
43
Outline

ANSYS CFD Demo
—
—
—
CFX
Fluent
Icepak

ANSYS CFX v16

ANSYS Fluent v16

ANSYS Icepak v16
www.caeai.com
44
Maxwell to Icepak Coupling
• Maxwell  Icepak
Planar transformer
• Both one way or
two way coupled
• Heat flow density q”
is accurately
mapped from
Maxwell to Icepak
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45
Cold plate & Busbar Assembly
• Natural convection with side walls & top,
bottom modeled as openings
• Heat generated in Busbar is carried away
by liquid cold plate system
Busbars
Fins
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Cold plate
46
Server - Graphics Card
• Ease of use with auto
settings of power map
thresholds
• Icepak import preview and
filter enhances workflow
with Icepak
• Icepak trace modeling
successfully validated
against explicit trace
models for simple nonstandard mcm/anf based
packages
• Explicit trace modeling for
complete BGA and PCB
not yet practical –
successful with very high
refinement of Icepak trace
modeling instead
www.caeai.com
47