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ANSYS CFD v15 ANSYS CFD v15
Update Seminarp
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Outline
Flow Domain and Meshing Examples Flow Domain and Meshing Examples
ANSYS CFX v15
ANSYS Fluent v15
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Flow domain
Often complex Often complex— Flow passes through complex objects
• Gaps, engineering clearances, seals, highly curved surfaces, etc.
Common approach— Try an easiest meshing method
Tetrahedron + prism elements most likely used to mesh complex parts— Tetrahedron + prism elements most likely used to mesh complex parts
Model outcome— “Isotropic” nature of tetrahedron elements leads to large, sometimes
excessive element count— Difficult to resolve thin gaps
Di ti l l t i ti— Disproportional element size ratio— Long meshing time— Sometimes WB meshing fails to handle “problematic geometry”
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Flow domain – single part
not sweepablenot sweepable
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Mesh – single part
Tetrahedrons + prisms
1.26 M elements
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Flow domain decomposition
B d t f t i l fl d i b lit i t Based on geometry feature, single flow domain can be split into many separate 3D volumes
Take advantage of available WB meshing methods, find the best method for each flow volume
— Is any flow volume sweepable ?— Can multi-zone be applied ?
Reduce overall element count— Reduced CPU time, increase throughput— Important for large problems and unsteady analysis
“Stitch” flow volumes together— “Domain Interface” in CFX— “Mesh Interface” in Fluent
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Mesh – single part, three bodies
All hexahedrons, flow through meshflow through mesh
145 K elements
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Mesh – three parts
All hexahedrons
163 K elements
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Heat sink
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Heat sink flow domain
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Heat sink
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Data comparisons
Measured data ~ 71 ˚C above ambient
ANSYS CFD /Mesh size
Center of heat sink˚C above ambient
Averaged˚C above ambient
CFX~ 0.46 M 77.81 (not converged) 76.13 (not converged)
CFX~ 1.34 M 69.94 68.09
CFX~ 3.07 M 71.63 69.14
Icepak (Fluent)~ 1.33 M 73.38 71.74
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Outline
Flow Domain and Meshing Examples Flow Domain and Meshing Examples
ANSYS CFX v15
ANSYS Fluent v15
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Parallel Scalability
HPC improvement HPC improvement Investigation of various solver
parallel scalability limitationsI d t i l b h k Industrial benchmarks
Single and multi-domain (incl. two-stage radial compressor gand six-stage axial compressor)
Steady and transientSolver wall clock speed-up on 150M
node intake caseSteady and transient
Implemented improvements accessible via expert parameterparameter
Default setting does not incorporate changes
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Industrial benchmark application
Parallel Scalability
Industrial benchmark application — 6-Stage Axial Compressor— 13m nodes, 14 Domains, 12 Mixing Planes
Courtesy Siemens AG, Mülheim, Germany, ASME IGTI Paper GT2013-94639
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Laminar to Turbulence Transition
• One-Equation• One Equation Intermittency-based Transition Modelling (β)
— Evolution of the γ-Reθmodel
• Alternative wall functionAlternative wall function calibration for omega-based models (β)
I d b h i i th— Improved behaviour in the laminar limit
• Delayed DES (DDES) y ( )model (β)
— Avoid switch to LES in boundary layer swept wing test case in which ability to
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boundary layer p g ycapture transition due to cross-flow
instability is critical
Moving and Deforming Mesh
• Improved robustnessImproved robustness— Better defaults for stiffness— Additional options— Blended stiffness (β) — Jacobian Multiplier (β)
Improved sliding mesh onExample showing mesh stiffness resulting with
old defaults (top) vs. new defaults (bottom)• Improved sliding mesh on surfaces of revolution
— More robust for radial
old defaults (top) vs. new defaults (bottom)
machines— Reduced parallel memory
overheadoverhead• Alternative model for
periodic mesh motion (β) Hydraulic runner test case : rotation by +/-5 d h d t bl h d f ti ith
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5 deg showed stable mesh deformation with default settings, with significant
improvement in R15
Eulerian Multiphase
• Numerous enhancements and extensions
Lift force for Algebraic Slip— Lift force for Algebraic Slip Model (β)
— Improved turbulent di i f l t b l tdispersion for large turbulent Stokes number (β)
— Different correlations for RPI wall boiling sub-models (β)
— Bulk adiabatic boundary condition for heat transfer atcondition for heat transfer at a wall (β) Lift forces lateral to direction of
travel can be important when dispersed phase are subject to shear
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Lagrangian Particle Tracking
N d l i d• New model options and diagnostics
— Output of model quantities forOutput of model quantities for diagnostics of primary breakup model (LISA, E-TAB,
) (β)…) (β)— Additional wall film model (β) — Limits/bound on particle
i i i d
Schematic of LISA model quantities
integration timestep and particle temperature (β)
• Additional modeling flexibilityg y— Use of particle boundary data
in CEL expressions (β)
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Animation of wall deformation based on particle erosion
Blade row analysis methods
SteadyStage/ Mixing-Plane
TransientFull-Domain
TransientFull-Domain
Transient withPitch-ChangeTransient withPitch-Change
• Single Passage per Row• Good @ DP &/or
Low blade loading• Poor @ off DP &/or high
• Accurate account for unsteady interactions
• Req. Full or Partial wheel modeling
• Accuracy of full domain
• Account of unsteady interaction• Poor @ off DP &/or high
blade loading• No account of unsteady
interaction
wheel modeling• Large comp. expense
• Memory• CPU
interaction• Reduced domain
model• low comp. expense
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• Low comp. expense
Transient Blade Row
Transient Blade Row Transformation methods minimize• Transient Blade Row Transformation methods minimize number of simulated passages, providing enormous efficiency gains and reduced infrastructure requirements
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Transient Blade Row applications
Single & multistage analysis
A i l & R di l
Inlet Disturbance
- Axial & Radial
Inlet Disturbance- Frozen Gust Analysis - Fan Inlet Distortion
Aeromechanical Analysis-Blade Flutter-Forced-Response
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Purdue compressor
Transient Blade Row example
p• Full domain 180o: 10 IGV / 9 R• TT : 1 IGV/1R
Forcing function on IGV: Integration of pressure distribution at 90% span from experiment and CFD
Off-Design PointDesign Point
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Transient Blade Row example
( )Density-Gradient
TRS 10-9 (Full Domain)Density-Gradient
Transient Blade Row
This animation is from a solution obtained on single passage per row using TT method and later reconstructed for the full geometry
This animation is from a solution obtained on the Ref. geometry using TRS method. The post processing done
i lti l t i t fil
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reconstructed for the full geometry using a single results file
using multiple transient files
Blade Flutter : Aerodynamic Damping
• Flutter occurs at blade natural frequencyq y• Dependent on aerodynamic & structural characteristic of the blade• Modal analysis natural frequency and corresponding modal shapes• Only specific mode shapes are used in specifying the blade motion in• Only specific mode shapes are used in specifying the blade motion in
CFD calculations
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CFD-Post
• Instancing and Expansion of TBR solutions for post-• Instancing and Expansion of TBR solutions for postprocessing
— Full range of plots and quantitative analysis with data i t iinstancing
— Points, lines, planes, surfaces (incl. turbo), volumes, …
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Turbomachinery speed line
• New boundary condition for across full speed line
— “Exit-corrected mass-flow outlet” applicable from deep choke to stallchoke to stall
— Avoid set-up change along speed line, ensure continuityGi d i d fl— Gives desired mass flow specification in stall region, and includes effect of
i i i h kpressure variation in choke region
Speed line for compressor test case showing
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consistency of results between new exit-corrected mass flow BC and other BCs
Outline
Flow Domain and Meshing Examples Flow Domain and Meshing Examples
ANSYS CFX v15
ANSYS Fluent v15
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Parallel Scalability
700800900
96 Million cells• High solver scalability at large core counts
200300400500600
Ratin
g
R15.0
Ideal
— ~84% efficiency for 96M cell case at 10240 coresCoupled solver LES and
0100
0 2048 4096 6144 8192 10240 12288
NumCores
Ideal— Coupled solver, LES, and species transport
— Similar trend for 111M cell t d d b h kstandard benchmark
— Segregated solver2500300035004000
g
111 Million cells
05001000150020002500
Ratin
g R13.0
R14.0
R15.0
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0 2048 4096 6144 8192 10240 12288
NumCores
Other Parallel Enhancements
I d ll l• Improved parallel error handling
— Ability to restore runningAbility to restore running simulations to a usable state after a crash
Faster solutions using GPUs• Faster solutions using GPUs— Accelerated AMG solver
performance for 3D coupled pressure-based solver cases
• Support for Intel Many-Support for Intel ManyIntegrated-Core (MIC) (β)
— Intel Xeon Phi
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Adjoint Solver
• Expanded adjoint solver capabilities• Expanded adjoint solver capabilities— Support for larger scale problems— Up to 30 millions cells— Ability to solve the adjoint equation for energy— Observables as integrals of heat flux and temperature
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Moving and Deforming Mesh
• Increased temporal accuracyIncreased temporal accuracy— 2nd order temporal
discretization with layering and re meshingre-meshing
• Improved accuracy and robustness for mesh smoothing
— Node-based solver for diffusion smoothingdiffusion smoothing
— Linearly elastic solid smoothing
• Increased flexibility with local re-meshing
Detection and re-meshing of
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— Detection and re-meshing of attached boundary layers
TurbulenceSST‐SAS
• Transition SST model with SAS and delayed DES
Increased flexibility for— Increased flexibility for modeling transitional flows
— Benefits external flows Transition‐SST‐SAS
• New WMLES S-Omega d l f l timodel formulation
— Offers improved accuracy and broader range ofand broader range of applicability
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Eulerian Multiphase
• Faster and more robust as e a d o e obusmultiphase calculations— Adaptive time-stepping
0 6
0.8
1
me Fixed timestep
• Log-normal initial particle size distribution for population balance 0 2
0.4
0.6
CPU
Tim
Fixed timestep
Adaptive time stepbalance
— Quicker set-up and more accurate approximation of
ti l i
0
0.2
particle size• New interphase heat transfer
modelsmodels — Better prediction of heat
transfer between phases
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Free Surface Modeling
• Faster VOF simulationsFaster VOF simulations— Speed-ups of 4% - 36%
over a range of cases
From Neighboring Cell
• Open channel flow enhancements
— Suppression of numericalSuppression of numerical reflection at inlet boundary
— Transient profiles for free surface and bottom level From Free Surface Levelsurface and bottom level
— Numerical beach improvements
From Free Surface Level
— Better modeling of oblique waves
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Eulerian Wall Film
• Several enhancements and extensions
C tibilit ith i— Compatibility with moving walls and MRF
— Robust implementation of splashing model
— Evaporation and condensation with Euleriancondensation with Eulerian and mixture multiphase modelsMass flux reporting at— Mass flux reporting at boundaries
Predicted wall film thickness on a NACA
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0012 airfoil verification case
Reacting Flow
• Enhanced modeling of NO mass fractionEnhanced modeling of detailed chemical mechanisms
— Species limit increased from 50 t 500
NO mass fraction
50 to 500— Dynamic mechanism
reduction — 2-10x faster speed-up
depending mechanism sizeReactor network model for
CO mass fraction
— Reactor network model for rapid 3D simulations with detailed mechanismsFGM (Fl l t G t d— FGM (Flamelet Generated Manifold) model for diffusion flames
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Gas turbine modeled with 20 reactors325 reactions, 53 species
Diffusion FGM example
• LES of Sandia flame D
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Battery Modeling
N lti l lti di i l (MSMD) b tt d l• New multi-scale, multi-dimensional (MSMD) battery model— Single battery cell or multiple cell battery pack— Fully coupled flow thermal and electrochemistryFully coupled flow, thermal and electrochemistry— Fully parallelized
Oh i h i
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Ohmic heat generation Total heat generation Temperature
Electro-Magnetics Coupling
• Improved surface mapping capabilities for coupling• Improved surface mapping capabilities for coupling between Fluent and Maxwell— Support for surface losses on interior zones— Use external data transfer for CFX
Contours of the mapped surface loss in Fluent(Above) Maxwell mapping surface panel (Right)
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(Above) Maxwell mapping surface panel (Right)
Heat Transfer and Acoustics
• Extensions for heat transferExtensions for heat transfer and radiation
— New multilayer shell d ti d lconduction model
— Surface-to-surface radiation with non-
U d fl d iconformal interface and mesh
— Anisotropic heat
Unsteady flow structures computed in simulation of generic car mirror
Anisotropic heat conduction in solids
• Improved acoustics l i
SPL for octave band centered at 63 Hz (left) and 500
analysis— Banded analysis of
acoustic sources (β)
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SPL for octave band centered at 63 Hz (left) and 500 Hz (right), showing areas of high noise generation
Fluid Structure Interaction
• Two-way coupling between Fluent and Mechanical— Surface thermal FSI
Surface thermal and structural FSI— Surface thermal and structural FSI
Two-way transfer of surface temperatures and convective film coefficients to solve for the temperature field in an exhaust manifold.
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Modeling Contact with FSI
•In Mechanical a Contact Offset can be•In Mechanical a Contact Offset can be specified
— This prevents the fluid meshing getting pinched offpinched off
— But we still need to block the flow in Fluent in some cases
•A Fluent UDF is available which:— Detects when surfaces are within a
specified tolerance
— Does not prevent further boundary motion – Mechanical should do this
— Can block the flow in the remainingCan block the flow in the remaining gap using a momentum sink approach
— Works in serial and parallel, but the contact zone must be on a single
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co tact o e ust be o a s g epartition
Icepak Enhancements
PCB object supports trace and via import PCB object supports trace and via import— Supports all ECAD formats using AnsoftLinks— Also able to select/highlight traces by net or
trace nametrace name
Mesher speed improvementsFaster meshing for models with many objects— Faster meshing for models with many objects
Coupled Pressure-Velocity solver optionAl i h d f l d l— Alternative to the default segregated solver
GPU Accelerator for Parallel Processing— Can be used to accelerate view factor
calculations and the coupled solver
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Design Modeler Electronics
Design Modeler Electronics now Design Modeler Electronics now supports the creation of:
— PCB objects from blocks or polygons• Specification of detailed or compactSpecification of detailed or compact
PCB options available once the DM model is imported into Icepak
— Enclosure objects• Enclosure can have up to six sides• For each side of the enclosure thick• For each side of the enclosure thick,
thin or open conditions can be specified.
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