ANSYS CFD v15 ANSYS CFD v15

Update Seminarp

© 2014 CAE Associates

New caeai.com!

Launched September 2013 Launched September 2013

2

New on caeai.com!

Expanded Resource Library Expanded Resource Library — Over 200 (and counting!) resources available for download/viewing, including

Macros, Tech Tips & Case Studies

3

CAE Associates YouTube Channel

www youtube com/caeai www.youtube.com/caeai— Complete Library of all e-Learning Series recordings

4

Connect with CAE Associates

Connect with us on Social Media! Connect with us on Social Media!

5

Outline

Flow Domain and Meshing Examples Flow Domain and Meshing Examples

ANSYS CFX v15

ANSYS Fluent v15

6

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”

7

Flow domain – single part

not sweepablenot sweepable

8

Mesh – single part

Tetrahedrons + prisms

1.26 M elements

9

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

10

Mesh – single part, three bodies

All hexahedrons, flow through meshflow through mesh

145 K elements

11

Mesh – three parts

All hexahedrons

163 K elements

12

Heat sink

13

Heat sink flow domain

14

Heat sink

15

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

16

Outline

Flow Domain and Meshing Examples Flow Domain and Meshing Examples

ANSYS CFX v15

ANSYS Fluent v15

17

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

18

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

19

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

20

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

21

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

22

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)

23

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

24

• 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

25

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

26

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

27

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

28

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

29

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, …

30

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

31

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

32

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

33

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

34

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

35

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

36

— 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

37

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

38

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

39

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 

40

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

41

Gas turbine modeled with 20 reactors325 reactions, 53 species

Diffusion FGM example

• LES of Sandia flame D

42

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

43

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)

44

(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)

45

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.

46

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

47

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

48

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.

49