PROLB : FROM LBM TO CFD IN INDUSTRIAL CONTEXT

C-S.FR

PROLB : FROM LBM TO

CFD IN INDUSTRIAL

CONTEXT

HATEM TOUIL, CS SI LYON

2

WHAT IS PROLB ?

Accuracy

Competitive turnaround times

Easy setup

LBPhysics (Open Module)

Free and automated post-processing

CFD software based on the Lattice-Boltzmann method

ProLB : GENESIS OF THE SOFTWARE

2005-2008: MIMOSA project,

« Méthodes Innovantes pour la modélisation des sources acoustiques »

› ADEME project involving: Renault, Alstom, SNCF, Ecole Centrale de Lyon, UPMC and Ghanta

› Evaluate LBM approach using existing commercial proprietary software

› PhD thesis of S. Marié: 3D academic code (now associate professor at CNAM Paris)

Conclusions: LBM enables to predict correctly industrial applications but the soft used had a monopoly and

was very expensive.

2008-2009: Renault-CS effort propose a software demonstrator for automotive industry requirements

2009-2013: LaBS project

« Lattice Boltzmann Solver »

› FUI8 project , involving: Renault, CS, Airbus, ENS de Lyon and UPMC.

› Other partners: Matelys et Gantha

› Multi-scale and multi-resolution CFD software development

ProLB : GENESIS OF THE SOFTWARE .

2015-2018: CLIMB project

« ComputationaL methods with Intensive Multiphysics Boltzmann solver »

› BPI project, involving: CS, Renault, Airbus, Ecole Centrale de Lyon, UPMC and AMU (owners).

Partners: Matelys, Gantha, Onera, Univ. Paris Sud, Valeo.

› HPC performance optimization of LaBS

› CS provided with the commercial license : LaBS ProLB

2018-present: Albatros/OMEGA3 project

Airbus, Safran, Cerfacs, Ecole Centrale de Lyon and AMU

5

THEY USE PROLB

40+ users 10+ users

6

LATTICE-BOLTZMANN METHOD

Benefits of Lattice-Boltzmann method:

– Accuracy

– Low numerical dissipation

– Numerical efficiency

Lattice-Boltzmann method:

Transient

Low turnaround times

High accuracy

Lattice Boltzmann Method

Particle velocity discretization (finite discrete velocity set instead of

continuous particle velocity)

Space and time discretization of the discrete-velocity Boltzmann

equation

Lattice structure used in ProLB: D3Q19

Well suited for Unsteady Flow including

noise generation / propagation

7

FASTER TIME TO SOLUTION

Surface Mesh Input file *.labs

Pre-processing Solver Post-processing

PRE-PROCESSING :

•Surface mesh Loading (186 surfaces, 2,3M triangles)

•Problem setup

2h

•SOLVER :

•Volume mesh :

•200 M cells

•Simulated physical time :

•1,4 s

•480 processors

48h

POST-PROCESSING :

•Fully automated post-processing using scripts

•Hundreds of images generated

1h

Other softwares .stl

.nas

.xdmf

.case

Example for a usual drag coefficient calculation :

8

PROLB GUI: LBPRE

Modern, user friendly Graphical User

Interface

Easy setup

Easy template creation using user

variables

Fully-scriptable

Setup 3D display Setup tree

9

PROLB SOLVER: LBSOLVER

High-fidelity, transient simulations

Competitive turnaround times

Fully automated volume mesh generation

Advanced features: Rotating mesh

Results surface mesh refinement (Optimal Surface Refinement)

Advanced automatic initialization (2 Step-Refinement)

LES (SISM) + Wall Law, DNS

Porous media model

Absorbing regions to damp wave reflections at the

boundaries of the fluid domain

Direct advanced outputs (Monitors, Root Mean Square,

Average, Y+, Min value, Max value , …)

Moving mesh

Porous medium

10

PROLB MESH

Fully automated volume mesh generation, based only on Lowest case mesh cell size

Refinement level number

Rotating domain definition

Cartesian / Octree mesh

Immersed boundary conditions

Parallel (multi-core) volume mesh

User Input

exclusion

exclusion

Refinement

exclusion

Refinement

11

PROLB MESH

Mesh example of a high-speed train

(200m)

Mesh Size Cores CPU mesh

generation time

375 420 289 nodes 768 1 hour

Locomotive representation Locomotive mesh representation

12

POST-PROCESSING

Python scripts for common automotive applications using Paraview (batch

and interactive): Aerodynamics

Aeroacoustics

Export file formats: XDMF (HDF5)

Ensight Gold (.case)

Tecplot

13

POST-PROCESSING

2D streamlines Iso Cpi + 2D streamlines Iso Cpi Projected streamlines

14

POST-PROCESSING

Surface iso Cp Velocity planes along

the vehicle

3D streamlines around the

side mirror and A pillar Pressure levels – Thirds:

80 Hz

MODELS

16

Large Eddy Simulations in LBM

Discrete velocities Boltzmann equation:

where is the BGK* collision model

Relaxation time (towards equilibrium)

LBM with Boussinesq hypothesis turbulence like models

𝜈𝑒𝑓𝑓 = 𝜈 + 𝜈𝑡𝑢𝑟𝑏 (SISM** model)

*

**

D3Q19 Lattice

17

Wall modeled Large Eddy Simulations in ProLB

Classical law of the wall for // flows

Curvature effect* ( )

*

18

Wall modeled Large Eddy Simulations in ProLB

Adverse pressure gradient effect*

Characteristic velocity:

Pressure gradient – friction velocitity /ratio:

Law of the wall*:

With

*

APPLICATIONS

20

AERODYNAMICS SIMULATION – DRAG COEFFICIENT CALCULATION

Good

accuracy

Exp.

Calculation

21

AERODYNAMICS SIMULATION – DRAG COEFFICIENT CALCULATION

Rotating mesh around the wheels

Unsteady velocity

Good accuracy

and trend

Cd.A vs Rim variation

Moving wheels setup

22

AERODYNAMICS SIMULATION – RIDE AND HANDLING CALCULATION

Fully automatic setup update from a yaw angle variable

Good

accuracy

Setup Exp.

Calculation

Iso Cpi representation

23

AERODYNAMICS SIMULATION – PANEL LOADING CALCULATION

Pressure load on the driver’s window Pressure load on the panel

Direct unsteady pressure calculation

Coupling with Abaqus and Nastran codes

ProLB CFD results Structure mesh

(Nastran or Abaqus) Projection of ProLB CFD

results on structure mesh

24

AERODYNAMICS SIMULATION – FAN CALCULATION

Rotating fan mesh

Setup Velocity field

Good accuracy

and trend

25

AERODYNAMICS SIMULATION – UNDERHOOD CALCULATION

Porous media model + Rotative Fan

Good accuracy

and trend

Underhood representation

Porous medium Underhood flow

26

AEROACOUSTICS SIMULATION – WALL PRESSURE SIMULATION

Pressure spectrums on the driver window (160 km/h)

Mirror geometries variation :

Aerodynamic fields impact

Wall pressure fluctuation impact

Version initiale Rétroviseur modifié

110

115

120

125

130

135

63 80 100

125

160

200

250

315

400

500

630

800

1000

1250

1600

2000

2500

3150

4000

5000

6300

8000

Fréquence en 1/3 octave (Hz)

dB

(re

f =

2.1

0-5

Pa

)

LaBS - BaseLaBS - Modif.Exp. - BaseExp. - Modif

27

AEROACOUSTICS SIMULATION – INNER NOISE CALCULATION

Direct access to AAC variables (unsteady pressure, Prms, …)

Coupling with Actran for solid propagation

Root Mean Square of the Pressure (Prms) Pressure levels – Thirds: 80 Hz

Mean velocity measured on the Laguna 3 driver's

window in S2A wind tunnel, with and without outside mirror.

Mean velocity calculated on the Laguna 3 driver's window

in S2A wind tunnel, with and without outside mirror.

28

AEROACOUSTICS SIMULATION – EXHAUST LINE CALCULATION

Direct access to AAC variables

(unsteady pressure, Prms, …)

Exp.

Setup

Unsteady pressure

Unsteady velocity

Power Spectral Density

29

AEROACOUSTICS – BLOWER SIMULATION

Type of simulation: Isothermal aeroacoustic simulation

Rotating mesh

Goal: Pressure and velocity calculation

Good accuracy vs exp.

Velocity field OASPL

ProLB vs exp.

Exp.

30

AEROACOUSTICS SIMULATION – HVAC

Hanning window function used

ΔXmax= 25,6 cm

ΔXmin= 2 mm

8 refinement levels

Tonal peaks observed

at 400Hz and 800 Hz

31

LAGOON DATABASE

Airbus-ONERA collaboration(2006-2010)

3 configurations with various geometries complexity

Configuration #1 (simulation with ProLB)

Aerodynamic measurements (WD F2)

PIV fields & Velocity profiles (LDV)

Static pressure distributions (Cp)

Aerodynamic measurements (WD CEPRA19)

Pressure spectrums

Near-field spectrums and directivities

32

TURBULENT EDDIES WEALTH

Lagoon simulation: ProLB 7x faster than AVBP !

33

AVERAGED AXIAL VELOCITY, Z = 0 MM

Boundary layer thickness:

Too large in COARSE

Ok in MEDIUM

Recirculation zone:

Size OK

Intensity OK

Global wake size:

Good wake width

Better wake form prediction with

LBM than classical LES code

LaBS_COARSE LaBS_MEDIUM

EXPE (PIV) LES (AVBP)

34

ROOT MEAN SQUARE OF THE AXIAL VELOCITY (Z=0)

External side shear:

Vortex size and intensity more

realistic in MEDIUM case

(X=-0,2 ; Y=0,15)

Equivalent to classical LES

code

PIV measurements not

enough accurate to be able to

compare them with CFD

results

LaBS_COARSE LaBS_MEDIUM

EXPE (PIV) LES (AVBP)

35

POWER SPECTRAL DENSITY

110

100

90

80

70

60

50

Pre

ssu

re P

SD

(d

B/H

z)

102

2 3 4 5 6 7 8 9

103

2 3 4 5 6 7 8 9

104

Frequency (Hz)

Kulite 2 AVBP Fine Mesh LABs Coarse Mesh LABs Medium Mesh

Filtre

LF

filter in

the

measu

rement

s

130

120

110

100

90

80

70

Pre

ssu

re P

SD

(d

B/H

z)

102

2 3 4 5 6 7 8 9

103

2 3 4 5 6 7 8 9

104

Frequency (Hz)

Kulite 6 AVBP Fine Mesh LABs Coarse Mesh LABs Medium Mesh

120

110

100

90

80

70

60

Pre

ssu

re P

SD

(d

B/H

z)

102

2 3 4 5 6 7 8 9

103

2 3 4 5 6 7 8 9

104

Frequency (Hz)

Kulite 13 AVBP Fine Mesh LABs Coarse Mesh LABs Medium Mesh

130

120

110

100

90

80

70

Pre

ssu

re P

SD

(d

B/H

z)

102

2 3 4 5 6 7 8 9

103

2 3 4 5 6 7 8 9

104

Frequency (Hz)

Kulite 14 AVBP Fine Mesh LABs Coarse Mesh LABs Medium Mesh

36

SNOW INGESTION SIMULATION

Coupling with SPHFlow

Snow ingestion validation

(∆(exp-sim) < 150g) : Scenic 3 :

Dacia Lodgy :

Kangoo :

Scenic 4 :

Ongoing: Soiling simulation

37

THERMAL SIMULATION (ON-GOING)

ProLB aerothermal model

TAITherm solid thermal model

Two-way coupling MPCCI platform

Siemens/Amesim thermo-hydraulic model

Two-way coupling

38

PROLB / TAITHERM / AMESIM SIMULATION OF UNDER-HOOD AND UNDERBODY THERMAL FIELDS

Around 1000 solid parts coupled between ProLB and TAITherm

Expe vs. ProLB / TAITherm / Amesim simulation of under-hood and underbody thermal

41 Tair probes

Under-hood temperature

39

BRAKE COOLING PERFORMANCE

ProLB : Rotating mesh on wheel rim and brake disk

TAItherm model

Expe vs. ProLB / TAITherm simulation of brake

disk temperature decrease

4 configurations on the Megane :

Brake disk wall heat flux Wheel temperature Time (s)

Tem

per

atu

re (°

C)

Exp.

Calculation

40

AIR CONDITIONING LOOP PERFORMANCE

Air flow and temperature at idle, motor fan ON

Expe vs. ProLB / Amesim simulation of AC condenser performance at idle for 5 vehicle configurations

Quantifying warm air

recycling

Condenser heat Blown air temperature High pressure

41

EXCHAUST JET / REAR BUMPER INTERACTIONS

Exp.

ProLB

42

EXCHAUST JET / REAR BUMPER INTERACTIONS

Exp.

ProLB

43

PROLB AUTOMOTIVE SOLUTION SYNTHESIS

* Use in production

ProLB Physics Applications

Availability Availability

Aerodynamics

Drag coefficient*

Ride & Handling*

Panel Loading*

Fan*

Underhood*

Indoor Vehicle*

Aeroacoustics

Pressure load*

Exhaust line*

Blower*

HVAC*

Thermal

Engine cooling* Coming soon

Brake cooling* Coming soon

AC * Coming soon

Exhaust line* Coming soon

Snow ingestion

Hydraulics

44

Solving of the direct equations ( f )

Solving of the adjoint equations ( f*)

Calculation of the surface gradients 𝛻𝐼0

Morphing of the surface mesh

(𝑥𝑘+1 = 𝑥𝑘 − 𝜆 𝛻𝐼0)

𝑓𝑖∗ 𝑥𝑘 − 𝑐𝑖∆𝑡, 𝑡 − ∆𝑡 = 𝑓𝑖

∗ 𝑥𝑘 , 𝑡 −1

𝜏𝑓𝑖∗ 𝑥𝑘 , 𝑡 − 𝑓𝑖

∗,𝑒𝑞𝑥𝑘 , 𝑡 −

𝜕𝐼0𝜕𝑓𝑖(𝑥𝑘0, 𝑡𝑛0)

Adjoint Lattice Boltzmann Method

𝛻𝐼0 = 𝑓𝑖∗ 𝑥𝑘 , 𝑡𝑛+1

4 𝑑′

(1 + 2𝑑)2𝑓𝑜𝑝𝑝(𝑖)𝑐𝑜𝑙𝑙 𝑥𝑘 + 𝑐𝑖 , 𝑡𝑛 − 𝑓𝑖

𝑐𝑜𝑙𝑙 𝑥𝑘 , 𝑡𝑛𝑖𝑘

Standard simulation

Adjoint solver (beta)

Mesh morphing tool (e.g. Ansa)

Gradient calculation on surface

PROLB ADJOINT SOLVER (ON-GOING WORK)

45

Primary simulation, velocity field after time averaging

Adjoint field

Standard simulation

Adjoint solver (beta)

Mesh morpher tool (e.g. Ansa)

Gradient on some surface points : comparison between ProLB adjoint calculation and finite difference calculations of various order

Cylinder after morphing (image shown : after three adjoint loop)

PROLB ADJOINT SOLVER: VALIDATION ON A CYLINDER

46

Initial shape Optimized shape

PROLB ADJOINT SOLVER: EXAMPLE ON A CAR

7% reduction of the drag force (but with no style and dimension constraints…)

Sensitivy map of the surface mesh

regarding the aerodynamic drag

47

HYDRAULICS SIMULATION

Type of simulation: Isothermal

water simulation

Objective: Velocity field

comparison

Good accuracy vs Standard

Navier-Stokes code

ProLB Standard Navier-

Stokes code

Re 154420 154420

Turbulence Model LES (SISM) RANS/ k-ε

Inlet-Outlet Delta P (Bar) 0.533 0.501

ProLB

ProLB

48

HYDRAULICS SIMULATION

Type of simulation: Isothermal water simulation

Objective: Velocity profile comparison

Reference:S. Menanteau, Thesis 2012, Etude

expérimentale et numérique des fluctuations de

température en aval d’une jonction orthogonale

d’écoulements turbulents de températures différentes.

Good accuracy vs exp.

Equal CPU time vs Standard Navier-Stokes code

Geometry representation

Averaged velocity field at

the junction of the pipe

Averaged velocity data comparison

ProLB

Standard

Navier-Stokes

code

Turbulence model LES (SISM)

+ Wall law RANS

Number of mesh

cells 12 000 000 10 000 000

CPU time (same

CPU number) 20h 16h

49

HYDRAULICS SIMULATION - NUCLEAR APPLICATION

Type of simulation: Isothermal water simulation

Objective: Volumic mass flow calculation

Plenum explicit geometry (no geometry simplification)

Good accuracy vs Standard Navier-Stokes code

Very good CPU time vs Standard Navier-Stokes code

Mesh representation

Instantanous velocity

field in the plenum

Instantanous velocity field

in the exchangers part

ProLB Standard Navier-

Stokes code

Turbulence model

LES

(SISM) +

Wall law

SAS WML

ES

Number of mesh

cells

80 000

000 80 000 000

CPU time (same

CPU number,

(simulted time:1s)

5h 50h 324h

CS GROUP 22, AVENUE GALILÉE

92350 – LE PLESSIS-ROBINSON

TÉL : 01.41.28.40.00

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