General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

IB-LBM coding session: brief introduction

Timm Kruger

Department of Microstructure Physics and Metal Forming40237 Dusseldorf, Germanyt.krueger@mpie.de

LBM Workshop (Edmonton, Canada), August 22–26, 2011

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 1 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Outline

1 General comments

2 Part 1: rigid cylinder in external flow

3 Part 2: deformable cylinder in external flow

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 2 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Outline

1 General comments

2 Part 1: rigid cylinder in external flow

3 Part 2: deformable cylinder in external flow

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 3 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

IB-LBM coding sessions

part 1: rigid cylinder in external shear flow

Karman vortex streetstreamline penetration

part 2: deformable cylinder in external shear flowlateral migrationtank-treading

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 4 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Model properties (1)

D2Q9 BGK lattice Boltzmann modelLadd/Guo forcingimmersed boundary method with bi-linear interpolationforcing via constitutive model (no direct forcing)

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 5 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Model properties (2)

rigid cylinder

elastic penalty force for each node, F i ∝ −(x i − x0i )

fixed in space =⇒ no translation/rotation

deformable cylinderelastic springs between neighboring nodesfreely moving in space

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 6 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Algorithm structure

simulation initialization

specify simulation parameters (user)

allocate memory and initialize variables

simulation loop

1 compute node forces from deformation via constitutive model2 spread node forces to fluid lattice3 perform LBM including external forcing4 interpolate fluid velocity to nodes5 update node positions6 write data to disk if desired7 go back to first step

finalize simulation

return

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 7 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Algorithm structure

simulation initialization

specify simulation parameters (user)

allocate memory and initialize variables

simulation loop

1 compute node forces from deformation via constitutive model2 spread node forces to fluid lattice3 perform LBM including external forcing4 interpolate fluid velocity to nodes5 update node positions6 write data to disk if desired7 go back to first step

finalize simulation

return

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 7 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Algorithm structure

simulation initialization

specify simulation parameters (user)

allocate memory and initialize variables

simulation loop

1 compute node forces from deformation via constitutive model2 spread node forces to fluid lattice3 perform LBM including external forcing4 interpolate fluid velocity to nodes5 update node positions6 write data to disk if desired7 go back to first step

finalize simulation

return

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 7 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Remarks

code and compiler

single file, parameters hard-coded =⇒ compile after change

compiler call:g++ -O3 IBLBM_2D_example.cc -o binary

execute without parameters: ./binary

folders and files

write VTK data into folders

vtk_fluidvtk_particle

=⇒ ParaView

write ASCII data for force, position, velocity into data.dat=⇒ gnuplot, Tecplot

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 8 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Outline

1 General comments

2 Part 1: rigid cylinder in external flow

3 Part 2: deformable cylinder in external flow

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 9 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Karman vortex street

aspects to studyfind valid parameters for vortex streetidentify & investigate numerical problemsobtain lift & drag forcesvisually inspect results with ParaView

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 10 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Steady flow around cylinder

aspects to studyfind valid parameters for stready flowvisually inspect results with ParaView

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 11 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Hints

compile with preprocessor command#define RIGID_CYLINDER

large system size recommended, e.g., 300× 60 (morestable)use high particle rigidity (rigidity important)for vortex street

zero wall velocityfinite gravityposition particle close to but not on centerline

for steady flowzero wall velocityfinite gravityposition particle on centerlinee

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 12 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Outline

1 General comments

2 Part 1: rigid cylinder in external flow

3 Part 2: deformable cylinder in external flow

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 13 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Lateral migration in Poiseuille flow

aspects to studyfind valid parameters for lateral migrationobserve migration velocityvisually inspect results with ParaView

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 14 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Tank-treading in shear flow

aspects to studyfind valid parameters for tank-treadingobserve tank-treading rotation and streamlinesvisually inspect results with ParaView

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 15 / 16

General comments Part 1: rigid cylinder in external flow Part 2: deformable cylinder in external flow

Hints

compile with preprocessor command#define DEFORMABLE_CYLINDER

small system size recommended, e.g., 30× 30 (faster)use small particle rigidity (deformability important)for lateral migration

zero wall velocityfinite gravityposition particle close to one wall

for tank-treadingfinite wall velocityzero gravityposition particle on centerline

Max-Planck-Institut fur Eisenforschung, Dusseldorf, Germany IB-LBM coding session 16 / 16