ib-lbm coding session: brief...

General comments Part 1: deformable particle (sphere/RBC) Part 2: quasi-rigid cylinder

IB-LBM coding session: brief introduction

Timm Kruger

Department of Microstructure Physics and Metal Forming40237 Dusseldorf, [email protected]

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

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


Outline

1 General comments

2 Part 1: deformable particle (sphere/RBC)

3 Part 2: quasi-rigid cylinder



Outline

1 General comments





IB-LBM coding sessions

part 1: deformable particle (sphere/RBC) in simple shear flowtank-treading/tumblinglateral migration

part 2: rigid cylinder in Poiseuille flowstreamline penetrationKarman vortex street



Model properties (1)

D2Q9 BGK lattice Boltzmann modelLadd/Guo forcingimmersed boundary method with bi-linear interpolationelastic forcing model



Model properties (2)

deformable cylinderelastic springs between neighboring nodeselastic ‘bending springs’ between neighboring linksfreely moving in space

rigid cylinder

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

fixed in space =⇒ no translation/rotation



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



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



Outline

1 General comments





Tank-treading in shear flow

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



Lateral migration in Poiseuille flow

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



Hints

compile with preprocessor command#define DEFORMABLE_CYLINDER or#define DEFORMABLE_RBC

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

zero wall velocityfinite gravityposition particle close to one wall

for tank-treadingfinite wall velocityzero gravityposition particle on centerline



Outline

1 General comments





Steady flow around cylinder

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



Karman vortex street

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



Hints

compile with preprocessor command#define RIGID_CYLINDER

large system size recommended, e.g., 300× 60 (morestable)use higher 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 centerline


ib-lbm coding session: brief...

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