Hello everybody;

I applied the periodic for my inlet and outlet (z direction), and free slip condition for four walls.

Box3D inlet(0,nx-1,0,ny-1,0,0), outlet(0,nx-1,0,ny-1,nz-1,nz-1);

Box3D wall1 (0,nx-1,0,0,0,nz-1) , wall2 (0,0,0,ny-1,0,nz-1) , wall3 (nx-1,nx-1,0,ny-1,0,nz-1), wall4 (0,nx-1,ny-1,ny-1,0,nz-1);

boundaryCondition.setVelocityConditionOnBlockBoundaries (

lattice, wall1, boundary::freeslip );

boundaryCondition.setVelocityConditionOnBlockBoundaries (

lattice, wall2, boundary::freeslip );

boundaryCondition.setVelocityConditionOnBlockBoundaries (

lattice, wall3, boundary::freeslip );

boundaryCondition.setVelocityConditionOnBlockBoundaries (

lattice, wall4, boundary::freeslip );

But by some reasons, the velocity of at wall 3 and wall 4 are much higher than wall 1 and 2. The picture below is the velocity from wall 1 (x= 0) to wall 3 (x= 0.0064)

I expected the velocity at x=0 and x = 0.0064 should be similar.

I looked at the example code in Palabos, for example, ExternalFlowArondObstacle, sometime they use ny-1, and sometime they use ny-2; so I am not sure how the thickness of the wall where you apply the boundary condition will affect the result ? My wall now is 0 thickness cell, should I change it to 1 thickness cell ?

Thank you