This is my first post here. I am trying to simulate flow past a cylinder placed inside a channel. I am using the bounceback BC on the channel boundary. On the cylinder boundary, I am using the method of linear interpolation provided by Bouzidi in 2001. I would like to know if anyone has used this or other BC to simulate the sane situation. I am not getting vortex shedding which is expected.

Are you not having vortex shed after applying the bouzidi’s bounceback implementation or even before applying it?
We need more details of your model to find out why is it not working as you it is expected.

[code=“fortran”]
F_x = 0.0d0 ; F_y = 0.0d0
do y = 1 , yDim
do x = 1 , xDim
do i = 1, 8
if ((x+v(i,0)>0).and.(x+v(i,0)<xDim+1) .and. (y+v(i,1)>0) .and. (y+v(i,1)<yDim+1)) then
if ((w(y,x) == fluid) .and. (w(y+v(i,1),x+v(i,0)) == wall)) then
F_x = F_x + v(i,0)(f(y,x,i)+f(y+v(i,1),x+v(i,0),opposite(i)))
F_y = F_y + v(i,1)(f(y,x,i)+f(y+v(i,1),x+v(i,0),opposite(i)))
end if
end if
end do
end do
end do

I work with fortran, I haven't confirmed it is absolutely correct, but it works fine
Regards

I loop all over the domain searching for fluid nodes that are attached to obstacle nodes

Then I apply the momentum exchange equation, where I just sum up the f(i) from the fluid and the opposite f(i) from the obstacle that share the same link between two nodes of the domain. I sum up all these values and that’s it.

you can find the equation in many papers. eq num 15 from the paper:

Boundary forces in lattice Boltzmann: Analysis of Momentum Exchange algorithm

This is actually a good question. The MEM proposed on papers actually do not consider the momentum exchange between boundary nodes. This is IMO a good approach if you do not consider moving boundaries or elastic boundaries, I insist, this is in my opinion.

Tanmay, You can try to use paraview and to generate an output of velocity values in order to visualize the velocity profile in each time step of your simulation in “.vtk” extension. This is the technique I use but I am sure there are others.