Hi folks,
I am trying to set up a LB-simulation to simulate a pipe flow and I am experiencing several problems. I hope, you can help me in an understandable (not heavy formula using) way.
First and most important question set:
What should I do with any walls? I understand there are a lot of different approaches (bouncing back, inamuro, free slip, no slip, complex things, …) - but I fail programming any of these. As far as I understand, for a simple pipe flow I need a bouncing back condition.
Is this still right?
If so, all I have to do is to take the distribution functions pointing towards the wall (e.g. pointing North, Northeast, Northwest) and put them into the wall (South, Southeast, Southwest). [This ought to be free slip or what it is called.] Now, if I switch east and west I should have no-slip.
Is this still right?
And then, what do I do if an obstacle is to be simulated? There could be corners of which I have absolutely no clue what to do with them.
To the not critical questions:
Is there any way to set boundary conditions by defining macroscopic parameters (e.g. von Neumann, Dirichlet)?
Is there a way, to realize different viscosities? I think, viscosity is only used in the collision, but can I just use different (and chaning) viscosities in a single cell (and keep conservation of mass)?
Many thanks for your time and answers.