If your case is incompressible,  just add the velocity on that "node" (in fact, in LB, the grid definition is better for describe.......) like pressure. Pressure BC/IC is similar with Velocity BC/IC. If your case is compressible (and more complex), just define a pseudo-region on the node which you interested and define velocity BC/IC like define velocity BC/IC on the whole boundary of your research domain.

You can send the detail description of your problem to [email protected], and I can help you define velocity on your interested "node(s)" ^_^

Hi Bojing

When we have inlet or outlet data  ( velocity  or pressure) we calculate the rho on those boundaries and then we calculate the populations. its a straight forward to calculate those 3 unknown populations (D2Q9).

But what about corners when we only know 3 populations?

So you are saying that i just need to set velocity on that nodes, but shouldnt i calculate the proper populations on those nodes?

By the Way I am just trying to solve some simple problems like poiseuille flow and etc, so my problems are incompressible, single phase flow, and 2D.

Thanks in Advance