I try to solve 2D channel flow. But I have some problems. Before explaining the problems, I mention my settings.
I use D2Q9 lattice. Also I use LBGK.
I use one way bounce back scheme. (on north and south walls)
For example south boundary
- I give velocity BC at west domain with Zou-He scheme. Al so I give fully developed velocity profile.
- As a outlet BC, I give zero gradient velocity (first order)
- For calculating the equilibrium distribution function,
- My process sequence is;
As a initial calculate feq for initial condition, and f=feq,
And iterations begin. Collision step, streaming step, BC (velocity, bounce back and outflow), calculatong rho, u and v for new iteration.
My problem is, although flow is fully developed, veloctity is decreased from that I gave. Also density is decreased. So I lose mass.
How can I solve this problem? Please help me