Inlet/Outlet Boundary for Couette Flow


I’ve got a question about the proper boundary condition for Couette flow. The case I’m dealing with is a 2 dimensional parallel gap with the inlet on the lefthandside and the outlet on the other side, while the upper wall is allocated with a velocity (based on Zou/He). For this case the boundary conditions for inlet and outlet are pretty simple, just periodic.

But I’m not sure what to apply, when I tilt the upper wall so that the inlet’s hight is bigger than the outlet’s hight. Since I use a d2q9 grid, it leads to the case that at the left side some nodes are inlet-nodes, while the nodes on the right side (same level) are part of the moving wall.

It would be great if somebody could give me a hint.
Thanks in advance


Although I don’t exactly understand, I get the impression that you’d like to simulate a situtation in which the top and the bottom wall are inclined. To achieve this, you’ll need an off-lattice boundary condition, such as the one by Bouzidi e.a.