Wall effects

Hello,

I am simulation poiseuille flow through a channel, using zou/he bc at the inlet and outlet. I also have solid wall (BB) at top and bottom.

x = bounceback nodes
0 = inlet/outlet nodes

0XXXXXXX0
0 0
0 0
0XXXXXXX0

I do get the parabolic velocity profile but there seems to be some kind of wall effects. My velocity profile near the wall doesn’t agree with the analytic solution and i can’t figure out how to make this go away. If anyone can help me out that would be great.

Thanks,
Saurabh