how to set the BC of the backstep?

Tom

dear all 3D,subsonic,compressible,the rate is 1.5 . the inflow bc : r,u,v,w are specified,P float. the outflow bc: only p is specifyed, and equal p(infinity) up and down : no-slip wall spanwise : period

Macomark scheme(1969) is used in my code. the velocity v is not zero near up-wall of inflow , and the value is about 0.25(non-dem) why? is it 'Ossen flow'? Because i can not find the DNS results of channel flow,i have to deal with my inflow bc like that pre-mentioned. the velocity u is sepecifyed the analytical solution of Poiseuille flow ,although the code is compressible(Mach number==0.2).

would anyone give me some advices?

thanks.