Adverse Pressure Gradient using Fluent
 

This is my first experience with using Fluent and I'm already having some troubles. I'm trying to set up conditions for Couette flow, but it seems to be harder than it appears. For just a rectangular grid, my boundary conditions are a wall at the bottom, pressure outlet on the right (guage pressure=0), moving wall at the top, and velocity inlet on the left, which I imported a linear profile. My flow is incompressible. For some reason, I'm getting an adverse pressure gradient in the very top left hand corner which is giving me incorrect data. Any ideas of how to get rid of this pressure gradient?

does your velocity inlet boundary condition match the velocity you apply for the upper wall? anyway, i would suggest a pressure boundary condition instead of the velocity inlet...

I tried the pressure inlet boundary condition, but the results didn't match the theoretical data that I'm comparing my work to. I'm currently studying incompressible flow over a sublayer fence and according to the data separation should occur in front of and behind the step, forming little eddies. My main area of interest is the viscous sublayer of the boundary layer so I'm dealing with a very small area. I want to find the pressure difference in front and behind, but with this adverse pressure gradient, my results aren't turning out the way they should.

I've also checked my velocity on the top with the velocity profile and I don't think that's the problem