problem for UDF velocity
 

I have a problem of numerical diffusion (I think but I'm not sure) when I postprocess an UDF for the velocity (for Vx and Vy). In fact, the angle velovity is not the same at all (on each edge) when I test it on a simple geometry like a rectangle.(putting a pressure far field on each edge)

My goal is to simulate the flow around an oscillating profile in order to test the different turbulence models on Fluent....do you think it will be better to create a dynamic mesh and make the profile move instead of the wind velocity in the boudary conditions?

Thank you very much for your time.