Inlet B.C. of generating a homogenous flow?

David

Hi,

Some references suggest the following inlet boundary conditions could generate homogenous flow in the simulation of atmosphere boundary layer in the absence of obstructions, and the simulated boundary layer will be self-sustaining. This means the inlet and outlet profiles of velocity and turbulence kinetic energy will keep the same. B.C.: U(z)=u*ln(z/z0)/k, K=u*^2/SQRT(Cu),Epsilon(z)=u*^3/k/z, k is the von Karman¡¯s constant.Cu=0.09.

I just use this B.C., but the outlet profile of TKE varies much comparing with the inlet one.The result is not self-sustaining. My case is 2D/3D incompressible, rectangular flow field, structured mesh, Segregated solver, Standard K-Epsilon model, standard wall function, roughness wall, SIMPLEC,QUICK, 10-4. Could anyone explain why? Thanks.