slip flow in microchannel

Sander Nagoo

Dear sir:

I try to simulate the compressible microchannel flow ( rectangle ). The proposed model assumes the fluid is a continuum but employs a slip velocity boundary condition on the channel wall.

slip wall bc: Uwall=Kn*(dU/dy)wall

My question is, What kind of Kn I should use, mean value of a cross section or not? Thank you for your help.

best regard

Sander Nagoo