Slip boundary for N.S.
 

Hey,

Does anyone know how to implement a slip (free slip) boundary condition via coefficient manipulation. The discretization equation is: a_p*u_p = a_n*u_n + a_s*u_s + a_e*u_e + a_w*u_w.

It has to work on structured mesh with pipeline structure, where the fluid flows 45 degrees on the axis.

I will be very greatful if someone could help me out!