Hi, I am studying fluid mechanics and I am trying to get to grips with slip and no-slip boundaries. I know that: Slip ---> Occurs when fluid is inviscid so no viscous stress at boundary. No-slip ---> Viscous effects mean the the tangential velocity must be zero, relative to the boundary. Also, for both slip and no-slip boundary conditions you have no normal flow if the boundary is solid and impermeable. However, the problem I have is that some say that if you have the no normal flow condition, then the stream function is constant regardless of whether it is a slip/no-slip boundary (http://scicomp.stackexchange.com/qu...non-symmetric-obstacle-using-stream-functions). My lecturer however said that the stream function is constant only when it is a slip boundary. Any thoughts? Who is correct?