Stream function along solid boundary

  1. 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 ( My lecturer however said that the stream function is constant only when it is a slip boundary. Any thoughts? Who is correct?
  2. jcsd
  3. Chestermiller

    Staff: Mentor

    Your lecturer is wrong, and what "some say" is correct. Just look at the relationship between stream function and velocity to see this. unormal=-∂ψ/∂x, where x is the coordinate along the wall.

    Look up in the literature the solutions for inviscid- and viscous flow past a sphere. In both cases, the stream function is constant on the sphere.

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