Fluids

Fluids

non-zero boundary condition on the wall

    • Mr Eri MM
      Subscriber
      Hello everyone,
       
      I have a problem with flow between fixed parallel plates. On the top plate I have a no-slip condition. But on the bottom plate, I have a boundary condition where the velocity is non-zero. How can I add the boundary condition on the bottom plate? Would it be through a UDF? Looking through Fluent, I couldn't see an option in the wall tab.
    • eric1234598765
      Subscriber

      Hi,

      What's the boudnary type of the bottom plate? If it is a interface, then choosing couple option in the mesh interface setting in Fluent could treat that boudnary as impermeable wall.

      Otherwise, it is strange that Fluent can not set a no slip condition on a wall boudnary.

      Eric

    • DrAmine
      Ansys Employee

      On the bottom wall: what do you know? Do you know the velocity of the wall? Does the fuild stick to that moving wall?

    • Mr Eri MM
      Subscriber

      Hello Eric and DrAmine.

      In fact, it’s like the bottom plate has some holes where the fluid enters and leaves with a certain velocity defined by a boundary condition: (du/dy = alpha/ sqrt(k)) * (ui – um). That is, I need to set this condition exactly on the bottom wall.

      Note that if this problem were to be solved analytically, I would have two boundary conditions.

      (1) When y = 0 ==> du/dy = alpha/ sqrt(k)) * (ui – um)
      (2) When y = h ==> u = 0

      For the top plate the boundary condition it’s just a no-slip condition that can be set easily by fluent. But on the bottom plate I would need to put the equation: du/dy = alpha/ sqrt(k)) * (ui – um).

      In short, what I really need to know how I can put an equation as a boundary condition on the bottom plate.

      !Note that the plates are fixed.

       

    • DrAmine
      Ansys Employee

      Your BC looks after providing a shear stress to the Wall BC. You can explore that.

    • Mr Eri MM
      Subscriber

      Ok DrAmine, thank you.

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