Fluids

Fluids

How to assign a normal velocity component in 2D analysis?

    • Khaled_Mohamad
      Subscriber

      Hi Every one

      I am doing multiphase flow for air and wastewater such that waste water is dragging air inside a pipe

      For model simplicity, I am trying to do a 2D analysis using Ansys fluent such that I am doing a 2D analysis for a half pipe as shown in the figure such that the flow is perpendicular to the surface

      And since it is assumed steady and fully-developed flow I want to assign a normal velocity component to the horizontal line representing some water drag and the curved surface will represent pipe wall


      But how to assign a velocity component different to the analysis dimensions itself?

      Because i found that X and Y velocity are open for edit in the boundary conditions however i want to assign a Z direction Velocity


      For more follow up there is a paper had done something similar but using a built up code instead of Ansys Fluent

    • Nikhil Narale
      Ansys Employee
      Hello,

      For your requirement, I believe, you might need to create an UDF, which will be quite a complex approach. For 2D, boundary conditions can be assigned to the edges (which acts as a boundary zones in 2d) and not to the surfaces/faces (which acts as a cell zones in 2d).
      However, I would recommend considering end-to-end rectangular geometry to plot the pipe, which will be pretty straightforward.

      Nikhil
    • Khaled_Mohamad
      Subscriber
      I cannot simplify it into a rectangle because the curvature has an effect on the obtained results also i will be able to observe the effect of secondary currents
      Ok i will simulate it 3D better
      I also Want to input the velocity of the water interface as U (at any point in X direction) = UCL (((W-2*Absolute(X))/W)^(0.25) (Not just a fixed velocity)
      Where UCL is the velocity at the centerline of the pipe, W is the width of water interface X is the distance from the center line
      Such that velocity will have power 1/4 distribution and at the walls U will be equal 0
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