Fluids

Fluids

CFX Inlet with Negative Velocities

    • UniversityofQLD
      Subscriber

      Hello everyone,

      I am trying to simulate an idealized artery in CFX (transient), which is basically just a cylinder with one inlet (boundary type: inlet; normal speed) and one outlet (boundary type: opening; relative pressure 0 Pa). The velocity inlet is defined by a Fourier series which I have plotted in Excel and attached to this thread (blue graph). The artery I am simulating is experiencing backflow at some point in the cycle characterized by negative velocity. However, when I export the velocity results at the inlet after solving or create a transient chart at a point on the inlet face (red graph attached) I do not receive negative values but positive values with the same absolute value (e.g. instead of returning -0.05 m/s at a specific timepoint, Ansys returns +0.05 m/s).

      I am a bit stumped now. Does an inlet not allow negative flow? Does CFX export/graph just absolute values for some reason? Or is there something fundamentally wrong with my simulation? Thank you for your advice!


    • DrAmine
      Ansys Employee
      Probably you need to look into the component-wise velocities and not to the magnitude which is always positive.
    • UniversityofQLD
      Subscriber
      Thank you! I exported the component-wise velocity along the axis and I am getting the correct values now.
    • DrAmine
      Ansys Employee
      Welcome!
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