Fluids

Fluids

Incorrect pressure at outlet

    • nctrung1407
      Subscriber

      Hello,

      I want to simulate a simple 2D rectangular with transient time, VOF (air and water), and laminar - viscous model.

      I set up to pump from the top (inlet) to bottom (outlet).

      The velocity was increased from inlet to outlet, and the pressure has the same results.

      Is it incorrect? because follow Bernoulli's equation, when the velocity is increased so, the pressure is decreased.

      But in my case, it is weird.


      Does anyone solve this problem like me before?

      Please give me some advice.

      Thanks!

    • aitor.amatriain
      Subscriber
      "when the velocity is increased so, the pressure is decreased"
      This conclusion is only valid in steady flows, with constant density and negligible mass and viscous forces. I do not think that your case is well-suited to these assumptions.
      In order to help you, it would be interesting to see a general picture of the problem with the boundary conditions, as well as screenshots of the mesh and contours of some variables.
    • nctrung1407
      Subscriber
      Hello, Aitor!

      Thanks for your response!
      In my case, the fluid is changed from laminar flow to transition flow
      Please see the below figures!
      Thanks! Have a nice day!



    • DrAmine
      Ansys Employee
      Looks after bad convergence with wrong setup or set of bcs. Details?
    • nctrung1407
      Subscriber
      Sure, DrAmine!
      Which information do you want to see?
      Thanks!
    • DrAmine
      Ansys Employee
      Models used and velocity vectors.
    • DrAmine
      Ansys Employee
      + Residual Convergence

    • nctrung1407
      Subscriber
      Multiphase model and viscous model
      Residual Convergence

      Velocity vector




    • DrAmine
      Ansys Employee
      What is the secondary phase boundary condition at you velocity inlet? From Velocity vector one clearly see how the jet is deviated and the presence of some "recirculation" zones which are affecting the orientation of the jet. I assume that is only a snapshot and the orientation / flow regime is changing over the time. In this kind of cases I never trust 2D runs and tend to directly use 3D and extend the geometry downwards using a sort of venturi diffusor or plenum it does depend on what you really have at the outlet.
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