Fluids

Fluids

Divergence problem multiphase (fluidized bed)

    • despinosam
      Subscriber

      Hello,


      I am trying to simulate a fluidized bed in 3D. I have nitrogen as primary phase and glass beads as secondary phase. I have been running my simulation with 1e-3 time step size and 1.5e-4 time step size, both with 40 iterations. However, in both cases when the simulation gets to 6580 iterations I get a floating point exception as shown in the picture. I do not know how to solve this problem, I have tried re doing the simulation but keep getting the same error at the same number of iteration. To get convergence I tried what the user guide suggests that is shutting down volume fraction equation for the first time steps. I have also attatched my geometry.



      I would truly appreciate any kind of help.

    • Rob
      Ansys Employee

      Check the mesh, and also think about switching to the transient solver after a shorter period of steady state flow.   If you do the sums, have you reached the minimum fluidisation velocity, or are you heading into a bubbly bed regime? 

    • despinosam
      Subscriber

      How many iterations in steady state should I run? I've tried with 1000 but velocity residual doesn't go lower than 1e-1, also after that I run the transient case and keep getting peaks on my solution. 


      I've been using the velocity to achieve bubbly regime but after reading your message I changed it to minimun fluidization velocity. 

    • Rob
      Ansys Employee

      You need to decide why you're running the model.  Multiphase tends to be transient, so may fail steady or fail to converge depending on how transient it actually is. 

    • despinosam
      Subscriber

      I need to run it in bubbly regime. 

    • despinosam
      Subscriber

      Should I run the steady state with or without the Volume Fraction Equation?

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