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Stabilization error for two-phase flow simulation

    • abhnv_01
      I am trying to simulate a heat pipe in (3D) which has three sections:
      Evaporator - Constant heat flux (boundary conditions)
      Condensor - Constant temperature (boundary conditions)
      Adiabatic section - Zero heat flux (boundary conditions)

      I am using VOF multiphase model -> Evaporation - condensation model -> Lee model.

      Transient simulation with gravity and implicit body force formulation.

      Time step size = 0.0001 (1E-04).
      The simulation runs well for about 10-12 seconds of flow time but then it stops due to this error
      "Divergence detected in AMG solver: pressure correction        Stabilizing temperature to enhance linear solver robustness.

              Stabilizing temperature using GMRES to enhance linear solver robustness.

      Divergence detected in AMG solver: temperature
      Divergence detected in AMG solver: pressure correction"

       Even though the simulation was running well for 10-12 seconds (100,000 time steps). What can be the possible reason for this error?

    • SRP
      Ansys Employee


      This error message is an indication that equation is diverging. The most likely cause is that the under-relaxation factor (URF) for that equation is too large. Reduce the URF by 10%.

      Thank you.

    • abhnv_01

      I had already changed the URFs. 

      Following are the URFs I have kept in my case:

      Pressure - 0.5

      Density - 1

      Body forces - 1

      Momentum - 0.2

      Vaporazation of mass - 1

      Energy - 0.8

    • Rob
      Forum Moderator

      Phase change and VOF currently don't always work well. If you look at the flow field a bit before divergence what is happening? 

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