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Global courant number exceeds 250 for constant heat flux bcs.

    • abhnv_01

      I am trying to simulate a heat pipe in (2D) which has three sections:

      1. Evaporator - Constant heat flux (boundary conditions)
      2. Condensor - Constant temperature (boundary conditions)
      3. 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 works well for first 10000 time steps (1 seconds of flow time) and then this error where global courant number exceeds 250


      But here is a mystery, the simulation runs well with constant temperature boundary condition at the evaporator.


      I want results with constatn heat flux, I am not able to track the error, any help will be highly appreciated. 

    • SRP
      Ansys Employee


      I suggest to try variable time stepping in order to automatically change the time-step. It is better to use the variable time stepping method to control the CFL under limit. The solution will be stable with the variable time stepping method.

      Thank you


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