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Residuals not converging (2D supesonic inlet)

    • felice_lucivero
      Subscriber

      Hello everybody,

      I am trying to simulate a supersonic flow throguh an air intake.

      The final aim of the project is to reproduce the results reported in a reference paper, but my residuals are not converging.

      The mesh I have used for the simulation is the following:

      The density-based (coupled) implicit double precision Fluent solver has been set.

      For the inlet I set a farfield bc with a Mach number equals to 2.41.

      For the outlet I set a pressure-outlet bc with zero pressure.

      The CFL was fixed at 0.5.

      All of these conditions come from the reference paper.

      I have also tried to switch to a pressure-based solver, but the solution get even worse.

      What might be the issue?

    • felice_lucivero
      Subscriber

      Nobody's got any idea?

    • Essence
      Ansys Employee

      Hello,

      Which turbulence model did you use? What are the controls (URFs) you set? Reduce the URFs and once stable residuals reached, turn them to default. Use FMG initialization. Also for higher order terms of discretization, please use High Order Term Relaxation (HOTR) for stable residuals. Use Psuedo time step.

      • felice_lucivero
        Subscriber

        Hello Essence,

        I used a RNG k-e model. This choice is in accord with the reference paper, I need to simulate that model for having a comparison with my results.

        I tried what you suggested and, besides that, I also lowered the order of the numerical methods (from 2nd to 1st order upwind).

        Nevertheless, there was no big improvement in the residuals:

        I brought the URFs gradually down to 0.1.

        Is it possible that there might be a problem with the BCs?

    • Essence
      Ansys Employee

      Did you use FMG initialization? Initial values in compressible flows play important role in convergence.

      • felice_lucivero
        Subscriber

        Yes, I did use FMG initialization but I did not change any parameter, I left everything as default.

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