Divergence detected in AMG for temperature

    • Dino


      I have a UDF with DEFINE_INIT, DEFINE_ADJUST, and two DEFINE_SOURCE (one for a UDS and one for the energy equation). When I initialize and run, I get this message. If I take a very small timestep, it works but after let's say 1e5 seconds flow time, it shows the same message. What reasons could be cause for this error, please?

      Thank you,

    • seeta gunti
      Ansys Employee

      Helo Dino,

      Good Day!

      I understand that you are getting divergence in temperature and UDS-0. One option is to try with lower URFs but energy, it may take long time to converge. So you switch off the secondary gradients for energy equation by using following TUI command.

      (rpsetvar 'temperature/secondary-gradient? #f)

       Secondly we can try reducing the explicit URFs of energy by using the following commands.

      (rpsetvar 'explicit-relaxation? #t)

      (rpsetvar 'temperature/explicit-relax 0.2)


      For UDS, you can reduce the under relaxation factor and try running the case. Hope this will help you to avoid the divergence in temperature and UDS.


      Thanks & Regards,



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