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Avoiding divergence in a transient run Fluent

    • ALEXANDRE COSTA
      Subscriber

      Hi All,

      I am having divergence issue after 0.3 s (around 30000 iterations) for a transient run in Fluent:

    • Rob
      Forum Moderator
      That's been struggling for the last several time steps. Assuming you have the data file saved have a look at what's going on. I suspect something is changing more quickly than the time step can resolve, so it's probable that you'll want to reduce the time step. For P-V coupling you may find PISO to be more efficient, the PBCS doesn't give much (if any) benefit on a transient run.
    • Akshat Jain
      Subscriber

      I used PISO , and calculated time step from strouhalt number, my calculations always has a floating point exception because the solution diverges. 
      I am simulating a water cooled cold plate and I am using a udf for my heat flux (heat flux varies with time and i imported a text file).

    • Rob
      Forum Moderator

      Turn off the UDF and see what happens - when models fail always switch off models until it works, then work out which model(s) cause the problem. 

    • Akshat Jain
      Subscriber

      It works when i input a constant value for heat flux. I import my data from a txt file (using the read-transient-table function), i don't know how to diagnose what is wrong with that process

    • Akshat Jain
      Subscriber

      this is the data i use for getting the values

    • Rob
      Forum Moderator

      Ah, you want to use a transient profile and not have repeat values in the time column - use an extra decimal place when you alter the formatting to suit a profile. 

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