Fluent native GPU solver: under-relaxation factors?

- February 2, 2023 at 1:40 pm
  
  martin.kocijancic
  Subscriber
  
  I recently started using the native GPU solver. So far I used it only on stady-state RANS (SST k-omega) case.
  I was wondering what are the recommended under-relaxation factors for steady case when using GPU solver and SIMPLE scheme.
  Is it normal, that the exact same case takes more iterations to converge with GPU solver compared to classic CPU solver? 2~3 times more iterations. But less time of course.
- February 3, 2023 at 9:38 am
  
  Rob
  Ansys Employee
  
  Check you're running the cpu solver in SIMPLE too, the default is PBCS so will take fewer iterations.
  For UR factors you may want to adjust turbulence and momentum, it's a little problem dependent so other than default we don't have a guideline document as yet.
- February 6, 2023 at 11:13 am
  
  martin.kocijancic
  Subscriber
  
  Thank you Rob. Yes, I was running CPU solver SIMPLE. Did you observe equal number of iterations with CPU and GPU solver on your case?
  I will play around with UR factors of turbulence and momentum if they help me stabilise the simulation quicker.
- February 6, 2023 at 12:07 pm
  
  Rob
  Ansys Employee
  
  It should be near enough, I'm not using the GPU solver as most of what I do isn't yet available.

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