Error: Divergence detected in AMG solver

Masroor · November 15, 2015, 03:01

Hi,
I need to discuss a matter that I faced while simulating a multiphase system using different multiphase and turbulence models. In all the cases I kept the operating conditions and under relaxation factors similar. I got corrected results without any error using eulerian model with k-epsilon standard, k-omega standard models while the case including same multiphase model but RS turbulence model yielded an error "Error: Divergence detected in AMG solver: epsilon" with a notification in text user interface which is "turbulent viscosity limited to viscosity ratio of 1.0 e+05 in xxxxx cells".
Kindly provide any any solution for above mentioned

LuckyTran · November 16, 2015, 10:50

Two things are going on here. The first is that your solution diverged, it's as simple as that. The RSM model is notoriously difficult to get a converged solution because it is very sensitive. You should investigate whether it converged because of a bad initial guess or if there is another numerical issue that is causing the issue (skewed cells in mesh for example). You may be able to proceed using reduced urf's.

Turbulent viscosity being limited means that your turbulence model is predicting highly non-physical results, and this can be a result of a bad initial guess. For example, if you didn't properly initialize all the Reynolds stresses & k & epsilon you could easily end up with this error.

November 15, 2015, 03:01	Error: Divergence detected in AMG solver	#1
Masroor New Member Masroor Join Date: Nov 2015 Posts: 10 Rep Power: 10	Hi, I need to discuss a matter that I faced while simulating a multiphase system using different multiphase and turbulence models. In all the cases I kept the operating conditions and under relaxation factors similar. I got corrected results without any error using eulerian model with k-epsilon standard, k-omega standard models while the case including same multiphase model but RS turbulence model yielded an error "Error: Divergence detected in AMG solver: epsilon" with a notification in text user interface which is "turbulent viscosity limited to viscosity ratio of 1.0 e+05 in xxxxx cells". Kindly provide any any solution for above mentioned

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November 16, 2015, 10:50		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 65	Two things are going on here. The first is that your solution diverged, it's as simple as that. The RSM model is notoriously difficult to get a converged solution because it is very sensitive. You should investigate whether it converged because of a bad initial guess or if there is another numerical issue that is causing the issue (skewed cells in mesh for example). You may be able to proceed using reduced urf's. Turbulent viscosity being limited means that your turbulence model is predicting highly non-physical results, and this can be a result of a bad initial guess. For example, if you didn't properly initialize all the Reynolds stresses & k & epsilon you could easily end up with this error.