Divergence detected in AMG solver:k

thiyam · June 1, 2012, 13:27

Hi all,

I am using Eulerian multiphase model with standard k-epsilon turbulence model in gas-liquid phase, udf for drag co-efficient is interpreted successfully but when i start iteration, exactly after 11th iteration it stops showing error as

Error: divergence detected in AMG solver:k

please help

Sixkillers · June 1, 2012, 14:16

Try to reduce Courant number (I am assuming that you are using coupled solver) and also under relaxation factors (for multiphase flow it is really necessary).

Jabba · June 12, 2012, 14:15

Quote:

Originally Posted by Sixkillers

Try to reduce Courant number (I am assuming that you are using coupled solver) and also under relaxation factors (for multiphase flow it is really necessary).

How are you initiating your solution?

Maybe you can try to run a previous calculation without resolving the volume fraction (uncheck it on your Solution Controls) to get an initial field for the multiphase run then.

thiyam · June 13, 2012, 07:47

Thanks for your reply

Its running now but its not converging at all especially the gas phase residuals. Mine is pressure based solver and simulating in steady state condition and the following are the boundary conditions:

Velocity inlet -velocity of liquid=0 & volume fraction=0
-velocity of gas=0.0025m/sec & volume fraction=1
-diameter of bubble=0.002m
please check these conditions as i am little surprised when i mistakenly put gas volume fraction as zero, then the solution was run fine but when i come to know this mistake i changed the value from zero to one, it starts showing problem in convergence.

Help is needed

June 1, 2012, 13:27	Divergence detected in AMG solver:k	#1
thiyam New Member Tamphasana Join Date: Jun 2012 Posts: 9 Rep Power: 3	Hi all, I am using Eulerian multiphase model with standard k-epsilon turbulence model in gas-liquid phase, udf for drag co-efficient is interpreted successfully but when i start iteration, exactly after 11th iteration it stops showing error as Error: divergence detected in AMG solver:k please help

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June 1, 2012, 14:16		#2
Sixkillers Member Join Date: Nov 2011 Location: Czech Republic Posts: 81 Rep Power: 3	Try to reduce Courant number (I am assuming that you are using coupled solver) and also under relaxation factors (for multiphase flow it is really necessary).

June 13, 2012, 07:47		#4
thiyam New Member Tamphasana Join Date: Jun 2012 Posts: 9 Rep Power: 3	Thanks for your reply Its running now but its not converging at all especially the gas phase residuals. Mine is pressure based solver and simulating in steady state condition and the following are the boundary conditions: Velocity inlet -velocity of liquid=0 & volume fraction=0 -velocity of gas=0.0025m/sec & volume fraction=1 -diameter of bubble=0.002m please check these conditions as i am little surprised when i mistakenly put gas volume fraction as zero, then the solution was run fine but when i come to know this mistake i changed the value from zero to one, it starts showing problem in convergence. Help is needed