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-   -   Fluidized Bed: Error: Divergence detected in AMG solver: pressure correction Error Ob (http://www.cfd-online.com/Forums/fluent/105833-fluidized-bed-error-divergence-detected-amg-solver-pressure-correction-error-ob.html)

Mole89 August 10, 2012 06:33

Fluidized Bed: Error: Divergence detected in AMG solver: pressure correction Error Ob
 
Hey,

i am trying to simulate a solid-gas fluidized bed by using a UDF for Drag coefficent. If i simulate with syamlal for drag coefficient there is no problem. But if i use a UDF i allways get the following error:

reversed flow in 28 faces on pressure-outlet 3.
# Divergence detected in AMG solver: mp-x-momentum -> Decreasing coarsening group size!
# Divergence detected in AMG solver: mp-x-momentum -> Increasing relaxation sweeps!
# Divergence detected in AMG solver: pressure correction -> Turning off correction scaling!
# Divergence detected in AMG solver: pressure correction -> Increasing relaxation sweeps!

Error: Divergence detected in AMG solver: pressure correction
Error Object: #f


I have no idea how to fix this problem, i allready tried to lower the under-relaxation factors, but this didn't work. Maybe somebody can help me?

Best regards

ravindra October 9, 2012 08:07

hey hi
i am having the same problem of
Divergence detected in AMG solver: pressure correction
while i am using udf for radial distribution in fluidised bed reactor,but custom drag function is working well.


did u find out the solution to this problem ....if u have then kindly reply ...

Maryam.SUT October 9, 2012 08:34

Hi everyone
I am simulating gas-solid fluidized bed, but there is reversed flow in pressure-outlet boundary and finally the solution does not converge.

I wonder if u model transient flow, which kind of time stepping u used, and what the order of magnitude your time-step is. in several papers i saw they used adaptive time stepping which can't be used in Eulerian multiphase model..

hkhosravi November 17, 2012 16:20

Quote:

Originally Posted by Maryam.SUT (Post 385714)
Hi everyone
I am simulating gas-solid fluidized bed, but there is reversed flow in pressure-outlet boundary and finally the solution does not converge.

I wonder if u model transient flow, which kind of time stepping u used, and what the order of magnitude your time-step is. in several papers i saw they used adaptive time stepping which can't be used in Eulerian multiphase model..

I simulated FB with dt=0.0001. there was reverse flow in my simulation but converged with this dt and the reslts was very accurate.

shahid nadeem April 12, 2014 07:04

Fluidized bed for cooling tower
 
I am working on FB for cooling tower i am also getting same error could you please tell me if u have resolved the problem and also can anyone tell me how to give a water spray inside the Fluidized Bed

Maryam.SUT April 12, 2014 09:32

set the time step 1E-5, and under relaxation factor for all variables 0.2.


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