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

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Old   August 10, 2012, 06:33
Default Fluidized Bed: Error: Divergence detected in AMG solver: pressure correction Error Ob
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Fabian
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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
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Old   October 9, 2012, 08:07
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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 ...
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Old   October 9, 2012, 08:34
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Maryam
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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..
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Old   November 17, 2012, 16:20
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Quote:
Originally Posted by Maryam.SUT View Post
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.
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Old   April 12, 2014, 07:04
Smile Fluidized bed for cooling tower
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shahid
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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
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Old   April 12, 2014, 09:32
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set the time step 1E-5, and under relaxation factor for all variables 0.2.
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