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Old   February 27, 2010, 07:52
Unhappy Fluent problems
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Gary Burns
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Im busy doing a CFD problem for my university degree.

The problem Ive modeled is a simple box which is half full water. It has a inlet at the bottom and a outlet at the top. The inlet pumps water in at a velocity of 0.9m/s.

When solving I had the following problem.

During the iterations it was saying
"reversed flow in 367 faces on pressure-outlet 25" The numebr is different each time and ranges from 1 to 1900.
however this didnt cause a error.

I did get an error as the Global Courant number was greater than 250 therfore I decreased the timestep size as recommended.

However after a few more iterations I got the following error:

# 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

Does anyone konow what this means????

Many Thanks
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Old   May 6, 2014, 06:51
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Mahesh J Rao
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Probably the water coming inside from the bottom would increase the static pressure to counter the dynamic pressure and cause a reversed flow.

AMG solvers are Algebraic Multigrid Solvers which takes care of adaptive mesh refinement.

More about AMG solver divergence is discussed in this thread:
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Old   May 8, 2014, 04:04
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Junphy Liues
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this error is very common when couple with multiphase simulation. you 'd better check your settings and use the case check function to find if your settings are suitable with your case. when this error occurs, there always at least one setting is out of calculation, usually the pressure or the temperature is greater than the solver can deal with.
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