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Divergence detected in AMG solver

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Old   January 7, 2013, 01:26
Smile Divergence detected in AMG solver
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Mary
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Hi everyone,
I'm trying to simulate a centrifugal compressor and i'm having some difficulties to get the convergence in pseudo transient method.But if i did not select the pseudo transient ,i can get the convergence.

I simulate the rotation using Multiple Reference Frame (MRF). The rotor has an angular velocity of 5266 rpm, and the stator is stationary.

The mesh hasnīt shown any problems when i do the mesh check.

The boundaries are defined as pressure-inlet and pressure-outlet and periodic.

and the walls are the following:
-Wall-stator: The walls of the stator are defined as stationary
-Wall-rotor: Rotating walls of the rotor, defined as moving walls, relative to adjacent cell zone, with 0 velocity.

i use hybrid initialization.

When 130 iterations, i got the following message:
# Divergence detected in AMG solver: nut -> Decreasing coarsening group size!
# Divergence detected in AMG solver: nut -> Increasing relaxation sweeps!

Error: Divergence detected in AMG solver: nut
Error Object: #f

I've uploaded an screenshot of the two final result
Could anybody help me?

Thanks.
12.jpg
13.jpg
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Old   March 27, 2013, 05:54
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楚归羽
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so do I, the same errorwrong.jpg
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Old   March 28, 2013, 13:34
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Sheng
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Lower the Courant Number and have a try. AMG means algebraic Multigrid.
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