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-   -   Divergence detected in AMG & FMG solver..... (http://www.cfd-online.com/Forums/fluent/83782-divergence-detected-amg-fmg-solver.html)

devesh.baghel January 11, 2011 07:34

Divergence detected in AMG & FMG solver.....
 
Hi,

I am doing simulation of a manifold. first I am running the analysis with first order upwind scheme & constant density. Once the flow field get stabilized, I switched over to material property Ideal Gas & relaxation factor to 2nd order for momentum, pressure & energy as well, then it is throwing a message:
“Divergence detected in AMG solver: pressure correction -> increasing relaxation sweeps!
Absolute pressure limited to 1.000000e+00 in 1 cells on zone 1
Turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 53 cells

I tried options like:
1. Reduced the Relaxation factor.
2. kept pressure & energy Descritization scheme as default.
3. tried with FMG instead of AMG for initialization.

but no still on the same surface.....:(
Please, share some idea to solve this problem.
Thanks in advance

spak January 17, 2011 02:58

While executing iterations there are constantly occuring errors as
1. Turbulent viscosity limited to.....
2. Absolute pressure limited to....
3. Temperature limited to...
4. Reverse flow in....
5. Divergence detected in AMG solver: temperature / pressure correction
After the divergence error, the iterations come to a halt.

We are solving in Pressure based solver following the K-epsilon method and Enhanced Wall Functions and are solving in steady state with given conditions as
Inlet Pressure: 92000 Pa
Stage Pressure Ratio: 1.35
Mass Flow Rate: 22 kg/s
Rotor speed (RPM): 6465
STP conditions

We have also tried using Coupled solver for Pressure- Momentum Coupling and also tried changing solver limits.
Kindly do reply as soon as possible.


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