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Old   September 27, 2013, 15:01
Default Fatal overflow in linear solver
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ali
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Hi,

I am simulating air flow around a turbine blade. I can obtain the solution when turbulence model is set to K-epsilon and K-Omega. When I want to run the case with SST, I receive the following error message. The solver crashes in the very first iteration.
The simulation is steady state. I have reduced the timescale factor to 1e-6 and moved the boundaries away from the blade and also increased the memory allocation factor.

p, li { white-space: pre-wrap; } +--------------------------------------------------------------------+
| ERROR #004100018 has occurred in subroutine FINMES. |
| Message: |
| Fatal overflow in linear solver. |
+--------------------------------------------------------------------+


Any suggestions?


Thanks
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Old   September 28, 2013, 13:27
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Mohamad Alagheband
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if your mesh is quite fine ,try changing relaxation factors.
I've got this problem,different case ,after changing relaxation factors in expert parameter it started to run
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Old   September 30, 2013, 09:42
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Did you try with local timescales?
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Old   September 30, 2013, 18:21
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Glenn Horrocks
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This is an FAQ: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F
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Old   October 9, 2013, 02:39
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Thanks,

I fixed that issue for steady state case. Now that I want to solve the case for transient case I receive the exact same error again. Now what I can do?
I have tried decreasing time step size and used the steady case solution for initializing the domain.
Generally what should one do when encountered by this error in transient simulations? We do not have physical timescales any more to play with to overcome this error and obtain solution.
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Old   October 9, 2013, 02:49
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Quote:
Originally Posted by MUMMED View Post
if your mesh is quite fine ,try changing relaxation factors.
I've got this problem,different case ,after changing relaxation factors in expert parameter it started to run

Thanks. I solved this issue for steady case but still have problem in unsteady case. Where in expert parameters I can set underrelaxation factor? I cannot find it.

Btw what is the difference between underrelaxation factor and physical timescale for steady simulation?

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Old   October 9, 2013, 05:39
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Quote:
Generally what should one do when encountered by this error in transient simulations?
Ummm - did you read the FAQ link I posted? The only difference for a transient simulation is you decrease the actual timestep size rather than the pseudo timestep size. Other than that it is all the same.

Quote:
Generally what should one do when encountered by this error in transient simulations?
That is because CFX is not a SIMPLE based solver where the first thing you do when you have convergence difficulties is reduce the under relaxation factors. You do not adjust under relaxation with CFX, rather you adjust the time step size.
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