CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   CFX (http://www.cfd-online.com/Forums/cfx/)
-   -   Fatal overflow in linear solver (http://www.cfd-online.com/Forums/cfx/124120-fatal-overflow-linear-solver.html)

alinik September 27, 2013 15:01

Fatal overflow in linear solver
 
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

MUMMED September 28, 2013 13:27

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

oj.bulmer September 30, 2013 09:42

Did you try with local timescales?

ghorrocks September 30, 2013 18:21

This is an FAQ: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

alinik October 9, 2013 02:39

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.

alinik October 9, 2013 02:49

Quote:

Originally Posted by MUMMED (Post 454074)
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?

Thanks

ghorrocks October 9, 2013 05:39

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.


All times are GMT -4. The time now is 20:44.