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Facing a floating point error when reducing time step in a unsteady simulation

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Old   April 6, 2016, 12:55
Unhappy floating point error when reducing time step in an unsteady simulation
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lailai
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Hi, everyone,

I'm running a unsteady simulation of a valve closure process using DFBI and overset mesh. The simulation runs well with time step 2ms, 1ms, 0.5ms. But an error occurs when I tried time step 0.25ms.

The error message is "A floating point exception has occurred: floating point exception [Invalid operation]. The specific cause cannot be identified. Please refer to the troubleshooting section of the User's Guide.
Context: star.keturb.KeTurbSolver
Command: RunSimulation
error: Server Error"

I tried increase the maximum inner iteration, but didn't work.

I am using implicit unsteady, 2nd-order temporal discretization, K-E turbulence model, reliazable K-E two layer. The mesh continua is trimmed mesher and prism layer.

Can anyone give some explanation or solutions?   Thank you.

Last edited by withwolf; April 7, 2016 at 16:02.
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Old   April 11, 2016, 21:09
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Can any one give some suggestions?


I'm at my wits' end.
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Old   April 18, 2016, 02:06
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tuvia milshtein
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Try to decrease the under relaxation factor of the KE turbulence in solvers
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Old   April 23, 2016, 15:01
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Quote:
Originally Posted by sarahtuvia View Post
Try to decrease the under relaxation factor of the KE turbulence in solvers
Thank you for your reply.

I've already tried that. I decreased the KE turbulence relaxation factor from defaulted 0.8 to 0.2. But got the same error again.
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Old   November 9, 2018, 13:40
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Hey, I am getting same error. Did you get any answer ?
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Old   November 10, 2018, 17:11
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Stop the simulation before the error came up.
Make a Threshold for some physical values and then look for the too high values...
Then decide is it a mesh issue or a iteration/time step issue.
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Old   November 14, 2018, 16:33
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Yes, it might be a mesh issue. You can try plotting different residuals to see where the highest are or some unrealistic values and pin point which cells might need to be fixed.
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Old   November 14, 2018, 19:38
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Hi, wolf

I use starccm+ to solve shiphydrodynamics. I found the 2nd order sometimes cannot work. please try 1first-order temporal discretization.

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