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Courant number 999.999

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Old   December 14, 2005, 14:27
Default Courant number 999.999
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PetrK
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Hi everybody, I'm running a transident siimulation flow over 3D wing, but after every timestep I get Courant number 999.999 and convergence is not so good. What's wrong? Turbulence - SST, inlet speed 60 m/s. Thanks for reply. PetrK
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Old   December 15, 2005, 09:25
Default Re: Courant number 999.999
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matej
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your time step is too high. look for Courant number definition in manual. If it is 999.999 it is probably much higher, but only at some places. You should get values for max and mean courant.

high value means that the timestep is too big, or the grid size is too small. So if you want that fine grid, you must go down with time step.

good luck, matej
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Old   December 15, 2005, 10:44
Default Re: Courant number 999.999
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PetrK
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Many thanks you are absolutly right, I have a fine mesh around the wing. I'll try reduce timestep by 10 times. Thanks again
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Old   December 15, 2005, 12:07
Default Re: Courant number 999.999
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Jeff
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Try reducing it by a factor of 1000. For time accurate and explicit steady-state solutions, you need a courant number of around 1 (vs. 1000). The implicite solver can handle larger than this, but its a good place to start before you start increasing it.

Jeff
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