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Define time step

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Old   January 31, 2008, 15:02
Default Define time step
  #1
Pepe
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Hello,

I'd like to increase the time step in my transient simulation. But when I do that the calculation becomes unstable and diverge although it's an implicit calculation (thought in that case the Courant-number is not the crucial part).

Is there anyway to increase the time step?

Thanks!
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Old   February 1, 2008, 10:49
Default Re: Define time step
  #2
murash-v
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If you are use mars schem you can encrease blending factor for example up to 0.9. Another method is use switch/real constants parametres, but such numbers are usually unknown, so you must wright email for autors. Also for this method autors not garant validate data.
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Old   February 1, 2008, 12:39
Default Re: Define time step
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James
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PISO typically works 'fastest' at around 4 corrector stages per time step, if you get the longest time step that does 4 PISO stages (typically with max Courant ~100) you will get about the best CPU time versus simulation time that you can.
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Old   February 3, 2008, 11:26
Default Re: Define time step
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Pauli
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1) Increase your mesh size. In particular, increase the size of small cells in high velocity regions.

2) Run UD discretization.

3) Watch for non-physical results. In other words, this may let your simulation run faster (larger step size) but might not give you a usable answer.

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