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change timestep after a certain iteration number |
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May 31, 2007, 06:03 |
change timestep after a certain iteration number
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#1 |
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Hi, I observe that my problem starts to diverge after say 60-70 iterations, but it is soon rectified when I reduce the timestep. But during a batch run I would like to do the same. Is it possible to change the timestep after a specified iteration during a batch run (command line)?
Thanks... |
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May 31, 2007, 09:12 |
Re: change timestep after a certain iteration numb
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#2 |
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I do it every day....
Physical Timescale = min(1e-2[s],max(5e-3[s],2e-2[s]-citern*1e-4[s])) Plot it in Pre to find out how it looks like. Gert-Jan www.bunova.nl |
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June 1, 2007, 01:58 |
Re: change timestep after a certain iteration numb
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#3 |
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Thanks a lot Gert-Jan,
Now it strikes me...or inturn I can also use a fuction in PRE |
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June 1, 2007, 04:27 |
Re: change timestep after a certain iteration numb
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#4 |
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Hi! Gert-Jan, I think This is also useful to me, could you please explain the meaning of "min(1e-2[s],max(5e-3[s],2e-2[s]-citern*1e-4[s]))", since I am quite new to CFX. Thanks
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June 1, 2007, 05:56 |
Re: change timestep after a certain iteration numb
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#5 |
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It is mathematics. The only unknown thing is citern which is the current iteration number. You can also use aitern which is the accumulated iteration number.
Just play around in Pre or a spreadheet to see what the function does... Gert-Jan www.bunova.nl |
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June 3, 2007, 06:17 |
Re: change timestep after a certain iteration numb
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#6 |
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Hi. There is another way is to use step function. suppose timestep upto 60th iteration is 0.025 [s] and after 60th iteration it is tobe reduced to 0.002 [s], you may use following step function, Timestep = 0.025[s]*step(aitern-60)+0.002[s]*step(60-aitern).
Sameer |
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