Hello everybody,
I ran a view coupled simulations with Code_Saturne and Syrthes already. To speed up the simulation I often used different time steps for the codes and used a Time Step Factor in Code_Saturne. I always got good results by doing that.
I approximately can guess what this Time Step Factor is doing, but I do not completely understand it. At the moment I just know that it works. Can someone explain to me, what it does? Will I always get a wrong time related behavior? Are there any limits for the Time Step Factor?
Thank you in advance!
Martin
Different time steps in CS and Syrthes
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Mickael Hassanaly
Re: Different time steps in CS and Syrthes
Hello,
If you are in a steady computation what's you are doing is ok. This separate the dynamic from the scalars. You can't know the limits for the time step factor. But if you're dynamics is strongly linked to your scalars (through density for thermal scalar as example) it would be better to use a minor time step factor.
But if you are looking for transient flow, you should use it carefully. It's better to put time step factor equal to 1 and to have the same time steps for Code_Saturne and Syrthes.
Best regards
Mickaël Hassanaly
If you are in a steady computation what's you are doing is ok. This separate the dynamic from the scalars. You can't know the limits for the time step factor. But if you're dynamics is strongly linked to your scalars (through density for thermal scalar as example) it would be better to use a minor time step factor.
But if you are looking for transient flow, you should use it carefully. It's better to put time step factor equal to 1 and to have the same time steps for Code_Saturne and Syrthes.
Best regards
Mickaël Hassanaly
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Yvan Fournier
Re: Different time steps in CS and Syrthes
Hello,
We've had a few discussions about the time step factor with the SYRTHES developers, and though it may be quite useful, it is quite a subtle notion, which you may use only if the dynamic and thermal phenomena in the fluid have different time scales. The Code_Saturne time step*the time step multiplier should match the SYRTHES time step. So in fact, a time step factor may be also used for transients, but only if you are careful.
In the next version of the Code_Saturne/SYRTHES coupling (Code_Saturne 2.1/SYRTHES4), which should be available in a few weeks, we might just have time to make this time step multiplier more automatic (so that it also works with time varying time steps).
Best regards,
Yvan Fournier
We've had a few discussions about the time step factor with the SYRTHES developers, and though it may be quite useful, it is quite a subtle notion, which you may use only if the dynamic and thermal phenomena in the fluid have different time scales. The Code_Saturne time step*the time step multiplier should match the SYRTHES time step. So in fact, a time step factor may be also used for transients, but only if you are careful.
In the next version of the Code_Saturne/SYRTHES coupling (Code_Saturne 2.1/SYRTHES4), which should be available in a few weeks, we might just have time to make this time step multiplier more automatic (so that it also works with time varying time steps).
Best regards,
Yvan Fournier
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Laurent Malod-Panisset
Re: Different time steps in CS and Syrthes
Hi
Just checking: you mention Code_Saturne 2.1 but it looks like 2.0.1 has not been really released yet: code is there but it is mentioned in the posts that the documentation was still being checked prior to an official release on the forum.
In any case, if 2.1 could be out soon, could you tell:
a. what do you mean by "a few weeks"?
b. if it could include the compressible module in the GUI?
In any case, thanks for the software and the help on the forums
Regards
Just checking: you mention Code_Saturne 2.1 but it looks like 2.0.1 has not been really released yet: code is there but it is mentioned in the posts that the documentation was still being checked prior to an official release on the forum.
In any case, if 2.1 could be out soon, could you tell:
a. what do you mean by "a few weeks"?
b. if it could include the compressible module in the GUI?
In any case, thanks for the software and the help on the forums
Regards