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why interDyMFoam does not support backward ddt scheme?

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Old   March 3, 2016, 05:02
Default why interDyMFoam does not support backward ddt scheme?
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Yage
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Dear Foamer,

I would like to use backward second order time discretization in interDyMFoam, but the solver doest not support this time scheme.

Could someone explain the reason for that?

Many Thanks,
Yage
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Old   March 3, 2016, 05:31
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I found that the interDyMFoam support Crank-Nicolson (CN) scheme and I set the weighing factor to 1 for fully second order accuracy.

But the alphasubcycle must be 1 in this case.

Any idea about the reason?
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Old   March 3, 2016, 06:53
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hello,

This may come from the fact the backward are not a bounded scheme, and MULES need it, or that MULES aren't coded to use backward.
CN just need current and old time, so sub-cycling used in MULES may not be usable. Same for backward.

regards,
olivier
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Old   March 3, 2016, 08:16
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Quote:
Originally Posted by olivierG View Post
hello,

This may come from the fact the backward are not a bounded scheme, and MULES need it, or that MULES aren't coded to use backward.
CN just need current and old time, so sub-cycling used in MULES may not be usable. Same for backward.

regards,
olivier
Thanks for your answear
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Old   March 3, 2016, 08:18
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Quote:
Originally Posted by olivierG View Post
hello,

This may come from the fact the backward are not a bounded scheme, and MULES need it, or that MULES aren't coded to use backward.
CN just need current and old time, so sub-cycling used in MULES may not be usable. Same for backward.

regards,
olivier
and any suggestion for which one to use, 1st order ddt + sub-cycling or 2nd order ddt without sub-cycling?

Regards,
Yage
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Old   March 3, 2016, 09:26
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hello,

I would say first order for a RANS may be enough, and 2nd order with lower time step for more fine RANS/ LES case.

regards,
olivier
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Old   March 3, 2016, 13:47
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Quote:
Originally Posted by olivierG View Post
hello,

I would say first order for a RANS may be enough, and 2nd order with lower time step for more fine RANS/ LES case.

regards,
olivier
Thanks for the suggestion
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