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-   -   Under Relaxation Factor Range (http://www.cfd-online.com/Forums/fluent/111181-under-relaxation-factor-range.html)

aminshams December 30, 2012 12:25

Under Relaxation Factor Range
 
Hi everyone
I'm simulating mass flow distribution in micro-channel manifolds.
The solution does not converge unless I change the Momentum Under Relaxation Factor. I read somewhere in this forum that we are not allowed to decrease the Momentum URF less than 0.5 But as I decrease it less than 0.5 the solution converges faster. Is it OK to reduce URF this way?
I encountered an other problem too. Although the residuals are less than 1e-04, there is obvious different in mass flow rate in different number of iterations.
could you please help me?:(

Regards,
Amin

msaeedsadeghi December 31, 2012 00:33

For Microchannel, first use double precision, second decrease URF of the UDF for wall slip profile. It's easy to converge it. Try more :)

rasoulb January 6, 2013 16:48

Quote:

Originally Posted by msaeedsadeghi (Post 399497)
For Microchannel, first use double precision, second decrease URF of the UDF for wall slip profile. It's easy to converge it. Try more :)

Hi,

I want to simulate turbulent channel flow with slip B.C (by LES), But the problem doesn't converge, so can you guide me for URF for momentum & pressure? if you have any other comment, please write it.

Thanks

LuckyTran January 7, 2013 01:09

Quote:

Originally Posted by rasoulb (Post 400369)
Hi,

I want to simulate turbulent channel flow with slip B.C (by LES), But the problem doesn't converge, so can you guide me for URF for momentum & pressure? if you have any other comment, please write it.

Thanks

You shouldn't ever touch the URF if you are doing LES since it is a transient simulation. If anything, you want to increase URF and make it ORF.


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