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-   -   HELP DIVERGENCE NITA!! (http://www.cfd-online.com/Forums/fluent/46199-help-divergence-nita.html)

Hadi October 1, 2007 10:59

HELP DIVERGENCE NITA!!
 
Hi to all,

I am running, LES channel flow, i ran K-epsilon by fixing a constant flow rate, and then i applied the perturbation,when running LES, after few iterations the bulk velocity will increase from 1m/s to 30 m/s ,then it changes its direction,and the simulation blows!! By looking to the residuals the contiuity is always increasing.

I ran the same simulation using another code and i didn't face any problem, so i think the mesh is ok, and the courant number is less then 0.25! can you please tell em what might be wrong.

Any help will be appreciated!

Cheers Hadi

Jim October 2, 2007 05:18

Re: HELP DIVERGENCE NITA!!
 
Do you encounter reversed flow problem? And does the problem come from the near-wall?

Hadi October 2, 2007 06:23

Re: HELP DIVERGENCE NITA!!
 
Well maybe i found the solution, i am not sure though. When you specify a constant mass flow rate, iterations are needed to adjust the flow at each time-step, NITA is a non iterative scheme, so it only works by fixing a constant pressure gradient.

i encountered a reversed flow, but i think it is a numerical error.

I am running now the simulation without NITA, and till now it is working well.

What about your simulation?


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