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-   -   Do we need to run the steady condition first? (http://www.cfd-online.com/Forums/fluent/43585-do-we-need-run-steady-condition-first.html)

kk February 1, 2007 13:31

Do we need to run the steady condition first?
 
Hi, Do we need to run the steady conditon first and use the results as the initial guess for the unsteady flow? e.g. do I need to run a steady k-e model first and then I can run the unsteady k-e model or the LES model. It will reduce the computatinal time. But it seems the converge critia could not be met in some case. Any advice is welcome!

Thanks in advance KK

Seeker Phil February 1, 2007 14:22

Re: Do we need to run the steady condition first?
 
Hi KK, It is not absolutely necessary to run the steady case first. However,as you have mentioned it does help to start from a solution that you have already obtained as opposed to an initial guess simply because it reduces the computational complexity of the problem. There could be many reasons for not reaching convergence criteria and not just the unsteadiness in the problem.

Phil

kk February 1, 2007 15:02

Re: Do we need to run the steady condition first?
 
In my case, I get the steady result and run LES on my model. Strangely, the continuity could not reach the convergence criteria anymore. Is it possible due to my too long time step size?


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