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-   -   Time step when scaling up. (http://www.cfd-online.com/Forums/main/81192-time-step-when-scaling-up.html)

LeCatnip October 19, 2010 09:32

Time step when scaling up.
 
Hi there.

Im new to the forum, I have been attempting to scale a simple flow from a small scale to scaling up using a scale factor of 20,000 to a larger scale. I have achieved good results from the small scale models but not for the large.

The large scale works ok when using the same inlet speed as the small scale, but then I am deviding the inlet speed by 20,000 in order to re-create the same reynolds number, and this gives pretty crazy results. My question is should I also multiply the time step by a factor of 20,000 if i reduce the inlet speed by a factor of 20,000? And do i need to change the K and epsilon values for the Reynolds Stress turbulence model which I am using?

Thanks for your help. I hope that was clear enough.

Craig.


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