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-   -   Convergence problem (https://www.cfd-online.com/Forums/fluent/44731-convergence-problem.html)

akr May 17, 2007 04:17

Convergence problem
 
Hi, I want to solve gas flow in chamber. The geometry of chamber is 0.3 in width, 0.3 in height and 0.05 m in depth. The inlet is circle whose diameter is 0.013 m and set on the side face (0.3 by 0.05 m). The outlet is also circle whose diameter is 0.013 m and set on top face (0.3 by 0.05 m). The inlet is velocity inlet boundary and the velocity is 2.5 m/s. The outlet is pressure outlet boundary. And I am solving with laminar model. When this calculation starts, the residual decrease to 10-2. But after that, the residual keeps flat and never decrese. Is this converge? Thanks, akr

Adriano May 17, 2007 05:21

Re: Convergence problem
 
Hi, Try to check the under relaxation factors (reducing them), try to change discretization scheme and pressure-velocity coupling scheme (i.e.: Simple). After, If You don't reach convergence, check your mesh!

Hope it's helpful,

best regards Adriano

Madhukar May 17, 2007 11:27

Re: Convergence problem
 
Hi

U had the same question, which i had 2 days back.... there was a small but valuable discussion on this topic yesturday in the forum...you can find it under

http://www.cfd-online.com/Forum/fluent.cgi?read=48852

regards

akr May 17, 2007 21:59

Re: Convergence problem
 
Thank you for your responses. I will also try to use turbulence model instead of laminar model. But now what I don't understand is which model is best for my case. In my case, reynolds number is about 3000 at inlet. Do you know which one is best??

Regards, akr

Madhukar May 18, 2007 08:21

Re: Convergence problem
 
Give a try with standard K-Eps Model

Regards

Madhukar

akr May 19, 2007 03:24

Re: Convergence problem
 
Hi Madhukar,

Is it O.K. to use standard K-Eps model in my case? In the chamber, fluid velocity is not high. And reynolds number is small.

Regards, akr

Madhukar May 22, 2007 08:49

Re: Convergence problem
 
Hi,

If the Reynold's number is very less ....you try with RNG K-Eps., model.

regards


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