# Convergence problem

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 May 17, 2007, 03:17 Convergence problem #1 akr Guest   Posts: n/a 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

 May 17, 2007, 04:21 Re: Convergence problem #2 Adriano Guest   Posts: n/a 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

 May 17, 2007, 10:27 Re: Convergence problem #3 Madhukar Guest   Posts: n/a 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

 May 17, 2007, 20:59 Re: Convergence problem #4 akr Guest   Posts: n/a 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

 May 18, 2007, 07:21 Re: Convergence problem #5 Madhukar Guest   Posts: n/a Give a try with standard K-Eps Model Regards Madhukar

 May 19, 2007, 02:24 Re: Convergence problem #6 akr Guest   Posts: n/a 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

 May 22, 2007, 07:49 Re: Convergence problem #7 Madhukar Guest   Posts: n/a Hi, If the Reynold's number is very less ....you try with RNG K-Eps., model. regards

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