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Convergence problem

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Old   May 17, 2007, 04:17
Default Convergence problem
  #1
akr
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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
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Old   May 17, 2007, 05:21
Default Re: Convergence problem
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Adriano
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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
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Old   May 17, 2007, 11:27
Default Re: Convergence problem
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Madhukar
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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
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Old   May 17, 2007, 21:59
Default Re: Convergence problem
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akr
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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
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Old   May 18, 2007, 08:21
Default Re: Convergence problem
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Madhukar
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Give a try with standard K-Eps Model

Regards

Madhukar
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Old   May 19, 2007, 03:24
Default Re: Convergence problem
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akr
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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
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Old   May 22, 2007, 08:49
Default Re: Convergence problem
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Madhukar
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Hi,

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

regards
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