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-   -   One question about the cfx 5 best practices (http://www.cfd-online.com/Forums/cfx/21526-one-question-about-cfx-5-best-practices.html)

John August 17, 2005 00:11

One question about the cfx 5 best practices
 
Hello, everyone

In cfx best practices for multiphase flow , I found following tips:

"Convergence Tips: Sometimes, physical instabilities (such as recirculation zones) can result in slow or stalled convergence. In these cases, you can still obtain an indicator of convergence for a global quantity by creating a monitor point at some point in the domain. As a result, you can determine whether values for selected global quantities (such as gas hold-up) are meaningful."

My english is just not good enough to help me understanding above tip. When I do a multiphase modelling, does above mean that no matter the convergence criteria are met or not, I can always say the simulation is converged if the selected global quantities (such as gas hold-up) at the monitoring points become stable?

Do I understand that correctly?

Thanks for your comments.

Regards!

John


John August 18, 2005 17:44

Re: One question about the cfx 5 best practices
 
The tips can be found in Page 145 of "CFX-5 Best Practices Guide for Multiphase"

Hope sombody can give explainations.

Thanks!


Glenn Horrocks August 18, 2005 18:30

Re: One question about the cfx 5 best practices
 
Hi,

No, if the values at a specific point have converged then you cannot then assume the whole simulation is converged. Other areas of the flow may not yet have converged.

Also, make sure you know the difference between a converged solution and an accurate solution. It is very easy to get a converged solution with a coarse mesh and upwind differencing, but it will not be accurate.

Regards, Glenn Horrocks


John August 18, 2005 18:39

Re: One question about the cfx 5 best practices
 
Thanks Glenn for your comments. I understand and agree what you said. But could you please explain the tips shown in CFX best practise. What does it exactly mean?

I still fell confused about that.

Thanks and best regards!

John


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