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-   -   Turbulence quantities solved by 1st order scheme? (http://www.cfd-online.com/Forums/cfx/24037-turbulence-quantities-solved-1st-order-scheme.html)

Damien May 27, 2007 10:45

Turbulence quantities solved by 1st order scheme?
 
Hi,

I read some previous post that the turbulence quantities in CFX were solved using first order scheme. Is that because of the time derivative term in the turbulence equation and the first order scheme has to be used to ensure bounded solution?

Thanks for your kind advice.

Gert-Jan May 27, 2007 16:34

Re: Turbulence quantities solved by 1st order sche
 
For turbulence, production and dissipation are more important than convection. In other words, turbulence is hardly transported by the flow. Therefore, usually upwind is sufficient.

However, if you want to want to study mixing (reactions of chemical component. scalars, energy. etc.) you might need to check high resolution. I have seen applications where this lead to considerable improvements.

Gert-Jan

www.bunova.nl

Damien May 29, 2007 01:56

Re: Turbulence quantities solved by 1st order sche
 
Okay, thanks. If I choose high resolution scheme, it should now be 2nd order, right? I remember someone in this forum mentioned that turbulence equation is always solved in first order. I'm a bit confused now.

Gert-Jan May 29, 2007 07:54

Re: Turbulence quantities solved by 1st order sche
 
Close to second order. You can check the order by looking for the beta value in CFX-Post. If you really want 2nd order, then you should choose a specific blend factor of 1.

Gert-Jan


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