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-   -   ke--RSM--LES--DNS? (http://www.cfd-online.com/Forums/main/2080-ke-rsm-les-dns.html)

sheng May 3, 2000 11:48

ke--RSM--LES--DNS?
 
Someone said: "we are using RSM", then the others said:"we are using LES or DNS". Does this mean that it is a technical level increase in the CFD field?

I knew the fact that the calculation time will increase from ke to DNS. But, does it mean that the quality of the simulation results also increase.

What's the current situation about the application of these four different methods in the industry?

Thanks in advance! Sheng

John C. Chien May 3, 2000 13:05

Re: ke--RSM--LES--DNS?
 
(1). We are still talking about the Reynolds averaged equations (over one hundred years old now), and the modeling of the Reynolds stresses terms (directly or through the eddy-viscosity concept. available since the days of Prandtl's mixing length theory). (2). The LES (large eddy simulation) and DNS (direct numerical simulation) are transient numerical simulation approaches. These methods are not developed for routine industrial applications. At least, not for now. (3). Whether the solutions obtained will provide accurate representation of the flow field, or will provide more information about the turbulent flows, itself is the current research subject. (4). So, when we talk about the cfd solution of turbulent flows, we mean the solution to the Reynolds averaged equations with the appropriate turbulence model for the Reynolds stresses, directly or indirectly through eddy-viscosity concept. (5). Some commercial codes may have the capability to do LES or even DNS, but these are not intended for design applications.


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