CFD Online Discussion Forums

CFD Online Discussion Forums (
-   Main CFD Forum (
-   -   LES filter (

xing zhang November 13, 2003 23:27

LES filter
I have a question about LES.Is the 'filter' only used for theoritical analysis or it has to be implemented in the code? Nuemrical method such as FVM is a 'implicit filter', isn't it? So if the grid is fine enough, and sub-grid turbulence model is used, then it is LES, no explicit filter is needed, is that true?

Lionel Larcheveque November 14, 2003 08:13

Re: LES filter

Almost all LES are carried out without an explicit filtering of the N-S equations because the mesh and the numerical method act as implicit filters. However, some LES purists recommend to use an explicit filtering in order to reduce error in subgrid modeling.

Moreover, filters are required for some subgrid models, such as dynamic Smagorinsky : they're used to obtain a test field with higher cutoff length to take advantage of Germano's identity.

Hope this helps

Best regards.

Dean November 14, 2003 15:27

Re: LES filter
If you explicitly compute the Leonard terms, you need to specify a filter.

senthil November 15, 2003 14:50

Re: LES filter
Unless otherwise one uses dynamic family of models people donot use explicit filters. ALthough some use.

All times are GMT -4. The time now is 20:59.