Les

kharnabnew · June 17, 2014, 00:59

Dear all,
I would like to understand what kind of results does fluent provide when applying Large Eddy Simulation with the dynamics SGS model. Are the resulting fields in Fluent just the resolved ones? do they include the modeled part?
Thanks

sbaffini · June 17, 2014, 14:18

Dear khar,

the resulting fields provided by Fluent with the LES model are, as for all the codes i know, the resolved fields. That is, the implicitly filtered fields due to the top-hat filter implied by the Finite volume formulation + the implicit filter due to the grid resolution + the implicit filter due to the numerics + the still somehow implicit filter due to the SGS model itself (as it also damps some of the smallest resolved scales, or at least it is supposed to do so).

Some of the filtered scales, more specifically those due to the finite volume top-hat filter, could be recovered on the given grid but this is not done in Fluent. All the other scales are not actually recoverable and any attempt to do so must necessarily imply some modeling (e.g., the used SGS model itself or any other suitable model).

This does not depend from the SGS model itself but from the adopted approach and, in the end, by the convenience to do differently.

June 17, 2014, 00:59	Les	#1
kharnabnew Member khar nab Join Date: Sep 2009 Posts: 34 Rep Power: 16	Dear all, I would like to understand what kind of results does fluent provide when applying Large Eddy Simulation with the dynamics SGS model. Are the resulting fields in Fluent just the resolved ones? do they include the modeled part? Thanks

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June 17, 2014, 14:18		#2
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,151 Blog Entries: 29 Rep Power: 39	Dear khar, the resulting fields provided by Fluent with the LES model are, as for all the codes i know, the resolved fields. That is, the implicitly filtered fields due to the top-hat filter implied by the Finite volume formulation + the implicit filter due to the grid resolution + the implicit filter due to the numerics + the still somehow implicit filter due to the SGS model itself (as it also damps some of the smallest resolved scales, or at least it is supposed to do so). Some of the filtered scales, more specifically those due to the finite volume top-hat filter, could be recovered on the given grid but this is not done in Fluent. All the other scales are not actually recoverable and any attempt to do so must necessarily imply some modeling (e.g., the used SGS model itself or any other suitable model). This does not depend from the SGS model itself but from the adopted approach and, in the end, by the convenience to do differently.