[lucamirtanini]

Which is the difference between the Large eddy simulation and the Very Large Eddy simulation?

[FMDenaro]

Originally Posted by lucamirtanini

Which is the difference between the Large eddy simulation and the Very Large Eddy simulation?

Despite the similar nomenclature, they are fundamentally different in the idea. VLES aims to represent a good compromise between accuracy and computational costs and is more similar to the URANS formulation than a LES. The idea is that the filtering width is much bigger than in LES and the unresolved part are consequently problem dependent. In practice is like an LES code that use a very coarse grid where a small (or disregardable) part of the inertial region is solved in the energy spectra.
Of course, that means that the SGS model is no longer supposed to be universal.

[lucamirtanini]

Originally Posted by FMDenaro

Despite the similar nomenclature, they are fundamentally different in the idea. VLES aims to represent a good compromise between accuracy and computational costs and is more similar to the URANS formulation than a LES. The idea is that the filtering width is much bigger than in LES and the unresolved part are consequently problem dependent. In practice is like an LES code that use a very coarse grid where a small (or disregardable) part of the inertial region is solved in the energy spectra.
Of course, that means that the SGS model is no longer supposed to be universal.

How can I know before the simulation if the grid is coarse o fine? If the filter is implicit how can these method be different? Is it a difference that we can do just 'a posteriori'?

[FMDenaro]

Originally Posted by lucamirtanini

How can I know before the simulation if the grid is coarse o fine? If the filter is implicit how can these method be different? Is it a difference that we can do just 'a posteriori'?

Generally, the filter width is estimated by the parameters dx+,dy+,dz+.

For example, along homogeneous directions a correct LES grid parameter would be O(20-30) while in VLES you could reach quite bigger values.


Have a look to the orgininal Speziale paper about VLES, as addressed here https://www.researchgate.net/publica...turbulent_flow