About LES filter

[bronise777]

I have a question. Why is only the hydro flux filtered when explicit filtering is used, but not the diffusion flux? And, are there any examples of filter here? Thanks for your answer.

[marchdf]

For a good answer I would refer you to a seminal work for explicit filtering: The use of explicit filters in large eddy simulation, T.S. Lund, Computers & Mathematics with Applications, http://linkinghub.elsevier.com/retrieve/pii/S0898122103900198, particularly bottom half of p 607.

[bronise777]

And, is this new les term obtained by explicitly filtering the original les term?

[marchdf]

Pressure is included in the hydro flux. If you believe this is a mistake and it makes a difference, feel free to change the code to suit your needs.

I am not sure what you mean by "les term".

[bronise777]

I see in LES.cpp that this SGS term is also filtered if explicit filtering is used. Is this the T’ from the above formula? The filtered SGS item is T', and the original sgs item is T. Whether my understanding is correct?
if (use_explicit_filter) {
les_filter.apply_filter(LESTerm, filtered_les_source);
LESTerm.define(
grids, dmap, NVAR, filtered_les_source.nGrow(), amrex::MFInfo(),
Factory());
amrex::MultiFab::Copy(
LESTerm, filtered_les_source, 0, 0, NVAR, filtered_les_source.nGrow());
}

[marchdf]

yes it is. Thank you for clarifying.

[bronise777]

Great! Thanks again!