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-   -   LES explicit filtering (http://www.cfd-online.com/Forums/openfoam-solving/58567-les-explicit-filtering.html)

maka September 10, 2008 12:51

Does any body have an experien
 
Does any body have an experience of implementing explicit filtering in OpenFOAM?

I wanted to do something like Vasilyev and others 1998 JCP, "A General Class of Commutative Filters
for LES in Complex Geometries"

The difference between explicit and implicit filtering (used in OpenFOAM) is the added filtering over the non-linear term (filter(div(ui uj))) and over sub-filter model (see pp. 97 and 98). The later is treated explicitly so, I can imagine how to deal with it. The earlier does not seem that easy since its implementation will require sum_f( Sf dot (filter(rho U phi))_f ). Also, how will that affect the rest of the segregated solver since the effective flux that is used for convection is affected. Any ideas? Thanks.

Best regards,
Maka.

francesco_capuano September 11, 2012 11:18

Hi Maka,

did you manage to implement explicit filtering in OpenFOAM? I'm interested in the topic too.

Regards,
Francesco

hz283 December 26, 2012 17:35

Hi Francesco,

Do you have any clues about how to implement explicit filtering in Openfoam? I also have the same problems. Hmmm...

Happy New year!
h

Lieven December 27, 2012 06:05

Dear h,

A number of explicit filters are included in the default installation (simple, laplace and anisotropic). Have a look at the source code of one of the dynamic LES models to see how these can be used.

Also have a look at
http://www.cfd-online.com/Forums/ope...ter-codes.html
cause if you want to use the anisotropic filter would might want to include these bug fixes.

Just a side note, LES in OpenFOAM uses the implicit tophat filter at the first filter level (Delta). In this case, no explicit filtering is done, it are basically the grid and the discretization schemes that take care of the filtering. This is why you won't find LESfilter-objects in the LES models that only have one level of filtering (e.g. Smagorinsky).

Kind regards,

L

hz283 December 27, 2012 10:08

Quote:

Originally Posted by Lieven (Post 399193)
Dear h,

A number of explicit filters are included in the default installation (simple, laplace and anisotropic). Have a look at the source code of one of the dynamic LES models to see how these can be used.

Also have a look at
http://www.cfd-online.com/Forums/ope...ter-codes.html
cause if you want to use the anisotropic filter would might want to include these bug fixes.

Just a side note, LES in OpenFOAM uses the implicit tophat filter at the first filter level (Delta). In this case, no explicit filtering is done, it are basically the grid and the discretization schemes that take care of the filtering. This is why you won't find LESfilter-objects in the LES models that only have one level of filtering (e.g. Smagorinsky).

Kind regards,

L

Hi L,

Thank you so much for these suggestions. Yesterday I check the source codes for other models. They are veru helpful for me becuase I would like to introduce a dynamic model parameter for my Foam solver. Thank you.

Happy New Year!
H


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