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-   -   Another LES filtering question (http://www.cfd-online.com/Forums/main/6817-another-les-filtering-question.html)

Tim November 14, 2003 08:24

Another LES filtering question
 
Hi,

If I would like to explicitly filter a variable in LES then how would I do this?

If I just apply a filter to a F-V cell centred variable I am explicitly filtering an already impicitly filtered variable. Do I have to somehow undo the implicit filter before applying an explicit filter? If so how?

Does anyone know how much the accuracy varies for a case using the same subgrid model but with differing filtering techniques?

Thanks

Tim.


Lionel Larcheveque November 21, 2003 08:54

Re: Another LES filtering question
 
Hi

I don't know way to remove implicit filtering. In fact, using explicit filter correspond to apply a filter which comes from the convolution of the explicit filter with the implicit filter. So the explicit filter has to have a lower cutoff length than the implicit filter so as to reduce the influence of the implicit one in ``total'' filtering.

For accuracy with and without explicit filtering, you may have a look at this recent article : J. Gullbrand and F. K. Chow, 2003. "The effect of numerical errors and turbulence models in large-eddy simulations of channel flow, with and without explicit filtering", J. Fluid Mech. Vol. 495, pp 323-341

Best regards

Mariafrancesca Valentino December 10, 2003 14:30

Re: Another LES filtering question
 
Hi! I'm interested in the paper you saggested; I've checked but in the 2003 there is no volume 495 for the Journal of fluid mechanincs. Are you sure that the data you gave are right? Could you check for them? I'll be very grateful to you.

Best regards Mariafracesca Valentino

you wrote:

For accuracy with and without explicit filtering, you may have a look at this recent article : J. Gullbrand and F. K. Chow, 2003. "The effect of numerical errors and turbulence models in large-eddy simulations of channel flow, with and without explicit filtering", J. Fluid Mech. Vol. 495, pp 323-3


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