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Quality assessment of LES by the subgrid viscosity ratio |
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#1 |
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Shuangqing Xu
Join Date: Jul 2013
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Hi, everybody,
Can anyone help me with the LES quality assessment by means of the subgrid viscosity ratio? I mean, is there any particular requirement about the subgrid viscosity ratio when using LES? I found little relevant information in this forum (http://www.cfd-online.com/Forums/cfx...ratio-les.html) but was still confused. |
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#2 | |
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Filippo Maria Denaro
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Quote:
Furthermore, LES can be performed with many other SGS models other than an eddy viscosity model. |
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#3 | |
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Shuangqing Xu
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I'm sorry for not telling the context. I've done a LES with the standard Smagorinsky-Lilly SGS model and was asked for the quality assessment for that. The viscosity ratio method is suggested as one of the standard methods (other methods including the fraction of resolved TKE, a two-point correlation). In the "fraction of resolved TKE" method, it's reported that a good LES should resolve at least 80% of the TKE. So I wonder if there is any similar criterion for the "viscosity ratio" method. Hope this makes the question more clear. Thank you. Shuangqingx |
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#4 | |
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Filippo Maria Denaro
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#5 |
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Alex
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If you are absolutely determined to use the SGS viscosity for the Quality assessment of a LES, here it is:
![]() The definition can be found here for example: Klein, Meyers and Geurts. Assessment of les quality measures using the error landscape approach. In: Meyers - Quality and Reliability of Large Eddy Simulations, pages 131-142. Springer Science+Business Media B.V., 2008 Having applied this to some LES, I can copy what FMDenaro said. It is useless to assess the quality of a LES so use the methods he mentioned instead. One reason might be that the coefficients in the formula are calibrated for isotropic turbulence. |
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#6 |
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Filippo Maria Denaro
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Yes, I partecipated at that conference, the full study was published here: http://people.mech.kuleuven.be/~jmey..._22_125106.pdf However, I did not suggested it as I was quite critical in using this methodology for many reasons... |
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#7 |
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Shuangqing Xu
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#8 | |
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Shuangqing Xu
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Quote:
One more question, senior. Hartmann et al (Chemical Engineering Science, 2004, 59, 2419-2432. see http://www.sciencedirect.com/science...09250904001575) have some discussions about the eddy viscosity ratio and the grid resolution of their LES (specifically in Section 5.1, the lower right quarter of page 2423). What would you comment on that? Thanks. Shuangqingx Last edited by shuangqingx; August 19, 2013 at 20:33. Reason: wrong use of @ |
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#9 | |
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Filippo Maria Denaro
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In any case, I do not agree that the capturing of the Kolmogorov scale by an LES can be assessed by the profiles of SGS viscosity. |
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#10 | |
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Shuangqing Xu
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Quote:
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#11 |
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Filippo Maria Denaro
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good
![]() I have some papers published wherein the SGS viscosity profiles were analyzed but I used the dynamic Smagorinsky and the analysis does not imply the LES assessment in terms of capturing of the Kolmogorov scale. |
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#12 |
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Shuangqing Xu
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Would you mind showing me some information about the publications to this point?
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#13 |
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Filippo Maria Denaro
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see for example
http://link.springer.com/article/10.1007%2Fs00162-010-0202-x#page-1 http://www.sciencedirect.com/science...45793012004537 |
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#14 | |
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Shuangqing Xu
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Quote:
![]() Last edited by shuangqingx; August 21, 2013 at 19:53. Reason: error |
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Tags |
les, quality assessment, subgrid viscosity ratio |
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