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Showing results 1 to 19 of 19 Search took 0.00 seconds. Search: Posts Made By: FMDenaro

Forum: Main CFD Forum June 21, 2017, 02:26

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro The time step in LES is taken small in order to... The time step in LES is taken small in order to resolve all temporal characteristic scales. Practically one uses a DNS time step to eliminate filtering effects in time.

Forum: Main CFD Forum June 20, 2017, 18:40

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro What you want is something like this ... What you want is something like this http://www.iaeng.org/publication/WCECS2011/WCECS2011_pp673-678.pdf However, For performing an LES, you need to specify time-dependent inflow conditions that...

Forum: Main CFD Forum June 20, 2017, 16:56

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro An analytical solution is something totally... An analytical solution is something totally different from an experimental measurement... When you have an experiment you are doing an "experimental simulation" with some boundary and initial...

Forum: Main CFD Forum June 20, 2017, 15:57

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro And that is not as same as comparing each... And that is not as same as comparing each other??? :confused:

Forum: Main CFD Forum June 20, 2017, 14:26

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro Well, I don't think that using a coarse grid and... Well, I don't think that using a coarse grid and comparing URANS and LES solutions on the same grid makes sense... Formally, you are comparing two different things...

Forum: Main CFD Forum June 20, 2017, 13:35

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro Have a look here and the references ... Have a look here and the references https://www.researchgate.net/publication/267547505_ON_URANS_SOLUTIONS_WITH_LES-LIKE_BEHAVIOUR

Forum: Main CFD Forum June 5, 2015, 03:16

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro Hello, what I wrote need some correction... ... Hello, what I wrote need some correction... 1) RANS could have a coarse grid convergence but that is for the fact that the order of magnitude of the RANS-based turbulence modelling is greater...

Forum: Main CFD Forum April 9, 2015, 17:25

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro your question is not so well-posed ... let me... your question is not so well-posed ... let me explain better, you have a flow problem to solve and you have to choose the suitable tool. Now you said to be interested in wake..that does not say...

Forum: Main CFD Forum April 9, 2015, 15:10

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro yes, generally LES grid is more computational... yes, generally LES grid is more computational extensive even for the fact that URANS could be used (depending on the problem) in 2D.

Forum: Main CFD Forum April 8, 2015, 08:41

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro Some SGS models are purely dissipative in nature... Some SGS models are purely dissipative in nature (e.g., the Smagorinsky) and could strongly affect the energy transfer of large resolved scales. Furthermore, if you have vortical structures in...

Forum: Main CFD Forum April 8, 2015, 07:03

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro the answer is...it depends! you can find very... the answer is...it depends! you can find very bad LES simulations... (too coarse grid, to dissipative model, etc) the guideline for a LES grid is to solve wall boundary by using at least 3-4...

Forum: Main CFD Forum April 8, 2015, 04:12

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro the mathematical equations looks similar but they... the mathematical equations looks similar but they differ for the expression of the unresolved terms. They take into account different unresolved tensors. URANS can be used when an external...

Forum: Main CFD Forum April 8, 2015, 03:30

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro URANS and LES provides solutions that have... URANS and LES provides solutions that have different meaning! the URANS is statistically averaged, the LES is filtered in space but not in time (if you do not use specific time-filtering apporach). ...

Forum: Main CFD Forum April 7, 2015, 17:06

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro in LES you compute statistics after a long-time... in LES you compute statistics after a long-time integration is solved and several flow fields are sampled... Difference in the statistics can be due to the grid, to the numerical model, to the SGS...

Forum: Main CFD Forum April 7, 2015, 16:47

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro for implicit-based filtering, the size is... for implicit-based filtering, the size is determined by the grid and numerical method, you can only set exactly the grid size, not the filter width...

Forum: Main CFD Forum April 7, 2015, 16:41

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro well, this is a typical effect, even simply... well, this is a typical effect, even simply porting the code on a different computer o using different compliers you see different numerical transient... However, it is really important assessing...

Forum: Main CFD Forum April 7, 2015, 15:55

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro if the filter width Delta is implicitly related... if the filter width Delta is implicitly related to the grid size h, then yes, the computational grid measure the smallest resolved scale.. However, it is possible to use an explicit filtering in...

Forum: Main CFD Forum June 15, 2014, 03:45

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro In my opinion LES and RANS equations can not be... In my opinion LES and RANS equations can not be confused, simply because the RANS equations have no time derivative by definition. Conversely URANS and LES can have a similar formulation, as a...

Forum: Main CFD Forum June 14, 2014, 04:49

Replies: 57 LES vs RANS Views: 52,720 Posted By FMDenaro Often this aspect leads to confusion... URANS and... Often this aspect leads to confusion... URANS and LES equations can be quite similar in the appearence. The key is in the way in which you model the unresolved terms: it is different. In URANS the...

Showing results 1 to 19 of 19

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