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Showing results 1 to 22 of 22 Search took 0.00 seconds. Search: Posts Made By: alberto

Forum: OpenFOAM August 22, 2011, 19:36

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Assuming you are actually doing LES, and not... Assuming you are actually doing LES, and not under-resolved LES, your grid size should satisfy the condition on Pe' in most of the domain. This is clearly very challenging for high Reynolds numbers,...

Forum: OpenFOAM August 21, 2011, 14:11

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto It is not possible to use a purely CD scheme with... It is not possible to use a purely CD scheme with Pe > 2. In some case the problem is localised in some part of the domain, and you can try local grid refinement. If this is not the case, you can use...

Forum: OpenFOAM December 22, 2010, 15:18

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Hi Filippo (and happy holiday!), there is no... Hi Filippo (and happy holiday!), there is no dynamic Smagorinsky model for compressible flow implemented in OpenFOAM currently, just the standard Smagorinsky for compressible flows. There is the...

Forum: OpenFOAM September 3, 2010, 19:55

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Hello, Ce is not Cs. Ce is used to... Hello, Ce is not Cs. Ce is used to compute the dissipation rate. In a general geometry it is not appropriate to average along planes either. You can average locally however.

Forum: OpenFOAM August 4, 2010, 15:42

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Not really. I used it for some application in a... Not really. I used it for some application in a complex geometry and did not notice anything strange. Best,

Forum: OpenFOAM July 28, 2010, 20:16

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Hi Filippo, I think I saw part of those... Hi Filippo, I think I saw part of those results, since they were in the paper Andrea sent me. Did you try to run one case with the incompressible version of the model to see if the same...

Forum: OpenFOAM July 28, 2010, 19:53

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto I guess this returning question is a problem with... I guess this returning question is a problem with the nomenclature. The effective viscosity is nuEff = nu + nuSGS, being nu the molecular viscosity. As a consequence, clipping the effective...

Forum: OpenFOAM July 23, 2010, 10:03

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto The original Germano model was averaged along the... The original Germano model was averaged along the homogeneous direction in a channel, since such a direction exists. The model implemented in OpenFOAM obtains a single value of coefficients using...

Forum: OpenFOAM July 20, 2010, 17:52

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto There are many studies in the literature on this... There are many studies in the literature on this topic, which has been discussed already. I suggest you do a little research to find out the details. Best,

Forum: OpenFOAM July 20, 2010, 08:04

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Could you post a picture of the mesh? Is it a tet... Could you post a picture of the mesh? Is it a tet mesh or a hex mesh? The system you are showing can be meshed with blockMesh fairly easily, obtaining a fully hex mesh. I'm not sure about the more...

Forum: OpenFOAM July 19, 2010, 11:04

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto You should not clip the nuSGS, but the total... You should not clip the nuSGS, but the total viscosity. One of the features of the dynamic model is exactly that it allows backscatter, which means the nuSGS should be allowed to become negative....

Forum: OpenFOAM July 9, 2010, 09:52

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Take a look here: ... Take a look here: http://foam.sourceforge.net/doc/Doxygen/html/classFoam_1_1incompressible_1_1LESModels_1_1dynSmagorinsky.html

Forum: OpenFOAM March 25, 2010, 09:48

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto As a suggestion to save time: search the... As a suggestion to save time: search the literature, the dynamic model has been used many times and compared to others and DNS. Stanford CTR is surely a good source of information. For example ...

Forum: OpenFOAM March 25, 2010, 09:42

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto The dynamic one-equation model is not the dynamic... The dynamic one-equation model is not the dynamic Smagorinsky model. In the one-equation model you have a transport equation for the SGS turbulent kinetic energy, and the coefficients are determined...

Forum: OpenFOAM March 21, 2010, 14:57

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto I think they used QUICK because they had... I think they used QUICK because they had oscillatory behaviour from central schemes, and wanted to remove them to obtain a smooth solution. There are other strategies propose to do this (see, for...

Forum: OpenFOAM March 21, 2010, 13:04

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Those claims are extensively discussed in the... Those claims are extensively discussed in the literature, and well known to who does accurate turbulent simulations. :D Do they report a comparison with other schemes? I'll check the...

Forum: OpenFOAM March 21, 2010, 01:12

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Hi, sorry for the late reply. Send me... Hi, sorry for the late reply. Send me an email if you want my thesis. There is nothing in it about the implementation in OpenFOAM of the models however. Yes, that's correct. You could...

Forum: OpenFOAM March 19, 2010, 11:39

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto My PhD work was done in part with OpenFOAM. ... My PhD work was done in part with OpenFOAM. I'm not aware of that. To try it, you can create your own version of dynSmagorinsky, remove the global averaging and implement some strategy to...

Forum: OpenFOAM March 19, 2010, 11:01

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto It is still better than the normal Smagorinsky,... It is still better than the normal Smagorinsky, because it can adapt to the average flow conditions, meaning that if the flow globally has low-Re, the coefficient will adapt. The averaging is...

Forum: OpenFOAM March 18, 2010, 23:43

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto Pay attention to one detail. In OpenFOAM the... Pay attention to one detail. In OpenFOAM the dynamic model computes the cofficient dynamically but this is averaged on the whole domain. This is not how the original dynamic Smagorinsky model is...

Forum: OpenFOAM March 18, 2010, 12:31

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto I think it is a tradeoff between stability and... I think it is a tradeoff between stability and accuracy. In a finite volume code, your global accuracy is second order anyway. If you use higher order schemes for the convection term you can have...

Forum: OpenFOAM March 17, 2010, 21:35

Replies: 121 How to use dynSmagorinsky model correctly ? Views: 35,122 Posted By alberto QUICK is not a suitable scheme for LES, and the... QUICK is not a suitable scheme for LES, and the upwind scheme is even worse. They are too dissipative. You should use linear, or higher order central schemes. Generally, avoid limited schemes,...

Showing results 1 to 22 of 22

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