CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   Main CFD Forum (http://www.cfd-online.com/Forums/main/)
-   -   Large Eddy Simulation and Isosurface (http://www.cfd-online.com/Forums/main/98699-large-eddy-simulation-isosurface.html)

 sheth March 16, 2012 11:36

Large Eddy Simulation and Isosurface

In many research papers the wake is shown with isosurface of eddy viscosity and vorticity. I wanted to know what is significance of such isosurface and what can be understood by isosurfaces of such fluid properties.

Additionally, I am confused about LES turbulence model. Actually many low reynolds number analysis employ LES, so application of LES to some problem is determined by flow reynolds number or some other flow characteristics, if yes can you please describe which ones. I have referred fluent manual and have read about turbulence models but still I need to clear up the where to apply LES.

 FMDenaro March 17, 2012 18:00

Quote:
 Originally Posted by sheth (Post 349865) In many research papers the wake is shown with isosurface of eddy viscosity and vorticity. I wanted to know what is significance of such isosurface and what can be understood by isosurfaces of such fluid properties. Additionally, I am confused about LES turbulence model. Actually many low reynolds number analysis employ LES, so application of LES to some problem is determined by flow reynolds number or some other flow characteristics, if yes can you please describe which ones. I have referred fluent manual and have read about turbulence models but still I need to clear up the where to apply LES. Thanks in advance.

I suggest to disregard Fluent manual for LES ... try reading some books, e.g. Sagaut.

Isosurface of a variable is not specific of LES, it is used in laminar as well as in DNS flows. Often one tries to get some idea of vortical structures in turbulence and uses isosurface of vorticity components or pressure... but detection of coherent structures requires much more than such a visualization

 sheth March 18, 2012 00:19

Quote:
 Originally Posted by FMDenaro (Post 350019) I suggest to disregard Fluent manual for LES ... try reading some books, e.g. Sagaut. Isosurface of a variable is not specific of LES, it is used in laminar as well as in DNS flows. Often one tries to get some idea of vortical structures in turbulence and uses isosurface of vorticity components or pressure... but detection of coherent structures requires much more than such a visualization
Thanks for your answer. I was wondering whats difference between Iso-surface of vorticity and "vortex core region" in post processing plotting.

 FMDenaro March 18, 2012 04:55

vorticity is only a dependent variable, its isosurface does not define a core of a vortex ... coherent vortical structures are defined differently and, to tell the truth, their definition is not univocal... you can find useful infos on this topic in the book of Lesieur on LES

 sheth March 19, 2012 08:22

Quote:
 Originally Posted by FMDenaro (Post 350045) vorticity is only a dependent variable, its isosurface does not define a core of a vortex ... coherent vortical structures are defined differently and, to tell the truth, their definition is not univocal... you can find useful infos on this topic in the book of Lesieur on LES
thanks mate... :)

 All times are GMT -4. The time now is 11:00.