CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Why unstructured meshes are not common in LES?

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree7Likes
  • 4 Post By LuckyTran
  • 2 Post By FMDenaro
  • 1 Post By sbaffini

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 19, 2021, 02:03
Default Why unstructured meshes are not common in LES?
  #1
Senior Member
 
Join Date: Jan 2018
Posts: 123
Rep Power: 6
Moreza7 is on a distinguished road
Hello,

in the most of the papers that I've read about LES, they've used structured grids for the simulation which is commonly a 2d mesh that is extruded along the spanwise direction. But in a real complex 3d geometry, it is not possible to always use a structured cubic grid and we should use unstructured polyhedral grids just like RANS or URANS.

The question is why unstructured(polyhedral) meshes are not commonly used in LES?
Moreza7 is offline   Reply With Quote

Old   February 19, 2021, 02:24
Default
  #2
Senior Member
 
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,850
Rep Power: 57
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
They are used. You are just seeing a (good) bias due to the medium you are consuming. That is, you are reading papers published in academic journals where the CFD'ers have taken extra super duper care to use nicer meshes.

In industrial CFD, it's very common to see LES done on tets and soccer-ball meshes when there is not enough time to ensure high quality grids.

Blockbuster films with >$100 production budgets are only a tiny fraction of films produced annually worldwide. But these are the ones with the greatest visibility. Few people care about B-grade films.
LuckyTran is online now   Reply With Quote

Old   February 19, 2021, 04:44
Default
  #3
Senior Member
 
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,062
Rep Power: 64
FMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura about
Yes, unstructured grid in LES are apparently not common if one searches references mainly in the journals used in accademy. However, some studies are reported since 20 years ago (K. Jansen) and reports can be found in CTR site.
Recently, some renewed interest in using FE (I mean DG approaches) cna be addressed.
Industrial applications must use prevalently unstructured grids owing to the complex geometries. But LES is still less common than other apporaches.


My opinion is that in using unstructured grids for LES there is still a theoretical lack in the understanding of the role of the implicit filter induced by the method and the consequent application of the test filtering required to use a dynamic modelling.
Moreza7 and aero_head like this.
FMDenaro is offline   Reply With Quote

Old   February 19, 2021, 08:58
Default
  #4
Senior Member
 
sbaffini's Avatar
 
Paolo Lampitella
Join Date: Mar 2009
Location: Italy
Posts: 1,809
Blog Entries: 29
Rep Power: 36
sbaffini will become famous soon enoughsbaffini will become famous soon enough
Send a message via Skype™ to sbaffini
An additional aspect, related to what Filippo mentioned, is the fact that most LES "perspectives" (which is a very broad term including numerical and theoretical aspects that would be difficult to grasp for a novice or even properly qualify here) are somehow linked to a higher (>2) order discretization of the equations, which has been historically more difficult for unstructured grids.

The renowed interest in DG methods mentioned by Filippo (and SEM, I would add), which somehow simplify achieving a higher order discretization for unstructured grids, has also leaded to a larger spread of LES computations on such grids for academic works as well.

Which brings in another possible bias: you might be focusing too much on early LES works (say, before 2010).
aero_head likes this.
sbaffini is offline   Reply With Quote

Reply

Tags
les

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
LES averaging on moving meshes loook FLUENT 2 January 29, 2020 08:06
Unstructured meshes along the border of refineMesh. Katt OpenFOAM 4 September 13, 2017 05:30
interpolation method on unstructured meshes harry Main CFD Forum 9 October 3, 2006 01:10
LES on unstructured grids, urgent!!! Lv Xin Main CFD Forum 2 September 15, 2006 23:33
Finite Volume Approach For Unstructured grid APURVA SHUKLA Main CFD Forum 2 March 15, 2001 00:14


All times are GMT -4. The time now is 03:04.