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

Dynamic filtering for LES

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 13, 1999, 10:10
Default Dynamic filtering for LES
  #1
Takuya TSUJI
Guest
 
Posts: n/a
I have problem with dynamic filtering procedure in LES. I know the filtering in wave space with spectral cut off filter, But How can I filter it in actual physical space? Especially in non-uniform cartesian coordinates.

Thank you.
  Reply With Quote

Old   July 14, 1999, 02:17
Default Re: Dynamic filtering for LES
  #2
Mayank Tyagi
Guest
 
Posts: n/a
Hi Takuya,

There are several filters like tophat or gaussian etc. which can be used in physical space. The question you have asked is of fundamental concern. The filtering operation on non-uniform grid does not commute with the differentiation operation, thus leading to "commutation errors" (if you are using a grid based filter whose filter width becomes function of space variables on non-uniform grids. ref: ghosal et al (1995) J. Comp. Phys.). If one does not mind second order errors i.e. commutation errors... one can write on nonuniform stencil, the physical space filter too. Obviously, that's not the solution to your problem. If one wants to reduce commutation error, there is a procedure given in Vasilyev et al (1997) (CTR annual research briefs). Again, those filters violate the "realizability requirement". Most of the researchers in LES are just ignoring "commutation errors" and pushing for high order accuracy schemes (take it with a pinch of salt!!!). Status of filtering on non-uniform grids is still in infancy stage. I'm not aware of any consistent way of grid based filtering in physical space which is realizable as well as free of commutation errors. I have more references regarding this issue, in case you are interested.

regards Mayank Tyagi
  Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Regarding Negative volume detected in Dynamic mesh Vinay Morabad FLUENT 9 April 10, 2015 23:00
Dynamic Mesh moving interface help akash.iitb FLUENT 0 August 23, 2010 23:53
Dynamic Mesh Problem. Tom Clark FLUENT 9 July 7, 2010 07:56
Dynamic mesh + grid adapt = Crash! (Files included BillH FLUENT 4 July 24, 2007 15:31
DYNAMIC FILTERING Paul Main CFD Forum 0 March 19, 2006 07:23


All times are GMT -4. The time now is 22:45.