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

Gradient calculation

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 3, 2006, 23:04
Default Gradient calculation
  #1
Harry
Guest
 
Posts: n/a
To calculate 3-D gradient at centroid of a cell, which neighboring cells should be involved? To explain my question in clarity , I divide the neighboring cells of the considered cell into two groups. one group is the cell which has a common face with the considered cell. one group is the cell which only has a common line/point with the cosidered cell. Should I include both two group for gradiet calculation, Or the first group is enough. I found my code based on unstructured grids just considered the neigbouring cells with common face. Now I want to use gradient for interpolation of value at a arbitry point in a cell. I doubt the existing method of gradient calculation is not good enough.

I would appreciate your idea.

Regards,

Harry
  Reply With Quote

Old   October 7, 2006, 03:02
Default Re: Gradient calculation
  #2
Sunny
Guest
 
Posts: n/a
Hi Harry,

I have used the first group for gradient calculation, that is only the neighbors with will my cell shares common faces. Using this gradient value for interpolation, I was able to obtain good results for unstructured grids.

I dont think the value of the gradient should depend on values of cells with common edges or vertices, as you dont have any flux input through these cells.

-Sunny
  Reply With Quote

Old   October 7, 2006, 03:07
Default Re: Gradient calculation (typo)
  #3
Sunny
Guest
 
Posts: n/a
....only the neighbors with WHICH my cell shares common faces....
  Reply With Quote

Old   October 7, 2006, 04:19
Default Re: Gradient calculation (typo)
  #4
Harry
Guest
 
Posts: n/a
Thanks, Sunny. I orginally want to acquire gas properties (velocity, porosity, pressure) at an arbitary point in a cell using their gradients. I mean gradient is used for interpolation calculation, not for the solution of fluid flow.

The related results are dissapoint as this method has a bad boundedness (some value is beyong physical meaning) and accuracy, especially for big-size cell.

Now I completely give it up.
  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
conjugateHeatFoam, grid spacing and gradient calculation benk OpenFOAM 1 May 5, 2010 16:06
Face based gradient calculation Bernhard Kubicek Main CFD Forum 1 February 12, 2008 17:34
Gradient of Scalar calculation in 3D BFCskew grids james T Phoenics 0 March 28, 2007 07:12
Gradient calculation phil CFX 3 April 11, 2005 12:03
Warning 097- AB CD-adapco 6 November 15, 2004 05:41


All times are GMT -4. The time now is 21:38.