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

the calculation of gradient

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 26, 2012, 00:45
Default the calculation of gradient
  #1
Member
 
zakir
Join Date: Nov 2011
Posts: 43
Rep Power: 5
zakir hussain is on a distinguished road
hello everybody
From 10.1.1.3 Control Volume Gradients of the CFX-Sover Theory Guide ,I know that:
\nabla(\varphi)=\frac{1}{V}*\sum(\varphi\Deltan)_{ip}

where\Deltan is the outward surface vector at ip,V is the volume of the control volume.
We can use the utility name USER_GETVAR to obtain the gradient we interest.what I want to know is how it calculate the gradient.What kind of algorithm does it use?Is it as the formulation above?

I have a source term like this:
source=-\frac{1}{V}\sum(\varphi_{f}A_{f})

where\varphi_{f} is the value of the variable at the cell faces f, and A_{f} is the face area vectors


How can I implement it with fortran or something else?

Thank you very much!

zakir

Last edited by zakir hussain; March 26, 2012 at 01:21.
zakir hussain is offline   Reply With Quote

Old   March 31, 2012, 23:34
Default
  #2
Member
 
zakir
Join Date: Nov 2011
Posts: 43
Rep Power: 5
zakir hussain is on a distinguished road
hello everyone
I hope I can get help from you.
I have a source term like this:
source=-\frac{1}{V}\sum(\varphi_{f}A_{f})

where\varphi_{f} is the value of the variable at the cell faces f, and A_{f} is the face area vectors


How can I implement it with fortran or something else?

Thank you very much!

zakir
zakir hussain is offline   Reply With Quote

Old   April 1, 2012, 06:53
Default
  #3
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,665
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
What is the sum over? All the faces of the conttrol volume?

What is the purpose of the source term? I cannot see its physical significance.
ghorrocks is offline   Reply With Quote

Old   April 2, 2012, 09:33
Default
  #4
Member
 
zakir
Join Date: Nov 2011
Posts: 43
Rep Power: 5
zakir hussain is on a distinguished road
yes,the sum over represents all the faces of the control volume.Considering the conservation I should solve the divergence of phi what I use as an source term of poisson equation through Gauss's law ,like
\nabla\cdot\varphi=\frac{1}{V}\sum(\varphi_{f}A_{f})

Thank you for your help!

zakir
zakir hussain is offline   Reply With Quote

Reply

Tags
gradient

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 calculation Harry Main CFD Forum 3 October 7, 2006 04:19
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 21:54.