the calculation of gradient

zakir hussain · March 26, 2012, 00:45

hello everybody
From 10.1.1.3 Control Volume Gradients of the CFX-Sover Theory Guide ,I know that:
$\nabla$ ( $\varphi$ )= $\frac{1}{V}$ * $\sum$ ( $\varphi$ $\Delta$ n) $_{ip}$

where $\Delta$ n 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

zakir hussain · March 31, 2012, 23:34

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

ghorrocks · April 1, 2012, 06:53

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.

zakir hussain · April 2, 2012, 09:33

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

March 26, 2012, 00:45	the calculation of gradient	#1
zakir hussain Member zakir Join Date: Nov 2011 Posts: 43 Rep Power: 3	hello everybody From 10.1.1.3 Control Volume Gradients of the CFX-Sover Theory Guide ,I know that: $\nabla$ ( $\varphi$ )= $\frac{1}{V}$ * $\sum$ ( $\varphi$ $\Delta$ n) $_{ip}$ where $\Delta$ n 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.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

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 16:34
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 04:41

March 31, 2012, 23:34		#2
zakir hussain Member zakir Join Date: Nov 2011 Posts: 43 Rep Power: 3	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

April 1, 2012, 06:53		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 6,989 Rep Power: 59	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.

April 2, 2012, 09:33		#4
zakir hussain Member zakir Join Date: Nov 2011 Posts: 43 Rep Power: 3	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