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

How to solve a single volume averaged transport equation of a porous domain

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 20, 2012, 11:45
Question How to solve a single volume averaged transport equation of a porous domain
  #1
New Member
 
Naf
Join Date: Apr 2010
Posts: 4
Rep Power: 7
AlemayehuA is on a distinguished road
Hi,

I need to define and solve a modified transport equation of additional variable (AV). The equation obtained from volume averaging of the transport equations (PDEs) in the gas phase and in solid phase of the porous domain is as shown below

a(dC/dt) + del(UC) = del(D)del(C) + R

where, a is a constant.
AlemayehuA is offline   Reply With Quote

Old   June 20, 2012, 18:31
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,828
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
You mean you want to add the "a" term in front of the transient term, but otherwise a normal transport equation? Why would you want to do this? What physical process does this model?

I would use a normal transport equation and put the modification to the transient term in a source term.
ghorrocks is offline   Reply With Quote

Old   June 20, 2012, 20:25
Wink
  #3
New Member
 
Naf
Join Date: Apr 2010
Posts: 4
Rep Power: 7
AlemayehuA is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
You mean you want to add the "a" term in front of the transient term, but otherwise a normal transport equation? Why would you want to do this? What physical process does this model?

I would use a normal transport equation and put the modification to the transient term in a source term.

Dear ghorrocks, thanks for your interest. Ya, its a normal transport equation. Its to model gas diffusion and adsorption in porous media. The equation arises after adding and simplifying the transport equations for the fluid phase and for the solid phase of the porous media.

What do you mean by putting the modification to the transient term in a source term? how do you do it? what happen to the convective and diffusive terms?
AlemayehuA is offline   Reply With Quote

Old   June 21, 2012, 06:10
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,828
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Recast your equation in the form

(dC/dt) + del(UC) = del(D)del(C) + (R-(a-1)(dC/dt))

And you can now use the normal transport equation AV, and the term (R-(a-1)(dC/dt)) becomes your source term.
ghorrocks is offline   Reply With Quote

Old   June 21, 2012, 10:30
Default
  #5
New Member
 
Naf
Join Date: Apr 2010
Posts: 4
Rep Power: 7
AlemayehuA is on a distinguished road
Thanks so much! this looks promising...then I plan to approximate the dC/dt term in the source as CEL expression given as C.Time Derivative, what do you think?
AlemayehuA is offline   Reply With Quote

Old   June 21, 2012, 11:48
Default
  #6
New Member
 
Naf
Join Date: Apr 2010
Posts: 4
Rep Power: 7
AlemayehuA is on a distinguished road
Look the error message I got,

Error detected by routine PSHDIR
CDRNAM = TIMEDERIV
CRESLT = NONE

may be not proper to try to simultaneously evaluate both the variable and its derivative
AlemayehuA is offline   Reply With Quote

Old   June 21, 2012, 18:48
Default
  #7
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,828
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
No, I do not think CEL can access time derivatives. So you need to work out how to access time derivatives. There has been some posts about this on the forum, do a search for them.
ghorrocks is offline   Reply With Quote

Reply

Tags
additional variables, gas transport equation, porous domain

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
error message cuteapathy CFX 14 March 20, 2012 07:45
Porous domain set-up from single pressure loss value siw CFX 1 December 8, 2011 17:36
BlockMesh FOAM warning gaottino OpenFOAM Native Meshers: blockMesh 7 July 19, 2010 14:11
Axisymmetrical mesh Rasmus Gjesing (Gjesing) OpenFOAM Native Meshers: blockMesh 10 April 2, 2007 14:00
Transport equation in Solid domain Gerradar CFX 3 July 15, 2005 23:07


All times are GMT -4. The time now is 20:04.