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

Help with the discretization of the source term!

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 22, 2009, 03:32
Default Help with the discretization of the source term!
  #1
New Member
 
Libo Qian
Join Date: Sep 2009
Posts: 5
Rep Power: 16
leotsien is on a distinguished road
Now I am doing numerical research on the turbulence, using FVM and collocated grids arrangement and Low Re turbulence model. Could you tell me how to discreteize the source term for u- v- k- epslion- equation with non-uniform grids.
I've tried a lot of method, but I can't get correct solution. I don't know why?
I'am very grateful for your advice!
leotsien is offline   Reply With Quote

Old   September 22, 2009, 06:09
Default
  #2
Senior Member
 
ztdep's Avatar
 
p ding
Join Date: Mar 2009
Posts: 427
Rep Power: 19
ztdep is on a distinguished road
Send a message via Yahoo to ztdep Send a message via Skype™ to ztdep
which method did you use.
Finite volume method or finite difference method.
in the finite volume method, it is much easier.
ztdep is offline   Reply With Quote

Old   September 22, 2009, 06:18
Default
  #3
New Member
 
Libo Qian
Join Date: Sep 2009
Posts: 5
Rep Power: 16
leotsien is on a distinguished road
Quote:
Originally Posted by ztdep View Post
which method did you use.
Finite volume method or finite difference method.
in the finite volume method, it is much easier.

Finite volume method!
I don't know how to deal with the source term correctly!
With non-uniform grids
leotsien is offline   Reply With Quote

Old   September 22, 2009, 23:51
Default
  #4
Senior Member
 
ztdep's Avatar
 
p ding
Join Date: Mar 2009
Posts: 427
Rep Power: 19
ztdep is on a distinguished road
Send a message via Yahoo to ztdep Send a message via Skype™ to ztdep
Dear friends:
Since the FVM is used. the grid points are always placed at the center of the control volume.
We only need to evalue the derivative at the interface by iterpolation. we can caculate all the source term.
Could you please detail which source term trouble you.
Regards
ztdep is offline   Reply With Quote

Old   September 23, 2009, 00:19
Default
  #5
New Member
 
Libo Qian
Join Date: Sep 2009
Posts: 5
Rep Power: 16
leotsien is on a distinguished road
Quote:
Originally Posted by ztdep View Post
Dear friends:
Since the FVM is used. the grid points are always placed at the center of the control volume.
We only need to evalue the derivative at the interface by iterpolation. we can caculate all the source term.
Could you please detail which source term trouble you.
Regards
The u- and v- source term!
Actually, I've discretized the source term using FVM and coded it. But the results became divergent sudenly during iteration process. I mean in this step the results is convergent, while it will become divergent next step.
I don't know why?
Should I limit some parameters?
If so, which?
Thank you!
Long for hearing your advice.
leotsien is offline   Reply With Quote

Old   September 23, 2009, 00:29
Default
  #6
Senior Member
 
ztdep's Avatar
 
p ding
Join Date: Mar 2009
Posts: 427
Rep Power: 19
ztdep is on a distinguished road
Send a message via Yahoo to ztdep Send a message via Skype™ to ztdep
which alogirithm did you use. Have you validate your code?
If your code is correct, i think you may try to lower the realxation parameter for u and v.
BY the way, which method did you use to solve the linear algrebra equation.
ztdep is offline   Reply With Quote

Old   September 23, 2009, 01:47
Default
  #7
New Member
 
Libo Qian
Join Date: Sep 2009
Posts: 5
Rep Power: 16
leotsien is on a distinguished road
Quote:
Originally Posted by ztdep View Post
which alogirithm did you use. Have you validate your code?
If your code is correct, i think you may try to lower the realxation parameter for u and v.
BY the way, which method did you use to solve the linear algrebra equation.
SIMPLER, collocated grid, non-uniform grid
Yes, I've validated my code: lid-driven cavity flow, natural convection in square cavity and so on.
I use ADI to solve the linear algrebra equation.
If I want to simulate turbulent natural convection in a square cavity, the best relaxation factor ? Could you give me some advice?
Thank you!
leotsien is offline   Reply With Quote

Reply


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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
momentum source term zwdi FLUENT 14 June 27, 2017 15:40
DxFoam reader update hjasak OpenFOAM Post-Processing 69 April 24, 2008 01:24
DecomposePar links against liblamso0 with OpenMPI jens_klostermann OpenFOAM Bugs 11 June 28, 2007 17:51
UDFs for Scalar Eqn - Fluid/Solid HT Greg Perkins FLUENT 0 October 13, 2000 23:03
UDFs for Scalar Eqn - Fluid/Solid HT Greg Perkins FLUENT 0 October 11, 2000 03:43


All times are GMT -4. The time now is 05:13.