CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

perturbation in channelFoam?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 1, 2011, 16:07
Default perturbation in channelFoam?
  #1
Member
 
Charlie
Join Date: Dec 2010
Location: USA
Posts: 85
Rep Power: 15
cheng1988sjtu is on a distinguished road
I've just run the channelFoam using dynSmagorinsky model.

I just run the original case in tutorials, and found that the result seems to be more like laminar, which gives a Poiseuille flow.

Maybe that's because I didn't define a perturbation in channelFoam, in k file in 0 folder, I can see that it's uniform 0. Can I just change it to be nonzero?

Also the boundary type is fixed value of 0, can I change it to what's in RAS, i.e. kqRwallfunction?

In the attachment, the dot stand for the classic profile of turbulence. 2.5log(y+) +5.5, the solid line stand for the result without defining perturbation.

Does anyone have a similar experience? How can I set up the cse correctly to reproduce the log law? Thank you!
Attached Images
File Type: jpg meanvelocity.jpg (28.5 KB, 116 views)
cheng1988sjtu is offline   Reply With Quote

Old   February 2, 2011, 16:42
Default Know how to add perturbation!
  #2
Member
 
Charlie
Join Date: Dec 2010
Location: USA
Posts: 85
Rep Power: 15
cheng1988sjtu is on a distinguished road
Forget it, I figured out that perturbU can do that, hopefully, I can post some results after a while.
cheng1988sjtu is offline   Reply With Quote

Old   November 2, 2011, 12:58
Default
  #3
aka
New Member
 
Getnet
Join Date: Aug 2011
Location: LSU
Posts: 20
Rep Power: 14
aka is on a distinguished road
I have the same problem. My channel flow is laminar and I am getting a problem when I run LES. Do you get any idea how to get turbulent flow in your channel simulation?

Thanks

Last edited by aka; November 23, 2011 at 15:49.
aka is offline   Reply With Quote

Old   November 2, 2011, 14:29
Default
  #4
Member
 
Charlie
Join Date: Dec 2010
Location: USA
Posts: 85
Rep Power: 15
cheng1988sjtu is on a distinguished road
you could use perturbU to generate perturbations based on the laminar solution, this will make your simulation to fully turbulent faster.

Basically, the perturbation is added following a Gauss normal distribution, you can define the magnitude of the perturbation, and you may need a few tries.

you are also trying to implement LES in sediment transport? which model do you want to use?

Quote:
Originally Posted by aka View Post
I have the same problem. My channel flow is laminar and I am getting a problem when I want to apply LES for sediment transport mainly due to the diffusion part of the scalar sediment equation. Do you get any idea how to get turbulent flow in your channel simulation?

Thanks
cheng1988sjtu is offline   Reply With Quote

Old   November 2, 2011, 15:10
Default
  #5
aka
New Member
 
Getnet
Join Date: Aug 2011
Location: LSU
Posts: 20
Rep Power: 14
aka is on a distinguished road
Thanks. Yes I am trying to implement a sediment transport model.

Last edited by aka; November 23, 2011 at 15:52.
aka is offline   Reply With Quote

Old   November 2, 2011, 16:36
Default
  #6
aka
New Member
 
Getnet
Join Date: Aug 2011
Location: LSU
Posts: 20
Rep Power: 14
aka is on a distinguished road
one quick question: perturbU needs 'retau' in transport properties. Is there any thing else I have to put in the 'U' or 'k' files inside '0' folder?

Thanks
aka is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
channelFoam for a 3D pipe AlmostSurelyRob OpenFOAM 3 June 24, 2011 14:06
Generate a perturbation pranab_jha FLUENT 0 April 21, 2010 03:02
pressure perturbation Hao CFX 0 September 25, 2008 11:04
Inlet perturbation Linfeng Main CFD Forum 0 March 10, 2004 05:49
LES+initial perturbation RajaniKumar Main CFD Forum 13 December 17, 2001 15:25


All times are GMT -4. The time now is 12:31.