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

Help please - momentum source

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 16, 2005, 22:42
Default Help please - momentum source
  #1
Sheila
Guest
 
Posts: n/a
Hi everyone,

I am trying to modify the turbulent viscosity that goes into the momentum equation without effecting its value in the turbulence equation. It has been suggested by support that I should write the diffusion terms as a source term to cancel the existing terms and implement my values. For example, if I want to change the viscosity to SCALAR*vist then I should do the follwoing,

(S1U-S2U*UP)*(SCALAR - 1)

I have been trying to implement the above without any success. The solution diverges in any attempt to do so.

Has anyone done anything similar to the above or can you suggest anything else. Re-writing the turbulence as scalar does'nt work( I wasted 3 months trying it only to be told by support that it cant be done... )

Please help me solve this...

  Reply With Quote

Old   August 17, 2005, 05:46
Default Re: Help please - momentum source
  #2
Ibrahim
Guest
 
Posts: n/a
me too, I am trying to modify the turbulent viscosity in k-epsilon model , I tried an old version of Star-CD which contains Varcmu.f ( variable C_mu)soubroutine, but actually it does not work at all. I am planning to call the S.CD provider. BUt as u said it seem to be long story(-) cheers
  Reply With Quote

Old   August 22, 2005, 11:34
Default Re: Help please - momentum source
  #3
4xF
Guest
 
Posts: n/a
I think that it is dangerous to modify the source term S1U that way, because the source term should have also the contribution of the pressure gradient. Ask support to send you the expression they use for evaluating the source term due to the turbulent viscosity approximation i.e. div [ mu_t * grad (Vel) ]. They will have to take a look at the source code, but it should be feasible. Ask them for the explicit formulation. That will allow you to correct the source term in a an explicit manner (which should be stable) and disable the source term at the same time by multiplying the expression by -1 and adding it to S1U, etc...

Hope this helps...
  Reply With Quote

Old   August 28, 2005, 22:17
Default Re: Help please - momentum source
  #4
Sheila
Guest
 
Posts: n/a
Hi 4xF,

thank you for your response. Anctually we did go and see someoen at STAR about it, and, armmmm, well it seems like it was'nt an easy job... They gave some kind of 'deferred correction' interms of nodal velocity (Up) and it did'nt work

Sheila
  Reply With Quote

Old   August 30, 2005, 02:24
Default Re: Help please - momentum source
  #5
zxaar
Guest
 
Posts: n/a
Can you drop me a page's write up how you want to modify the viscosity, i do have a steady state solver, if it is possible i will hard code that in my solver and give you the exe to work on with. You might have to wait 10-15 days as i am in process of transfering code from my old solver (that has k-e and k-omega models) to new code. So if you write it up in sufficient details (what you are exactly trying to do), your problem might be solved otherwise.

my email is

zxaar@yahoo.com

  Reply With Quote

Old   August 31, 2005, 22:30
Default Re: Help please - momentum source
  #6
zxaar
Guest
 
Posts: n/a
did you get the reply email i wrote to you ????
  Reply With Quote

Reply

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
momentum source zht77 FLUENT 1 April 4, 2013 22:30
Momentum source...>>>Please Help...! sushii FLUENT 0 October 15, 2007 04:16
Momentum source Jackie CFX 0 February 16, 2003 02:16
momentum source Jackie CFX 7 January 31, 2003 02:13
Momentum source HDZ FLUENT 7 October 15, 2002 04:28


All times are GMT -4. The time now is 03:39.