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

leastSquares vs. Gauss linear

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

Like Tree5Likes
  • 3 Post By akidess
  • 1 Post By pete20r2
  • 1 Post By wildfire230

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 11, 2019, 11:10
Default leastSquares vs. Gauss linear
  #1
Senior Member
 
Join Date: Jul 2013
Posts: 124
Rep Power: 13
wildfire230 is on a distinguished road
Hi all,


Quick question: is there any general rule about when to pick leastSquares vs. Gauss linear for Grad(U)? From what I've read, it seems like leastSquares is more accurate when you have skewness in the mesh.


Thanks!
wildfire230 is offline   Reply With Quote

Old   January 11, 2019, 11:42
Default
  #2
Senior Member
 
akidess's Avatar
 
Anton Kidess
Join Date: May 2009
Location: Germany
Posts: 1,377
Rep Power: 30
akidess will become famous soon enough
Quick answer: Always use LSQ unless you run into troubles.
__________________
*On twitter @akidTwit
*Spend as much time formulating your questions as you expect people to spend on their answer.
akidess is offline   Reply With Quote

Old   January 11, 2019, 11:43
Default
  #3
Senior Member
 
Join Date: Jul 2013
Posts: 124
Rep Power: 13
wildfire230 is on a distinguished road
Great, thanks so much!
wildfire230 is offline   Reply With Quote

Old   January 11, 2019, 14:59
Default
  #4
Senior Member
 
Join Date: Jul 2013
Posts: 124
Rep Power: 13
wildfire230 is on a distinguished road
Hi, sorry one more question, does that also apply to Grad(p)?
wildfire230 is offline   Reply With Quote

Old   January 12, 2019, 09:24
Default
  #5
Senior Member
 
Peter Baskovich
Join Date: Jul 2014
Posts: 127
Rep Power: 12
pete20r2 is on a distinguished road
I've seen it recommend to use LSQ unless you're on a tet mesh because of osciillitatory behaviour. I've also seen it recommend to never apply limiters on p field and that p should use Gauss linear as it is not a convective term.
Kummi likes this.
pete20r2 is offline   Reply With Quote

Old   January 14, 2019, 08:51
Default
  #6
Senior Member
 
akidess's Avatar
 
Anton Kidess
Join Date: May 2009
Location: Germany
Posts: 1,377
Rep Power: 30
akidess will become famous soon enough
Why would it matter if the gradient you are evaluating is part of the convective term or not?
__________________
*On twitter @akidTwit
*Spend as much time formulating your questions as you expect people to spend on their answer.
akidess is offline   Reply With Quote

Old   January 14, 2019, 09:20
Default
  #7
Senior Member
 
Join Date: Jul 2013
Posts: 124
Rep Power: 13
wildfire230 is on a distinguished road
@akidess: So do you always use leastSquares for both grad(U) and grad(P)? I had one experience recently where a low-Reynolds number solution converged with grad(p) Gauss linear but diverged with grad(p) leastSquares. I guess this is probably due to a poorly designed mesh?


Thanks!
ugurtan666 likes this.
wildfire230 is offline   Reply With Quote

Old   January 14, 2019, 09:54
Default
  #8
Senior Member
 
Peter Baskovich
Join Date: Jul 2014
Posts: 127
Rep Power: 12
pete20r2 is on a distinguished road
Quote:
Originally Posted by akidess View Post
Why would it matter if the gradient you are evaluating is part of the convective term or not?
Not actually sure see:
gradient schemes
pete20r2 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
p_rgh initial residual no change with different settings manuc OpenFOAM Running, Solving & CFD 3 June 26, 2018 16:53
2nd Order Convergence Problem for 3D Airfoil turkmengokce OpenFOAM Running, Solving & CFD 1 September 10, 2015 08:20
A turbulent test case for rhoCentralFoam immortality OpenFOAM Running, Solving & CFD 13 April 20, 2014 07:32
how to modify fvScheme to converge? immortality OpenFOAM Running, Solving & CFD 15 January 16, 2013 14:06
solution diverges when linear upwind interpolation scheme is used subash OpenFOAM 0 May 29, 2010 02:23


All times are GMT -4. The time now is 04:41.