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

divScheme div(phi,U) Gauss linear behaves unexpected

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 16, 2013, 09:18
Default divScheme div(phi,U) Gauss linear behaves unexpected
  #1
New Member
 
Andreas
Join Date: Aug 2013
Posts: 8
Rep Power: 4
docinger is on a distinguished road
Hi everybody!
After reading in this awesome forum for months now, i'd like to actively post my first question today

I'm using openfoam / pimpleDyMFoam to solve incompressible flow around NACA airfoils (there'll be more details about my project in the future ...)

And i found a unexpected behaviour in the flowfields when i switch divSchemes in fvSchemes for div(phi,U) from Gauss linearUpwind grad(U) to Gauss linear

divUGausslinear.jpg

In the attached image you can see the completely "chopped" velocity field.
I use a 2D hexa mesh.

Can somebody explain to me why this happens when i use the Gauss linear scheme?

(And also can somebody tell me what the "grad(XXX)" behind the schemes is for? I seem to be incapable of finding the answer myself)

Thanks and welcome to myself,
Andreas

Last edited by docinger; August 17, 2013 at 15:44.
docinger is offline   Reply With Quote

Old   October 19, 2013, 03:56
Default
  #2
Member
 
yehanyu
Join Date: Mar 2012
Location: Beijing, China
Posts: 36
Rep Power: 5
yhy20081016 is on a distinguished road
"linear" scheme is unbounded, therefore it is usually unstable, unless the local Peclet number is less than 2. You can refer to the section titled "Divergence schemes" in "UserGuide.pdf". I suggest that you try "linearUpwind" scheme.
yhy20081016 is offline   Reply With Quote

Old   October 19, 2013, 05:15
Default
  #3
New Member
 
Andreas
Join Date: Aug 2013
Posts: 8
Rep Power: 4
docinger is on a distinguished road
yes, linearUpwind was what i started with and what I ended up using. The simulations run smooth by now and provide plausible results.

With the Peclet number dependency you mentioned, that would mean that my mesh simply is too coarse to run with linear / central differences, right?

Thanks,
A
docinger is offline   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
A turbulent test case for rhoCentralFoam immortality OpenFOAM Running, Solving & CFD 13 April 20, 2014 06:32
error on turbulence scheme immortality OpenFOAM Pre-Processing 11 August 21, 2013 08:45
no solution in second order schemes immortality OpenFOAM Running, Solving & CFD 14 May 23, 2013 01:39
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 01:23


All times are GMT -4. The time now is 09:29.