CFD Online Logo CFD Online URL
Home > Forums > OpenFOAM Running, Solving & CFD

Strange Result for Versteeg Testcase (2D, convection only, steady state)

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

LinkBack Thread Tools Display Modes
Old   August 16, 2011, 03:42
Question Strange Result for Versteeg Testcase (2D, convection only, steady state)
New Member
Join Date: Jun 2011
Posts: 12
Rep Power: 6
caramelo is on a distinguished road
Hi everybody,

I'm new to OpenFOAM and tried to implement a testcase from the Versteeg and Malalasekera book[1]. GoogleBooks

To solve the problem I used the scalarTransportFoam solver and set DT = 0 as it is a convection only problem. I used the boundary condition from the book except for the two outlet patches, where I used zeroGradient for phi.

The result I get are quite normal as long as I don't reach a certain number of cells. For example if my domain is 1 x 1 m and I use more than 21 cells in the x_1 and the x_2 direction the result is completely instable and has nothing to do with the analytic solution. I solved the div(phi,T) term with Gauss linear. But the solution doesn't converge either if I use QUICK or vanLeer to compute the gradient. Only upwind always give a reasonable but not really accurate solution.

Does anybody have an idea what problem is?

Thanks in advance.

caramelo is offline   Reply With Quote

Old   August 16, 2011, 14:16
Senior Member
santiagomarquezd's Avatar
Santiago Marquez Damian
Join Date: Aug 2009
Location: Santa Fe, Santa Fe, Argentina
Posts: 420
Rep Power: 15
santiagomarquezd will become famous soon enough
Can you post an sketch of the problem and BC's used?

Post-doctoral Fellow
Research Center for Computational Mechanics (CIMEC) - CONICET/FICH-UNL
T.E.: 54-342-4511594 Ext. 1005
Güemes 3450 - (3000) Santa Fe
Santa Fe - Argentina
santiagomarquezd is offline   Reply With Quote

Old   August 16, 2011, 15:45
New Member
Join Date: Jun 2011
Posts: 12
Rep Power: 6
caramelo is on a distinguished road
You can see a sketch in the GoogleBooks links i posted. I just added the whole case as an attachment. With this setting you will get a reasonable result. If you now increase the numbers of cells in the blockMeshDict, no reasonable result will be received any more.
Attached Files
File Type: gz 2D.tar.gz (18.6 KB, 6 views)
caramelo is offline   Reply With Quote

Old   August 16, 2011, 17:17
Senior Member
Laurence R. McGlashan
Join Date: Mar 2009
Posts: 370
Rep Power: 14
l_r_mcglashan will become famous soon enough
When you get finer grid cells, I think there's an issue with the Courant number for non-upwind schemes. Try changing ddtSchemes to Euler and make the endTime in controlDict something like 2; I get 'better' results with that.

I note that:

"At the first and last nodes where the diagonal intersects the boundary a value of 50 is assigned to \phi."

Might that be an issue?
Laurence R. McGlashan :: Website

Last edited by l_r_mcglashan; August 16, 2011 at 17:56.
l_r_mcglashan is offline   Reply With Quote

Old   August 17, 2011, 17:55
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,894
Rep Power: 26
alberto will become famous soon enoughalberto will become famous soon enough
It is simply a question of conditioning of the linear problem you are trying to solve. You would need under-relaxation (have to modified the code adding T.relax()) to use the code as steady state.

Alternatively, simply perform a pseudo-transient simulation, as suggested by Laurence, since the effect is the same as under-relaxing.

P.S. It is not a problem in the schemes ;-)

Alberto Passalacqua

GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as live DVD/USB, hard drive image and virtual image.
OpenQBMM - An open-source implementation of quadrature-based moment methods
alberto is offline   Reply With Quote


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
Time step dependence of convergence behavior of steady state simulations in CFX Chander Main CFD Forum 5 December 23, 2013 06:31
Constant velocity of the material Sas CFX 15 July 13, 2010 08:56
regarding steady state discrete phase calculations hajszan_gyula FLUENT 1 February 28, 2006 02:32
About the difference between steady and unsteady problems Lisa Main CFD Forum 11 July 5, 2000 14:37
Steady state formulation of turbulence ?? Jitendra Main CFD Forum 1 June 27, 2000 18:49

All times are GMT -4. The time now is 10:32.