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

simplefoam convergence problem

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 13, 2012, 16:53
Default simplefoam convergence problem
  #1
New Member
 
Matt1986's Avatar
 
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 4
Matt1986 is on a distinguished road
Hi everyone,

I have a problem with my first Openfoam model.
I have modified the motorbike example, which can be found in the Openfoam-tutorials.
I have changed the bike geometry to a ball geometry and located the geometry in the center of the cavity. Blockmesh and snappyHexMesh are working fine. The simpleFoam solver is also running, but there is no convergence. How can I fix this problem.
I have tried to change the size and the parameters of the mesh whitout effect.
I am not sure, what could be changed in the the fvSolution file, without losing precision.

Looking for help
Matthias
Matt1986 is offline   Reply With Quote

Old   October 13, 2012, 22:06
Default
  #2
Senior Member
 
Awais Ali
Join Date: Feb 2010
Location: Germany
Posts: 125
Rep Power: 8
owayz is on a distinguished road
Send a message via MSN to owayz
Hi Mathias,
Can you share your fvSolution and fvSchemes file.
Boundary conditions could be the initial guess for the problem. If you can explain how and which B.Cs you are using it would be easier to help.
In my experience schemes and solver has less effect. But boundary conditions are the 'USUAL SUSPECT' in a convergence problem. Also the under-relaxation factors effect the convergence alot.
Regards,
Awais
owayz is offline   Reply With Quote

Old   October 14, 2012, 07:37
Default
  #3
New Member
 
Matt1986's Avatar
 
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 4
Matt1986 is on a distinguished road
Hi Awais,

Thank you for your answer. In the attachment you find my fvSolution and my fvSchemes files. I have haven't changed sth. in these files. They are the originals from the motorbike tutorial (incompressible simpleFoam). When I start simpleFoam the terminal tells me that no convergence criteria was found, although I have only modified the example of the tutorial.

Here are my boundary conditions:

The cavity consists of the following 6 walls and the ball:
inlet
outlet
front
back
upperwall
lowerwall
ball

inlet :
k / omega / U :type fixedValue;
value $internalField;

nut : type calculated;
value uniform 0;



p: type zeroGradient;

outlet :

k / omega / : type inletOutlet;
inletValue $internalField;
value $internalField;



U : type inletOutlet;
inletValue uniform (0 0 0);
value $internalField;



nut : type calculated;
value uniform 0;



p: type fixedValue;
value $internalField;

front back upperwall lowerwall:

k / omega / U : type slip;

nut : type calculated;
value uniform 0;



p: type slip;


ball:


k : type kqRWallFunction;
value $internalField;


omega: type omegaWallFunction;
value $internalField;
U : type fixedValue;
value uniform (0 0 0);


nut: type nutkWallFunction;
value uniform 0;


p: type zeroGradient;


Regards,

Matthias

Last edited by Matt1986; October 14, 2012 at 13:09. Reason: wrong parameters
Matt1986 is offline   Reply With Quote

Old   October 14, 2012, 07:50
Default
  #4
New Member
 
Matt1986's Avatar
 
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 4
Matt1986 is on a distinguished road
The attached Solution files
Attached Files
File Type: zip system.zip (1.1 KB, 8 views)
Matt1986 is offline   Reply With Quote

Old   October 14, 2012, 20:15
Default
  #5
Senior Member
 
Awais Ali
Join Date: Feb 2010
Location: Germany
Posts: 125
Rep Power: 8
owayz is on a distinguished road
Send a message via MSN to owayz
Hallo Mathias,
Apparently I can't find anything wrong. The only thing I could think of is Mesh. How does your mesh look like?
If you could share your mesh and transport properties file as well.
Regards,
Awais
owayz is offline   Reply With Quote

Old   October 15, 2012, 07:54
Default
  #6
New Member
 
Matt1986's Avatar
 
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 4
Matt1986 is on a distinguished road
Hi Awais,

Thank you for your help. In the Attachement you find the files and a screenshot of the mesh. The fluid flows from the right to the left side.

Regards Matthias
Attached Images
File Type: jpg Screenshot Mesh.jpg (96.9 KB, 31 views)
Attached Files
File Type: zip Mesh.zip (4.8 KB, 2 views)
Matt1986 is offline   Reply With Quote

Old   October 16, 2012, 08:32
Default
  #7
New Member
 
Matt1986's Avatar
 
Matthias K.
Join Date: Oct 2012
Location: Germany Erlangen
Posts: 20
Rep Power: 4
Matt1986 is on a distinguished road
Hi Awais,

I have checked the Mesh again and finally set the refinement level in the snappyhexmeshdict to level 3. After a clocktime of 4130 seconds the Solution has convergenzed after 871 iteration steps. Thank you very much for your hints and your support.

Regards Matthias
Attached Images
File Type: jpg screenshot.jpg (96.0 KB, 25 views)
Matt1986 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
Swirl flow convergence problem with simpleFoam iqbalsk8 OpenFOAM Running, Solving & CFD 7 November 28, 2012 01:54
Force can not converge colopolo CFX 13 October 4, 2011 22:03
convergence problem commonyue Main CFD Forum 1 December 1, 2009 04:54
Submerged fin, Convergence problem supermouniette FLUENT 10 July 6, 2009 10:47
Convergence of CFX field in FSI analysis nasdak CFX 2 June 29, 2009 01:17


All times are GMT -4. The time now is 05:06.