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

2D flow over a Bump in channel

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

Reply
 
LinkBack Thread Tools Display Modes
Old   March 15, 2013, 13:31
Default 2D flow over a Bump in channel
  #1
New Member
 
Ben Graves
Join Date: Dec 2012
Posts: 18
Rep Power: 6
bgraves is on a distinguished road
Hi guys,

I am currently trying to run a validation case of flow over a 2D bump in a channel, using simplefoam with the k-omega SST turbulence model. I am having trouble getting the results to match the existing results by NASA at the following website, http://turbmodels.larc.nasa.gov/bump.html. The analysis looks like it is going to converge and then after 2 to 3 thousand iterations taking most of a day the time step continuity errors blow up .

Attached is a picture of the skin friction coefficient before the blow up, the same result occurs during the entire length of the simulation, so something is obviously really wrong, I just cannot figure out what The grid was generated by NASA so I think it is safe to say that the grid is not the problem. Attached is the zipped file, any help or suggestions would be greatly appreciated. which has the boundary conditions file and all of the system files I have used

Thanks,
-Ben
Attached Images
File Type: png Screenshot from 2013-03-15 10:56:54.png (22.5 KB, 57 views)
Attached Files
File Type: zip 2DbumpInChannel.zip (17.7 KB, 37 views)
bgraves is offline   Reply With Quote

Old   March 16, 2013, 21:23
Default
  #2
Senior Member
 
santiagomarquezd's Avatar
 
Santiago Marquez Damian
Join Date: Aug 2009
Location: Santa Fe, Santa Fe, Argentina
Posts: 430
Rep Power: 16
santiagomarquezd will become famous soon enough
I think you should contact

http://www.cfd-online.com/Forums/members/nisi.html

he was solving this kind of problems with simpleFoam.

Regards
__________________
Santiago MÁRQUEZ DAMIÁN, Ph.D.
Research Scientist
Research Center for Computational Methods (CIMEC) - CONICET/UNL
Tel: 54-342-4511594 Int. 7032
Colectora Ruta Nac. 168 / Paraje El Pozo
(3000) Santa Fe - Argentina.
http://www.cimec.org.ar
santiagomarquezd is offline   Reply With Quote

Old   March 3, 2017, 16:33
Default
  #3
New Member
 
Andrea Matiz C
Join Date: Feb 2017
Posts: 5
Rep Power: 2
andreamc is on a distinguished road
Hello
I am trying to simulate the same case. My setup is compressible solver (rhoSimpleFoam) in OF3.1 and I have succeed at running the case for the three coarsest grids provided by NASA. However for the last two (refined mesh) my simulation crashed and I can not find the problem.
I have found that the relaxation factors play an important role in the convergence so I have changed to p=0.05 and rho=0.1. This has made my simulation a little slow however I achieve more iterations with this change. I am positive the problem is not in the boundary conditions because I have succeed with the same BC in coarse grids. And I have also changed the solvers and the discretization schemes. But nothing seems to work and I do not know what else can be the problem.
The odd thing is whatever I change on the setup I just get to make 29 iterations. I really have not clue what else can be the problem, and I would really appreciate if you can help me.
Thanks in advance
andreamc is offline   Reply With Quote

Old   March 4, 2017, 02:20
Default
  #4
Member
 
piu58's Avatar
 
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 78
Rep Power: 2
piu58 is on a distinguished road
Dear Andrea,

without knowing the problem in detail:
A finer mesh requires a smaller time step too. In solvers where the time step can be set, make it smaller. Some solvers require to lower the maximal Co number. A larger relaxation factor is a third aid to (in fact) reduce the time step.
__________________
Uwe Pilz
--
Sie ahnen nicht, wieviel Poesie in der Berechnung
einer Logarithmentafel enthalten ist (Carl Friedrich Gauß)
piu58 is online now   Reply With Quote

Old   March 6, 2017, 15:26
Default
  #5
New Member
 
Andrea Matiz C
Join Date: Feb 2017
Posts: 5
Rep Power: 2
andreamc is on a distinguished road
Dear Uwe
Thank you very much for your answer but I'm using compressible steady-state solver (rhoSimpleFoam) so the time step shouldn't be a problem. As many people has suggested me that solution I've tried anyway but the problem persists and I still do not get any solution. My simulations crashes after 29 iterations no matter what I change.
Any other tip would be helpful
regards
andreamc is offline   Reply With Quote

Old   March 9, 2017, 03:20
Default
  #6
Member
 
piu58's Avatar
 
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 78
Rep Power: 2
piu58 is on a distinguished road
Are you sure that you don't have problems with the mesh? Did you try checkMesh?
__________________
Uwe Pilz
--
Sie ahnen nicht, wieviel Poesie in der Berechnung
einer Logarithmentafel enthalten ist (Carl Friedrich Gauß)
piu58 is online now   Reply With Quote

Old   March 23, 2017, 15:41
Default
  #7
New Member
 
Andrea Matiz C
Join Date: Feb 2017
Posts: 5
Rep Power: 2
andreamc is on a distinguished road
Dear Uwe

Yes I am sure about the mesh, checkMesh just failed at high aspect ratio cells around 8% of cells are with high aspect ratio. But I do not think that is the problem.
I am absolutely clueless about this problem I've tried BC, schemes, mesh and the simulation keeps crashing after 29 iterations
andreamc 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
Channel flow using InterFOAM DanM OpenFOAM Running, Solving & CFD 42 January 5, 2017 02:58
references for how to maintain a constant flow rate in turbulent channel flow amirrstg Main CFD Forum 0 October 25, 2011 03:17
Flow within a thin channel al0Vera FLUENT 0 June 15, 2009 10:20
Stabilizing turbulence equation in channel flow Biga Main CFD Forum 5 March 22, 2005 21:06
Inviscid Drag at subsonic, subcritical Mach # Axel Rohde Main CFD Forum 1 November 19, 2001 13:19


All times are GMT -4. The time now is 05:13.