OpenFoam vs Fluent

Akuji · January 27, 2011, 08:07

I try to calculate a flow around building. So, I did a mesh in gambit and calculate in Fluent. After this, I load mesh in OpenFoam and try to calculate in it. I use the same boundary condition, but every time i have very big value of time step continuity error, epsilon and k.
I use a k-epsilon model in SimpleFoam.
Why Fluent calculate my problem, and OpenFoam can't?

cheng1988sjtu · January 27, 2011, 09:58

Is it a 2D model?

Can you use checkMesh in OpenFoam to see the detail of the mesh?

Maybe you've got some undefined faces...

Akuji · January 27, 2011, 10:01

Quote:

Originally Posted by cheng1988sjtu

Is it a 2D model?

Can you use checkMesh in OpenFoam to see the detail of the mesh?

Maybe you've got some undefined faces...

My Mesh is 3D. I always use checkMesh after import it from another application. Mesh is OK

mvoss · January 28, 2011, 03:47

please check for the internal fields in ~/0/epsilon,k,u and of cource for the bc.values (garbage in , garbage out... )

i think you just started with unphysical internal values. no offense, but as often is i blew up a solver run as often it was my fault because of bad initialization and fancy bc.

try to do a potentialFoam on beforehand to get an initial guess.

neewbie

amgode · January 28, 2011, 03:51

Could you please elaborate a little more on your problem.....with regards to the schemes you used in OpenFoam and also the solvers used...

Regards,

Amol

Akuji · January 31, 2011, 08:15

today I try to use a Spalar-Allmaras model, because k-eps was converged only with vary small relaxation factors.

When I look velocity, I see, that in magnitude I have only positive values, in axes y and z-positive and negative. But in X-only positive, so as I understand I haven't a vortex.
But fluent shows a lot of vortexes.

Where mistake?

alberto · February 1, 2011, 01:30

Hello,

before we can try to answer you should give us a bit more information :-)

- What solver are you using?
- Post your fvSchemes and your fvSolution dictionaries
- Post the output of checkMesh
- Describe the setup of your boundary conditions

Typically if you are forced to use very small relaxation factors, it means there is something wrong in the case setup (I would say most probably BC's).

Best,

Akuji · February 2, 2011, 07:39

Hello,

I use case simpleFoam
My fvSchemes and fvSolution

Also, output of checkMesh-in log file

And boundary Conditions are in 0.zip

January 27, 2011, 08:07	OpenFoam vs Fluent	#1
Akuji Member Arina Join Date: Oct 2009 Location: Belarus Posts: 71 Rep Power: 16	I try to calculate a flow around building. So, I did a mesh in gambit and calculate in Fluent. After this, I load mesh in OpenFoam and try to calculate in it. I use the same boundary condition, but every time i have very big value of time step continuity error, epsilon and k. I use a k-epsilon model in SimpleFoam. Why Fluent calculate my problem, and OpenFoam can't?

January 28, 2011, 03:51		#5
amgode New Member Amol Join Date: Jul 2009 Location: Limerick, Ireland Posts: 24 Blog Entries: 2 Rep Power: 16	Could you please elaborate a little more on your problem.....with regards to the schemes you used in OpenFoam and also the solvers used... Regards, Amol __________________ Amol Gode

February 1, 2011, 01:30		#7
alberto Senior Member Alberto Passalacqua Join Date: Mar 2009 Location: Ames, Iowa, United States Posts: 1,912 Rep Power: 36	Hello, before we can try to answer you should give us a bit more information :-) - What solver are you using? - Post your fvSchemes and your fvSolution dictionaries - Post the output of checkMesh - Describe the setup of your boundary conditions Typically if you are forced to use very small relaxation factors, it means there is something wrong in the case setup (I would say most probably BC's). Best, __________________ Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using.

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January 27, 2011, 09:58		#2
cheng1988sjtu Member Charlie Join Date: Dec 2010 Location: USA Posts: 85 Rep Power: 15	Is it a 2D model? Can you use checkMesh in OpenFoam to see the detail of the mesh? Maybe you've got some undefined faces...

January 28, 2011, 03:47		#4
mvoss Senior Member Matthias Voß Join Date: Mar 2009 Location: Berlin, Germany Posts: 449 Rep Power: 20	please check for the internal fields in ~/0/epsilon,k,u and of cource for the bc.values (garbage in , garbage out... ) i think you just started with unphysical internal values. no offense, but as often is i blew up a solver run as often it was my fault because of bad initialization and fancy bc. try to do a potentialFoam on beforehand to get an initial guess. neewbie

January 31, 2011, 08:15		#6
Akuji Member Arina Join Date: Oct 2009 Location: Belarus Posts: 71 Rep Power: 16	today I try to use a Spalar-Allmaras model, because k-eps was converged only with vary small relaxation factors. When I look velocity, I see, that in magnitude I have only positive values, in axes y and z-positive and negative. But in X-only positive, so as I understand I haven't a vortex. But fluent shows a lot of vortexes. Where mistake?