[Other] mesh comparative

Ingenieur · May 23, 2013, 10:57

Hello every one

I have a question:

I generated 2 meshs for the same case (one with Star ccm+ und the another with OpenFoam), although I sat the same refinement levels for both, I got a difference number of cells (the mesh with Starccm+ generated 28 % more cells than with Openfoam)

does any one now, where the problem is?

is there any method to generate the same number of cells??

Thanx in advance

my best regards to all

Mizo

Lieven · May 24, 2013, 09:39

Hi Monzer,

How complex is the mesh? I mean, is it simply a box or do you have object in their etc. Cause if both tools use different algorithms to handle the 'obstructions' this could easily lead to different meshes.

Cheers,

Lieven

Ingenieur · May 26, 2013, 07:43

Hi Lieven,

thank you for your reply

the mesh is a box around a car, it's nearly 100 million cells, you are right, the both tools use different algorithms to handle the mesh, but how can I get (almost) the same number of cells with the same settings(level refinement... etc)

best regards,

Mizo

Lieven · May 26, 2013, 08:17

Would importing the Star ccm+ mesh into OF solve the problem?
Cause a quick seach on google resulted in
http://openfoamwiki.net/index.php/Ccm26ToFoam
http://www.cfd-online.com/Forums/ope...-mesh-o-f.html

Then you have exactly the same number of cells ;-)

Cheers,

L

Ingenieur · May 27, 2013, 03:13

Hi Lieven,

do you know, how can I edit the shrinkDict under ($FOAM_ETC)
because the Dictionary is (read only)

best regards

Lieven · May 27, 2013, 03:31

Well, the answer is pretty straight forward. You should never edit anything under $FOAM_ETC so from that point of view it's a good thing it doesn't work ;-)

Best thing to do is to copy the file from $FOAM_ETC to the case you want to run it on.

Cheers,

Lieven

Ingenieur · May 27, 2013, 03:45

ok Lieven

I'll try it and then reply the resualt
thank you alot

Ingenieur · May 28, 2013, 03:29

Hi Lieven,

u r right, your suggestion worked very well

but I have another question about the layers.
fo u know the optimal value of (nGrow) to get a good layers everywhere??

thank you very much in advance

best regards

Lieven · May 28, 2013, 03:50

Hi Mizo,

I can't really help you with that. Maybe someone else can but then you will probably need to be more specific:
* which software package
* which geometry
* flow type
* ...

Cheers,

Lieven

Ingenieur · May 28, 2013, 04:18

Ok am using OpenFoam2.2.0

* germetry is a car
* the flow is turbulent (unsteady-les)

what I want actually is to get a good layer everywhere at the surface of the car

I tried with (nGrow=0) then (=1), the first one was pretty better

May 23, 2013, 10:57	mesh comparative	#1
Ingenieur Member Mizo Join Date: Jan 2013 Posts: 34 Rep Power: 13	Hello every one I have a question: I generated 2 meshs for the same case (one with Star ccm+ und the another with OpenFoam), although I sat the same refinement levels for both, I got a difference number of cells (the mesh with Starccm+ generated 28 % more cells than with Openfoam) does any one now, where the problem is? is there any method to generate the same number of cells?? Thanx in advance my best regards to all Mizo Last edited by Ingenieur; May 28, 2013 at 04:20.

May 26, 2013, 07:43		#3
Ingenieur Member Mizo Join Date: Jan 2013 Posts: 34 Rep Power: 13	Hi Lieven, thank you for your reply the mesh is a box around a car, it's nearly 100 million cells, you are right, the both tools use different algorithms to handle the mesh, but how can I get (almost) the same number of cells with the same settings(level refinement... etc) best regards, Mizo Last edited by Ingenieur; May 28, 2013 at 04:20.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
sliding mesh problem in CFX	Saima	CFX	46	September 11, 2021 07:38
Star CCM Overset Mesh Error (Rotating Turbine)	thezack	Siemens	7	October 12, 2016 11:14
[ICEM] surface mesh merging problem	everest	ANSYS Meshing & Geometry	44	April 14, 2016 06:41
[ICEM] Problem making structural mesh on a surface	froztbear	ANSYS Meshing & Geometry	1	November 10, 2011 08:52
[snappyHexMesh] snappyHexMesh won't work - zeros everywhere!	sc298	OpenFOAM Meshing & Mesh Conversion	2	March 27, 2011 21:11

May 24, 2013, 09:39		#2
Lieven Senior Member Lieven Join Date: Dec 2011 Location: Leuven, Belgium Posts: 299 Rep Power: 22	Hi Monzer, How complex is the mesh? I mean, is it simply a box or do you have object in their etc. Cause if both tools use different algorithms to handle the 'obstructions' this could easily lead to different meshes. Cheers, Lieven

May 26, 2013, 08:17		#4
Lieven Senior Member Lieven Join Date: Dec 2011 Location: Leuven, Belgium Posts: 299 Rep Power: 22	Would importing the Star ccm+ mesh into OF solve the problem? Cause a quick seach on google resulted in http://openfoamwiki.net/index.php/Ccm26ToFoam http://www.cfd-online.com/Forums/ope...-mesh-o-f.html Then you have exactly the same number of cells ;-) Cheers, L

May 27, 2013, 03:13		#5
Ingenieur Member Mizo Join Date: Jan 2013 Posts: 34 Rep Power: 13	Hi Lieven, do you know, how can I edit the shrinkDict under ($FOAM_ETC) because the Dictionary is (read only) best regards

May 27, 2013, 03:31		#6
Lieven Senior Member Lieven Join Date: Dec 2011 Location: Leuven, Belgium Posts: 299 Rep Power: 22	Well, the answer is pretty straight forward. You should never edit anything under $FOAM_ETC so from that point of view it's a good thing it doesn't work ;-) Best thing to do is to copy the file from $FOAM_ETC to the case you want to run it on. Cheers, Lieven

May 27, 2013, 03:45		#7
Ingenieur Member Mizo Join Date: Jan 2013 Posts: 34 Rep Power: 13	ok Lieven I'll try it and then reply the resualt thank you alot

May 28, 2013, 03:29		#8
Ingenieur Member Mizo Join Date: Jan 2013 Posts: 34 Rep Power: 13	Hi Lieven, u r right, your suggestion worked very well but I have another question about the layers. fo u know the optimal value of (nGrow) to get a good layers everywhere?? thank you very much in advance best regards

May 28, 2013, 03:50		#9
Lieven Senior Member Lieven Join Date: Dec 2011 Location: Leuven, Belgium Posts: 299 Rep Power: 22	Hi Mizo, I can't really help you with that. Maybe someone else can but then you will probably need to be more specific: * which software package * which geometry * flow type * ... Cheers, Lieven

May 28, 2013, 04:18		#10
Ingenieur Member Mizo Join Date: Jan 2013 Posts: 34 Rep Power: 13	Ok am using OpenFoam2.2.0 * germetry is a car * the flow is turbulent (unsteady-les) what I want actually is to get a good layer everywhere at the surface of the car I tried with (nGrow=0) then (=1), the first one was pretty better