foamMeshToFluent : Error for 2D-axi simulation

AleDR · January 13, 2011, 13:17

Hi Forum!

I'm trying to have a benchmark between OpenFOAM and FLUENT with a very simple burner. It is basically constituted by a circular gas inlet and an annular air inlet which end up in a cylindrical combustion chamber.
So my problem is essentially 2D axisymmetric.

In order to have the same mesh for OF and FLUENT runs I created the (3D) grid using blockMesh and wedge shaped blocks.

First I simulate my burner using reactingFoam and then I exported my 3D grid in .msh format and verified it in FLUENT.

Reading this thread I found out that I could obtain a 2D-axisymmetric mesh from my 3D one simply importing it into GAMBIT, deleting the volume and all unnecessary surfaces and then re-exporting it in .msh format... but it doesn't work!

FLUENT can read the file, but GAMBIT doesn't.

That seems quite strange...
Do anyone know how to manage this?
Here's my .msh file.

.Alex.

[P.S.: it would be nice if fluentMeshToFoam could handle axisymmetric meshes from 2D grids..!]

mvoss · January 14, 2011, 05:27

try this one:
-make 2.5D Case by extruding in the z-dir.
-make sure the "symm"-faces are in x-y-plane
-make sure every possible node has got a pos. location in x and y
-group the front and back face e.g. "FLUID"
-name the axis faces e.g. "AXIS"

fluent3DMeshToFOAM -*.msh
makeAxialMesh -axis AXIS -wedge FLUID
collapseEdge 1e-6 180

extract the boundary.gz in ~/2/polyMesh
copy everything from 2/polyMesh to constant/polyMesh
delete 1/ and 2/

TATA!!

P.S.: i wrote myself a small script for handling all of this stuff for a multiregioncase... if somebody needs it drop a mail

AleDR · January 17, 2011, 04:29

Thank you, neewbie!

This is how I can manage to export my high-quality 2D axisymmetric mesh constructed in GAMBIT in OpenFOAM! Very useful script, I'll drop you a email right now!!!

Anyway just for this case my problem is the exact opposite: I have a mesh made up using blockMesh (so it is essentially 3D... or 2.5D as you say!) and now I'd like to transform it in a 2D mesh for FLUENT! Si ti possible??

...Anyway I have to say yours is the best option for mantaining the same node position (mesh invariance) to simulate the same case in FLUENT and OF!!

mvoss · January 17, 2011, 04:43

Quote:

Originally Posted by AleDR

I have a mesh made up using blockMesh (so it is essentially 3D... or 2.5D as you say!) and now I'd like to transform it in a 2D mesh for FLUENT!

not quiet but shure did you tried foamMeshToFluent? and i think oyu can cut of the z-Dir. with flattenMesh. never did this.

AleDR · January 17, 2011, 04:57

Yes, I tried foamMeshToFluent and now I have a .msh file which I can read and visualize in FLUENT but I can't import in GAMBIT for modifying it as a 2D..!

Mmmh, no, I didn't try flattenMesh... but as far as I know it is useful for flattening the front and back boundaries of a 2D mesh, is it??

mvoss · January 17, 2011, 05:02

sorry,... no idea about gambit. Can´t you go for symmetry in FLUENT, .... i know this isn't solving the problem.

AleDR · January 17, 2011, 06:42

...Mmmh, no, there are not such mesh manipulation features in FLUENT...
Ok, last scenario: I'll create a quasi-similar mesh in 2D using GAMBIT!

But for other cases I will use your suggestions and script:
- make the mesh in GAMBIT as 2D;
- export it in OpenFOAM making it 2.5-D;
- modifying for 2D-axysimmetric simulation.

Thank you!!!

January 13, 2011, 13:17	foamMeshToFluent : Error for 2D-axi simulation	#1
AleDR Member Alessandro Join Date: May 2009 Location: Genova Posts: 47 Rep Power: 17	Hi Forum! I'm trying to have a benchmark between OpenFOAM and FLUENT with a very simple burner. It is basically constituted by a circular gas inlet and an annular air inlet which end up in a cylindrical combustion chamber. So my problem is essentially 2D axisymmetric. In order to have the same mesh for OF and FLUENT runs I created the (3D) grid using blockMesh and wedge shaped blocks. First I simulate my burner using reactingFoam and then I exported my 3D grid in .msh format and verified it in FLUENT. Reading this thread I found out that I could obtain a 2D-axisymmetric mesh from my 3D one simply importing it into GAMBIT, deleting the volume and all unnecessary surfaces and then re-exporting it in .msh format... but it doesn't work! FLUENT can read the file, but GAMBIT doesn't. That seems quite strange... Do anyone know how to manage this? Here's my .msh file. .Alex. [P.S.: it would be nice if fluentMeshToFoam could handle axisymmetric meshes from 2D grids..!]

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January 14, 2011, 05:27		#2
mvoss Senior Member Matthias Voß Join Date: Mar 2009 Location: Berlin, Germany Posts: 449 Rep Power: 21	try this one: -make 2.5D Case by extruding in the z-dir. -make sure the "symm"-faces are in x-y-plane -make sure every possible node has got a pos. location in x and y -group the front and back face e.g. "FLUID" -name the axis faces e.g. "AXIS" fluent3DMeshToFOAM -*.msh makeAxialMesh -axis AXIS -wedge FLUID collapseEdge 1e-6 180 extract the boundary.gz in ~/2/polyMesh copy everything from 2/polyMesh to constant/polyMesh delete 1/ and 2/ TATA!! P.S.: i wrote myself a small script for handling all of this stuff for a multiregioncase... if somebody needs it drop a mail

January 17, 2011, 04:29		#3
AleDR Member Alessandro Join Date: May 2009 Location: Genova Posts: 47 Rep Power: 17	Thank you, neewbie! This is how I can manage to export my high-quality 2D axisymmetric mesh constructed in GAMBIT in OpenFOAM! Very useful script, I'll drop you a email right now!!! Anyway just for this case my problem is the exact opposite: I have a mesh made up using blockMesh (so it is essentially 3D... or 2.5D as you say!) and now I'd like to transform it in a 2D mesh for FLUENT! Si ti possible?? ...Anyway I have to say yours is the best option for mantaining the same node position (mesh invariance) to simulate the same case in FLUENT and OF!!

January 17, 2011, 04:57		#5
AleDR Member Alessandro Join Date: May 2009 Location: Genova Posts: 47 Rep Power: 17	Yes, I tried foamMeshToFluent and now I have a .msh file which I can read and visualize in FLUENT but I can't import in GAMBIT for modifying it as a 2D..! Mmmh, no, I didn't try flattenMesh... but as far as I know it is useful for flattening the front and back boundaries of a 2D mesh, is it??

January 17, 2011, 05:02		#6
mvoss Senior Member Matthias Voß Join Date: Mar 2009 Location: Berlin, Germany Posts: 449 Rep Power: 21	sorry,... no idea about gambit. Can´t you go for symmetry in FLUENT, .... i know this isn't solving the problem.

January 17, 2011, 06:42		#7
AleDR Member Alessandro Join Date: May 2009 Location: Genova Posts: 47 Rep Power: 17	...Mmmh, no, there are not such mesh manipulation features in FLUENT... Ok, last scenario: I'll create a quasi-similar mesh in 2D using GAMBIT! But for other cases I will use your suggestions and script: - make the mesh in GAMBIT as 2D; - export it in OpenFOAM making it 2.5-D; - modifying for 2D-axysimmetric simulation. Thank you!!!