[samiam1000]

Dear Foamers,

could you help me with this: I do have a question about the utility gmsh. I have done a very simple geometry: one cylinder inside the other one and I have created a mesh with gmsh.

It seems to be a good mesh, but when I try to convert it using gmshTo Foam, I get this error:

szampini@archimede:~/Documenti/Afros/CFDSimulations/01dielectricCylinder$ mshToFoam meshGeneration.msh 
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.3.1-262087cdf8db
Exec   : mshToFoam meshGeneration.msh
Date   : Jan 20 2015
Time   : 08:45:16
Host   : "archimede"
PID    : 25055
Case   : /home/szampini/Documenti/Afros/CFDSimulations/01dielectricCylinder
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time



--> FOAM FATAL IO ERROR: 
wrong token type - expected int, found on line 1 the word '$MeshFormat'

file: meshGeneration.msh at line 1.

    From function operator>>(Istream&, int&)
    in file primitives/ints/int/intIO.C at line 68.

FOAM exiting

szampini@archimede:~/Documenti/Afros/CFDSimulations/01dielectricCylinder$

Could you help?

Also, if I want to add patches name, could I do this with gmsh?

Thanks a lot,
Samuele

[alexeym]

Hi,

If you'd like to use gmshToFoam, use gmshToFoam, not mshToFoam as latter is Fluent mesh converter.

[samiam1000]

Yeah,

that's what I did (I wrote it wrong in the post: I'm gonna to change it!).

Anyway, I solved this cleaning up everything and doing it again.

Also, as far as the patches are concerned, how can I give them a name?

Thanks a lot,
Samuele

[alexeym]

In case of physical groups you can use strings instead of numbers, here's a fragment of the GEO file (if you start with GEO)

...
Physical Surface("bottom") = {14};
Physical Surface("top") = {16};
Physical Surface("sides") = {24, 18, 20, 22};
...

I don't know how to set string IDs in gmsh GUI, usually I edit file in external editor.

If you just have MSH file there's PhysicalNames section of the file, where you can set the names:

$PhysicalNames
4
2 1 "bottom"
2 2 "top"
2 3 "sides"
3 4 "cuboid"
$EndPhysicalNames

Second column is IDs of the physical groups.

[samiam1000]

Great,

thanks a lot!

Samuele!

PS: could you check me .geo file, letting me know if it is "nice"?

Point(1) = {0,0,0};
Point(18) = {0,0.55,0};

Point(2) = {0.0125,0,0};
Point(3) = {0,0,0.0125};
Point(4) = {-0.0125,0,0};
Point(5) = {0,0,-0.0125};

Point(6) = {0.005,0,0};
Point(7) = {0,0,0.005};
Point(8) = {-0.005,0,0};
Point(9) = {0,0,-0.005};

Point(10) = {0.0125,0.55,0};
Point(11) = {0,0.55,0.0125};
Point(12) = {-0.0125,0.55,0};
Point(13) = {0,0.55,-0.0125};

Point(14) = {0.005,0.55,0};
Point(15) = {0,0.55,0.005};
Point(16) = {-0.005,0.55,0};
Point(17) = {0,0.55,-0.005};

Circle(1) = {2,1,3};
Circle(2) = {3,1,4};
Circle(3) = {4,1,5};
Circle(4) = {5,1,2};

Circle(5) = {6,1,7};
Circle(6) = {7,1,8};
Circle(7) = {8,1,9};
Circle(8) = {9,1,6};

Circle(9) = {10,18,11};
Circle(10) = {11,18,12};
Circle(11) = {12,18,13};
Circle(12) = {13,18,10};

Circle(13) = {14,18,15};
Circle(14) = {15,18,16};
Circle(15) = {16,18,17};
Circle(16) = {17,18,14};

Line Loop(1) = {1,2,3,4};
Line Loop(2) = {5,6,7,8};
Plane Surface(1) = {1,2};

Line Loop(3) = {9,10,11,12};
Line Loop(4) = {13,14,15,16};
Plane Surface(2) = {3,4};

Physical Surface("bottom") = {1};
Physical Surface("top") = {2};

Ruled Surface(3) = {1, 3};
Ruled Surface(4) = {2, 4};
Physical Surface("innerWall") = {3};
Physical Surface("outerWall") = {4};

With this code, do I get a cylinder inside the other one, with for patches: top, bottom, innerWall and outerWall?
Now, if the geometry is fine, how can I mesh it properly?

[alexeym]

Well, you only describe two disks in your geometry. You have to connect them, define surfaces, then, using defined surfaces, define volumes. After you can add transfinite algorithm for mesh construction.

You can find compressed geo file in attachment. Also in attachment is a screenshot of the resulting mesh.

[samiam1000]

WoW: thanks a lot! Great mesh and very nice script. Thanks a lot!

Just 1 more questions: could you suggest me a pdf to learn GMSH?

Thanks a lot. Have a good day,
Samuele.

[alexeym]

Reference manual is quite nice (http://www.geuz.org/gmsh/doc/texinfo/gmsh.html), sections 3-5 & 6.3.2 are of particular interest, it is available in PDF format (http://www.geuz.org/gmsh/doc/texinfo/gmsh.pdf) if you insist on PDF