[Gmsh] get mesh volume

[Juan E. Sanchez]

Hello,

Thanks for the check, and the useful script.

Upon further analysis, the circumcenter of many of the tetrahedron are 
outside their respective volumes.  This is where the additional volume 
is coming from in my calculations.

This is affecting the results of the control volume method I am using, 
since the total volume of the structure is not conserved.

Is there anything I can do to force the circumcenters to be inside of 
the tetrahedron?

Regards,

Juan


On 5/1/18 2:01 AM, Christophe Geuzaine wrote:
> 
> You can run this script, e.g. compute_volume.geo :
> 
> Merge "3dblock.msh";
> Plugin(NewView).Run;
> Plugin(ModifyComponents).Expression0 = "1";
> Plugin(ModifyComponents).Run;
> Plugin(Integrate).Dimension = 3;
> Plugin(Integrate).Run;
> 
> You'll get
> 
> Info    : Running '/Applications/Gmsh.app/Contents/MacOS/gmsh vol.geo -' 
> [Gmsh 3.0.7, 1 node, max. 1 thread]
> Info    : Started on Tue May  1 09:00:57 2018
> Info    : Reading 'vol.geo'...
> Info    : Reading '3dblock.msh'...
> Info    : 6790 vertices
> Info    : 32825 elements
> Info    : Done reading '3dblock.msh'
> Info    : Running Plugin(NewView)...
> Info    : Done running Plugin(NewView)
> Info    : Running Plugin(ModifyComponents)...
> Info    : Done running Plugin(ModifyComponents)
> Info    : Running Plugin(Integrate)...
> Info    : Step 0: integral = 1.000000000000803e-15
> Info    : Done running Plugin(Integrate)
> Info    : Done reading 'vol.geo'
> Info    : Stopped on Tue May  1 09:00:57 2018
> 
> 
> 
>> On 30 Apr 2018, at 22:58, Juan E. Sanchez <juan.e.sanchez at gmail.com 
>> <mailto:juan.e.sanchez at gmail.com>> wrote:
>>
>> Hello,
>>
>> Is there a way to get the mesh volume calculated by gmsh?
>>
>> My simulator is calculating a volume of 1.09e-15 for the attached 
>> structure, but it should be 1e-15.
>>
>> Before I added these flags
>> Mesh.OptimizeNetgen=1;
>> Mesh.OptimizeThreshold=1;
>>
>> I was getting 1.17e-15.
>>
>> I am summing the volume for each tetrahedron sub volume from the edge 
>> center, to the element center, to the centers of each triangle face of 
>> the edge.
>>
>> If my calculation is correct, are there flags I can use to improve the 
>> situation?
>>
>> I am running version 3.06.
>>
>> gmsh -3 3dblock.geo
>>
>>
>> Regards,
>>
>> Juan
>> <3dblock.geo>_______________________________________________
>> gmsh mailing list
>> gmsh at onelab.info <mailto:gmsh at onelab.info>
>> http://onelab.info/mailman/listinfo/gmsh
>