[Gmsh] How to create single mesh with multiple bodies

[Christophe Geuzaine]

> On 12 Nov 2019, at 13:14, 李昊 <lihao71862b at gmail.com> wrote:
> 
> Dear all,
> 
> I use Solidworks to sketch a 3D part as shown below. In this model, there are 9 volumes.
> <image.png>
> Then I export ".step" and import into the gmsh.
> 
> Then I use Gmsh to generate 3D mesh as below:
> <image.png>
> Till now, everything looks good.
> 
> After that, I export ".mesh" to FreeFem for numerical simulation. Now something strange happens:
> I apply a force on the left side wall, and make the right side wall to be fixed.
> However, both rings does not have any displacement. That means the rings do not take part in the computation.
> <image.png>
> 
> Next, I used Boolean operation in Gmsh to merge all the nine volumes to be a single volume
> <image.png>
> This time, the result seems reasonable:
> <image.png>
> 
> 
> Please note that we hope to maintain the multiple bodies rather than a single body. Because we need to apply different physical properties for each domain.
> Therefore, is there any way to create a single mesh with multiple bodies?
> 

Yes, use BooleanFragments instead of BooleanUnion: it will preserve the internal boundaries.

Christophe



> The CAD model "auto_part_2.STEP" is attached.
> Both meshes are uploaded as well. The multiple volume one is named as "auto_part_2.mesh". The single volume one is names as "auto_part_2_1.mesh".
> 
> Please kindly check them.
> 
> Thanks very much!
> 
> 
> Best regards,
> Hao
> 
> <auto_part_2.STEP><auto_part_2_1.mesh><auto_part_2.mesh>_______________________________________________
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine