[Gmsh] How to select Pre/Post processing entity by location?

[Shamsul Arefin]

Hi Andrew,

Thanks for the link ... 

I want to do the 'naming task' in the batch. Problem is, after the generation of the volume, the surface IDs are created randomly. In GUI this is not a problem,  but since I am in batch mode, i need a rather stable solution to do this generation and naming repeatedly. 



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Regards,
Shamsul Arefin
ph: 017655441319
On Wed 13 Dec 6:53:50 pm, andrew <armitatz at gmail.com> wrote:
I am glad it helped a bit.

For extrusion hints you can see the tutorial of openfoam and gmsh
https://openfoamwiki.net/index.php/2D_Mesh_Tutorial_using_GMSH [https://openfoamwiki.net/index.php/2D_Mesh_Tutorial_using_GMSH]
It gives some info for the extrusion vectors.

If you change the function in my files you can create functions for a few elementary geometrical entities. Unfortunately selecting elements according to geometry is a bit tricky in gmsh.
You can get the elements in an array and sweep in the array. This way you can select the elements according to their coordinates with any criteria you like.

For example in my file it goes

For PlaneFilter_jj In {0:#PlaneFilter_Surfaces[]-1} <------- SWEEP SURFACES
PlaneFilter_n[]=PointsOf{Surface{PlaneFilter_Surfaces[PlaneFilter_jj]};}; <----------- GET ALL POINTS OF SURFACE
PlaneFilter_nn=#PlaneFilter_n[];
PlaneFilter_cc=0;
For PlaneFilter_kk In {0:#PlaneFilter_n[]-1} <--------- SWEEP POINTS IN SURFACE
PlaneFilter_pn[]=Point{PlaneFilter_n[PlaneFilter_kk]};
PlaneFilter_px=PlaneFilter_pn[0]; <------- COORDINATES
PlaneFilter_py=PlaneFilter_pn[1];
PlaneFilter_pz=PlaneFilter_pn[2];
.......

the two nested loops are for getting the points and their coordinates. After that you can filter them any way you like...




2017-12-13 16:40 GMT+02:00 Shamsul Arefin <mail.shanto at gmail.com [mailto:mail.shanto at gmail.com]>:

This is a nice trick. Thanks Andrew.

However, this is only for selecting plane surfaces. I may have to tweak the code for Cylindrical Surfaces and also for more control over the shape of the geometry.

# It would have been better if I could know how entities are stored in an array. Say I extrude a surface to create a block. If this extrusion command is saved in an array, what would be the sequence of IDs in the array, of generated surfaces of the block.

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Regards,
Shamsul Arefin
ph: 017655441319
On Tue 12 Dec 3:46:59 pm, andrew <armitatz at gmail.com [mailto:armitatz at gmail.com]> wrote:
I thought it was together with the other files !



2017-12-12 11:43 GMT+02:00 Shamsul Arefin <mail.shanto at gmail.com [mailto:mail.shanto at gmail.com]>:

Is there no other selection by location option? Say I want to select the areas at 'z=0', or volumes between -10<x<+10 and -10<y<+10.

The purpose is to select nodes from a particular geometric entity and define name for those nodes i.e. a nodal set.

Usually when I know the ID of a surface (for example), i can define a "physical surface" and get the nodes and elements in the output-file grouped together. Problem is, I would not know surface ID's while working in the batch.


Or anyone has a better idea for doing this with gmsh?


​
Regards,
Shamsul Arefin
ph: 017655441319
On Mon 11 Dec 8:26:36 pm, andrew <armitatz at gmail.com [mailto:armitatz at gmail.com]> wrote:
​perhaps this could help you. It selects a face that belongs to a plane

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2017-12-11 18:28 GMT+02:00 Shamsul Arefin <mail.shanto at gmail.com [mailto:mail.shanto at gmail.com]>:

Hello,

Lets say I have a box modeled in gmsh. I want to select different faces of the box just by - selection through location coordinate. So far have not find anything in the documentation! Can anyone help?


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Regards,
Shamsul Arefin
ph: 017655441319

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