[Gmsh] Ensuring conformal meshing when using geomtry from Freecad

[Benedikt Oswald]

Dear juan, thank you very much for your detailed answer!

In fact, our workflow definitely requires geometry construction in

Freecad and then meshing in gmsh; nevertheless, I

will try to debug the problem along your suggested

procedure.

thanks again and greetings, Benedikt



Am 05.04.18 um 17:22 schrieb Juan Sanchez:
> Hello Benedikt,
>
> I am using the OpenCascade factory to do the Boolean Operations in
> gmsh.  This is using the pygmsh python module to help automate the
> process:
>
> https://github.com/nschloe/pygmsh/tree/master/pygmsh
>
> The boolean operations can then be performed using code like this:
> https://github.com/nschloe/pygmsh/issues/164
>
> import pygmsh
> geom = pygmsh.opencascade.Geometry(
>   characteristic_length_min=0.1,
>   characteristic_length_max=0.1,
>   )
>
> def create_vol_volume(geom, h, w, l, x, z, cr, lcar=100):
>   f = 0.5*w
>   y = [-f,-f+cr, +f-cr, +f]
>   z = [z, z + (h-cr), z + h]
>   f = 0.5 * cr
>   points = []
>   points.append(geom.add_point((x, y[0], z[0]), lcar=lcar))
>   points.append(geom.add_point((x, y[0], z[1]), lcar=lcar))
>   points.append(geom.add_point((x, y[1], z[1]), lcar=lcar))
>   points.append(geom.add_point((x, y[1], z[2]), lcar=lcar))
>   points.append(geom.add_point((x, y[2], z[2]), lcar=lcar))
>   points.append(geom.add_point((x, y[2], z[1]), lcar=lcar))
>   points.append(geom.add_point((x, y[3], z[1]), lcar=lcar))
>   points.append(geom.add_point((x, y[3], z[0]), lcar=lcar))
>
>   lines = []
>   lines.append(geom.add_line(points[0], points[1]))
>   lines.append(geom.add_circle_arc(points[1], points[2], points[3]))
>
>   lines.append(geom.add_line(points[3], points[4]))
>   lines.append(geom.add_circle_arc(points[4], points[5], points[6]))
>   lines.append(geom.add_line(points[6], points[7]))
>   lines.append(geom.add_line(points[7], points[0]))
>
>   line_loop=geom.add_line_loop(lines)
>   surface=geom.add_plane_surface(line_loop)
>   vol = geom.extrude(surface, translation_axis=[l, 0, 0])[1]
>   return vol
>
>
> h_top=40
> corner_radius=2.5
>
> z_vol=0
> h_vol=25
> w_vol=10
> l_vol=100
> x_vol=-0.5*l_vol
> vol=create_vol_volume(geom, h=h_vol, w=w_vol, l=l_vol, x=x_vol,
> z=z_vol, cr=corner_radius)
>
> z_vol2=0
> l_vol2=50
> t_vol2=1
> w_vol2=w_vol+2*t_vol2
> h_vol2=h_vol+t_vol2
> x_vol2=x_vol + 0.5*(l_vol-l_vol2)
> vol2=create_vol_volume(geom, h=h_vol2, w=w_vol2, l=l_vol2, x=x_vol2,
> z=z_vol2, cr=corner_radius)
> vol2=geom.boolean_difference([vol2], [vol], delete_first=True,
> delete_other=False)
> geom.boolean_fragments([vol2, vol], [], delete_first=True, delete_other=False)
> print(geom.get_code())
>
>
> And then you can label the volumes as physical volumes and mesh the
> resulting geo file.
>
> Regards,
>
> Juan
>
> On Thu, Apr 5, 2018 at 5:53 AM, Benedikt Oswald
> <benedikt.oswald at lspr.swiss> wrote:
>> Dear gmsh developers
>>
>> I recently tried to mesh a geometry (made in Freecad) which consists of
>> two volumes where a smaller volume was
>>
>> subtracted in Freecad from the larger one. When I mesh the two volumes I
>> would need tetrahedra
>>
>> and that are conformal between the two volumes. Would you have a
>> suggestion on how
>>
>> to achieve this ? At the moment, gmsh does not really produce a
>> conformal mesh.
>>
>> I attach the files in question.
>>
>> Thanks a lot in advance and greetings, Benedikt
>>
>>
>>
>> ----------------------------------------------------------------------------------------------------------------------
>> Dr. sc. techn. Benedikt Oswald - first engineer - LSPR AG - phone +41 43 366 90 74
>> Grubenstrasse 9, CH-8045 Zürich, benedikt.oswald at lspr.swiss
>> ----------------------------------------------------------------------------------------------------------------------
>>
>>
>> _______________________________________________
>> gmsh mailing list
>> gmsh at onelab.info
>> http://onelab.info/mailman/listinfo/gmsh
>>
> _______________________________________________
> gmsh mailing list
> gmsh at onelab.info
> http://onelab.info/mailman/listinfo/gmsh

-- 
----------------------------------------------------------------------------------------------------------------------
Dr. sc. techn. Benedikt Oswald - first engineer - LSPR AG - phone +41 43 366 90 74
Grubenstrasse 9, CH-8045 Zürich, benedikt.oswald at lspr.swiss
----------------------------------------------------------------------------------------------------------------------


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 882 bytes
Desc: OpenPGP digital signature
URL: <http://onelab.info/pipermail/gmsh/attachments/20180406/6581c331/attachment.asc>