[Gmsh] Gmsh: 3D Volume with a hole (not through-going)
erroll.brady at gmail.com
erroll.brady at gmail.com
Thu Sep 4 20:06:58 CEST 2014
Hi Omid,
Solidworks found errors when trying to import your original iges file; it
did not fix the file. The recent object was newly created in Solidworks and
exported to a STEP file. The STEP file was loaded into Gmsh where it was
3D-meshed and saved as a mesh and exported as a GEO file.
Erroll
On Wednesday, September 3, 2014 11:31:25 AM UTC-7, Omid Mahabadi wrote:
>
> Hi Errol,
> This is exactly what I wanted. Did Solidworks automatically find and
> correct the errors? Do you have any other suggestions for modifying the
> iges files?
>
> Thanks,
> Omid
>
> On 14-09-03 01:03 PM, erroll... at gmail.com <javascript:> wrote:
>
> Hi Omid,
> Try the attached Block2.zip.
>
> Erroll
>
>
> <https://lh5.googleusercontent.com/-EkE2FS91LsI/VAdJvqh3QUI/AAAAAAAAAAw/pfpGUvqDVdQ/s1600/Block2.jpg>
>
>
> On Tuesday, September 2, 2014 9:39:45 PM UTC-7, Omid Mahabadi wrote:
>>
>> Hi Errol,
>> In the version you sent me, the hole is through-going, in other words, it
>> goes through the entire depth of the cube (along z). However, my desired
>> geometry requires a hole that doesn't go through the entire depth (say it
>> has half of the depth of the exterior cube).
>>
>> Thank you,
>> Omid
>>
>>
>> On 14-09-02 06:04 PM, erroll... at gmail.com wrote:
>>
>> Hello Omid,
>> Solidworks found errors in your IGES file. Try the attached STEP, GEO and
>> MSH files.
>>
>>
>> <https://lh4.googleusercontent.com/-nxF0eT1U3qQ/VAY-5mA30KI/AAAAAAAAAAg/aQ6Sqk53Fp8/s1600/Block%2BMesh.jpg>
>>
>> Erroll
>>
>> On Tuesday, September 2, 2014 1:28:00 PM UTC-7, Omid Mahabadi wrote:
>>>
>>> Hi Oliver,
>>> Thanks for your response. I had also tried the variation that you sent
>>> me. The issue is that I don't want to have the flat surface that is
>>> interfacing the two volumes. I'd like the mesh to be continuous across that
>>> interface.
>>>
>>> Also, when following your suggestion, I still cannot get the same exact
>>> mesh as you did. Please see the attached screenshot.
>>>
>>> Is there any other thoughts on how to get the results I'm aiming for?
>>>
>>> Thank you,
>>> Omid
>>>
>>> On 14-08-28 06:34 PM, Oliver Willekens wrote:
>>>
>>> You could delete the volume of the cylinder you’ve created by means of
>>> extrusion and then delete one of the cylinder’s flat surfaces using the
>>> Delete command. However, it won’t give you what you want, because the
>>> box “holding the cylinder” will be unaware of the presence of the
>>> cylindrical hole.
>>>
>>> I tried this:
>>>
>>> Plane Surface(1) = {1, 2}; // square minus the circle
>>> out1[] = Extrude {0.0, 76.2, 0.0}{Surface{1};};
>>> Plane Surface(2) = {1};
>>> out2[] = Extrude {0.0, -76.2, 0.0} {Surface{2};};
>>>
>>> Which results in the 2D mesh you find in the attachment. Perhaps this is
>>> what you’re looking for?
>>>
>>> I also tried combining those two volumes using Compound Volume(4) =
>>> {out1[1], out2[1]};, but like you, I got GRegion Compound errors.
>>> Probably some basic restriction from triangulations I’m overlooking. This
>>> only means your 3D meshes will be clearly stopped at a flat interface about
>>> half-way through those two boxes, but you’ll still have a 3D mesh. I was
>>> hoping that the Compound Volume would make some tetras across this boundary
>>> though… But with the above lines, you’ll have a working mesh.
>>>
>>>
>>>
>>> 2014-08-28 17:08 GMT+02:00 Omid Mahabadi <omid.m... at geomechanica.com>:
>>>
>>>> Hi Christophe and Gmsh team,
>>>> I've been trying to model a simple cube with a cylindrical hole that is
>>>> NOT through-going (i.e., its depth is smaller than the depth of the cube),
>>>> as shown in the attached picture. The Extrude command doesn't seem to work
>>>> since it will extrude both surfaces (exterior and interior -- hole) at the
>>>> same time. I know I can define all the surfaces, surface loops, and volumes
>>>> manually, but is there a better way of defining something like this in
>>>> Gmsh?
>>>>
>>>> I also tried to use the Compound Volume command by first defining two
>>>> volumes from Extrude and then trying to combine them but I'm getting errors
>>>> for the Compound Volume visualization (Error: Cannot evaluate bounds on
>>>> GRegion Compound) and when I mesh the geometry, the actual shared
>>>> interfaces are still existing, although by the notion of compound from the
>>>> documentation, the internal interfaces should be neglected. Here is the
>>>> geometry file:
>>>>
>>>> // Characteristic length (==> element size)
>>>> cl_external = 25;
>>>> cl_excavation = 5;
>>>>
>>>> // External boundaries
>>>> Point(1) = {-127, 0.0, -127, cl_external};
>>>> Point(2) = {+127, 0.0, -127, cl_external};
>>>> Point(3) = {+127, 0.0, +127, cl_external};
>>>> Point(4) = {-127, 0.0, +127, cl_external};
>>>> Line(1) = {1, 2};
>>>> Line(2) = {2, 3};
>>>> Line(3) = {3, 4};
>>>> Line(4) = {4, 1};
>>>> Line Loop(1) = {1, 2, 3, 4};
>>>>
>>>> // Excavation boundaries
>>>> Point(5) = {0.0, 0.0, 0.0, cl_excavation};
>>>> Point(6) = {19.05, 0.0, 0.0, cl_excavation};
>>>> Point(7) = {0.0, 0.0, 19.05, cl_excavation};
>>>> Point(8) = {-19.05, 0.0, 0.0, cl_excavation};
>>>> Point(9) = {0.0, 0.0, -19.05, cl_excavation};
>>>> Circle(5) = {6, 5, 7};
>>>> Circle(6) = {7, 5, 8};
>>>> Circle(7) = {8, 5, 9};
>>>> Circle(8) = {9, 5, 6};
>>>> Line Loop(2) = {5, 6, 7, 8};
>>>>
>>>> //Using compound volumes
>>>> Plane Surface(1) = {1};
>>>> out1[] = Extrude {0.0, 76.2, 0.0}{Surface{1};};
>>>>
>>>> Plane Surface(2) = {1};
>>>> out2[] = Extrude {0.0, -76.2, 0.0}{Surface{2};};
>>>>
>>>> Compound Volume(3) = {1, 2};
>>>>
>>>>
>>>> I also tried to create the geometry in CAD software and imported it as
>>>> iges, brep or step formats but for reason the hole is not there completely.
>>>> See for instances the iges file attached.
>>>>
>>>> Can you kindly shed some light here? Am I doing something wrong? Or are
>>>> there Gmsh tricks/commands that I can use to achieve my goal?
>>>>
>>>> Thank you,
>>>> Omid
>>>>
>>>> --
>>>> Omid Mahabadi, Ph.D.
>>>> Geomechanica, Inc.http://www.geomechanica.com/
>>>> Tel : +1-647-478-9767
>>>> Cell: +1-416-824-2408
>>>>
>>>>
>>>> _______________________________________________
>>>> gmsh mailing list
>>>> gm... at geuz.org
>>>> http://www.geuz.org/mailman/listinfo/gmsh
>>>>
>>>>
>>>
>>>
>>> --
>>> Oliver Willekens
>>> PhD Student
>>> [image: LCP group logo] <https://lcp.elis.ugent.be/>
>>>
>>> Liquid Crystals & Photonics Group
>>> Sint- Pietersnieuwstraat 41
>>> 9000 Gent
>>> Phone: +32 9 264.89.51
>>>
>>>
>>> --
>>> Omid Mahabadi, Ph.D.
>>> Geomechanica, Inc.http://www.geomechanica.com/
>>> Tel : +1-647-478-9767
>>> Cell: +1-416-824-2408
>>>
>>>
>> --
>> Omid Mahabadi, Ph.D.
>> Geomechanica, Inc.http://www.geomechanica.com/
>> Tel : +1-647-478-9767
>> Cell: +1-416-824-2408
>>
>>
> --
> Omid Mahabadi, Ph.D.
> Geomechanica, Inc.http://www.geomechanica.com/
> Tel : +1-647-478-9767
> Cell: +1-416-824-2408
>
>
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