[Gmsh] Gmsh: 3D Volume with a hole (not through-going)
Omid Mahabadi
omid.mahabadi at geomechanica.com
Wed Sep 3 20:04:28 CEST 2014
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.brady at gmail.com 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 <javascript:> 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
>>> <http://www.geuz.org/mailman/listinfo/gmsh>
>>>
>>>
>>>
>>>
>>> --
>>> Oliver Willekens
>>> PhD Student
>>> 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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