[Gmsh] Block structured hex-only-3D-mesh for sequence of conical frustums
Florian Hoffmann
florian.hoffmann at inutech.de
Fri Apr 22 09:15:30 CEST 2016
Dear Felix,
thanks a lot for your efforts and detailed information.
Its a pity, but what can one do if the feature is just not supported.
Would you mind sending me the modified .geo file please ?
Thank you.
Best regards,
Florian
Am 21.04.2016 um 17:56 schrieb Felix Salazar:
>
> Hello again,
>
> I might be wrong, but unless there's an experimental Extrude feature
> that allows tapered/extrusion, I don't think it is possible. You could
> write directly to Christophe to check this, and maybe suggest the
> feature, if it's not already under development.
>
> What I did is this:
> * avoid Extrude. Commented the lines in your .GEO.
> * use a dilate on a duplicate of the original circle, setting the
> Geometry. CopyMeshMethod=1, so it is also transfinite
> * Added manually the lines, surfaces and volumes, setting them
> transfinite.
>
> I only did it with one quadrant, on the GUI. But it is probably
> possible to obtain the vertex and line numbers of the copied/dilated
> surface using a combination of the array[ ] and probably the Boundary{
> } function.
>
> I won't be as elegant as your current script, though.
>
> Good luck
>
> On Apr 21, 2016 11:12 AM, felix.a.salazar at gmail.com
> <mailto:felix.a.salazar at gmail.com> wrote:
>
> Dear Florian,
>
> That's a very nice .GEO file. Very organized. The problem is the
> dilation. When you Extrude the entities, you're assigning those
> entities mesh information. Then, you modify the geometry, it no
> longer remains connected. The lines, determined by the position of
> the vertex, looks correct. But if you show the geometrical
> surfaces, they are still the ones created with the extrusion, with
> the exception of the dilated one. Hence, when gmsh reach a surface
> whose mesh coordinates are known from the geometry, i.e. the one
> opposite to the extrusion, it finds discrepancies.
>
> I look at the documentation, and to my knowledge, there's no
> option that could easily help you. Even if you remove the Layers
> and create an unstructured mesh, just as a test, would cause
> errors, at least in my gmsh version.
>
> I'm thinking of an alternative. Let me do some test and I'll get
> back to you.
>
> Sorry for the delay. Time zones I guess...
>
> On Apr 21, 2016 4:48 AM, "Florian Hoffmann"
> <florian.hoffmann at inutech.de <mailto:florian.hoffmann at inutech.de>>
> wrote:
>
> Dear Felix,
>
> thank you very much for your quick response.
> Please find attached a simplified example highlighting my problem.
> It is a simple cylinder with an internal block structure. The
> 3D geometry is obtained by extruding several surfaces (=blocks
> for hexaeder meshing). Extrusion is done in line 161 of the
> *.geo file.
> With the variable 'withDilate' in line 186 one can switch
> on/off the dilate command I was trying to obtain the
> frustum-like outline with.
> I also attached two screenshot showing my problem when
> meshing: On the left hand side there is the cylinder (Extrude
> only) and on the right hand side one can see the conical
> frustum (Extrude+Dilate) but one can also see the problem with
> the mesh.
> If you could point me to the bits that I would have to
> change/add in order to make this work, that would be really
> really making my day.
>
> Thank you very much.
>
> Best regards,
>
> Florian
>
>
>
>
>
> Am 21.04.2016 um 06:18 schrieb Felix Salazar:
>>
>> Hello,
>>
>> I did something similar not too long ago. My geometry had a
>> basic structure, and for different cases, the angles and
>> lengths of the sections varied. Just make sure that Extrude
>> ReturnLateralEntities option is on, and check the contents of
>> the extruded array. Start with the B->C extrusion only, and
>> make sure that you're using the Layers option in the
>> extrusion, to get your structured mesh. Depending on your
>> options, you might need to explicitly recombine your elements
>> to get hexas. Could we see your .GEO file? Just from the B-B
>> surface to the extrusion? You can remove the details of the
>> A-A section, to protect IP
>>
>> On Apr 20, 2016 5:47 PM, "Florian Hoffmann"
>> <florian.hoffmann at inutech.de
>> <mailto:florian.hoffmann at inutech.de>> wrote:
>>
>> Dear all,
>>
>>
>> I would like to generate a block structured
>> hexaeder-only-3D-mesh for a geometry consisting of
>> several conical frustums. Something like this:
>>
>>
>> __________
>> \ /
>> | |
>> \ /
>> | |
>> C_| | _ C
>> \ / ^ extrude B->C
>> B _ \____/ _ B _|_
>> A _ |___| _ A
>>
>>
>> Section A-A has a non-circular cross-section, and section
>> B-B and all others above have circular cross-section. I
>> successfully created A-A and the circular cross-section
>> B-B. Both consist of several surfaces/blocks (see
>> attached picture). In my *.geo script I try to work with
>> variables. There I collect the IDs of all surfaces
>> forming the cross-section B-B (= the bottom of the first
>> conical frustum) in an array
>> (=cross_section_BB_surfaces[]). Nevertheless, when I try
>> to Extrude+Dilate these surfaces in order to build the
>> first conical frustum (=B-B -> C-C), during meshing I get
>> several errors about „Could not find extruded vertex …“ .
>> Extrusion-only of B-B to C-C (without Dilate) works fine,
>> but this would just give me a cylinder outline and it is
>> not what I want.
>> Since I need a block structured mesh and also because A-A
>> has a non-circular cross-section (see bottom plane of
>> geometry in attached picture) I would really like to make
>> use of the extrude command for creation of C-C and the
>> other frustum above.
>>
>> (1) Is there a way to make this work (without having to
>> create all frustums including their blocked structure by
>> hand) ?
>>
>> (2) If not, can anybody think of a solution for how to
>> script this in an efficient and handable way ?
>>
>>
>> Thanks a lot.
>>
>> Cheers Flo
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> Mit freundlichen Grüßen
>> --**
>> Dr.-Ing. Florian Hoffmann**
>> inuTech GmbH Phone : +49-(0)911-323843-22
>> <tel:%2B49-%280%29911-323843-22>
>> Fuerther Strasse 212 Fax :
>> +49-(0)911-323843-43 <tel:%2B49-%280%29911-323843-43>
>> 90429 Nuernberg E-Mai l
>> :florian.hoffmann at inutech.de
>> <mailto:florian.hoffmann at inutech.de>
>> Germany Internet : http://www.inutech.de
>>
>> inuTech GmbH
>> Sitz / Registered Office: Nuernberg
>> Handelsregister / Companies' Register: AG Nürnberg HRB
>> Nr. 19026
>> Geschäftsführer / Managing Director: Frank Vogel
>>
>> *****************************************************************
>> DIFFPACK - THE NEW GENERATION OF SIMULATION-SOFTWARE!
>>
>> Go to http://www.diffpack.com to read the details
>> *****************************************************************
>>
>>
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>>
>
> -- Mit freundlichen Grüßen -- Dr.-Ing. Florian Hoffmann
> inuTech GmbH Phone : +49-(0)911-323843-22
> <tel:%2B49-%280%29911-323843-22>
> Fuerther Strasse 212 Fax : +49-(0)911-323843-43
> <tel:%2B49-%280%29911-323843-43> 90429 Nuernberg E-Mai l :
> florian.hoffmann at inutech.de
> <mailto:florian.hoffmann at inutech.de> Germany Internet :
> http://www.inutech.de inuTech GmbH Sitz / Registered Office:
> Nuernberg Handelsregister / Companies' Register: AG Nürnberg
> HRB Nr. 19026 Geschäftsführer / Managing Director: Frank Vogel
> *****************************************************************
> DIFFPACK - THE NEW GENERATION OF SIMULATION-SOFTWARE! Go to
> http://www.diffpack.com to read the details
> *****************************************************************
>
--
Mit freundlichen Grüßen
--
Dr.-Ing. Florian Hoffmann
inuTech GmbH Phone : +49-(0)911-323843-22
Fuerther Strasse 212 Fax : +49-(0)911-323843-43
90429 Nuernberg E-Mai l : florian.hoffmann at inutech.de
Germany Internet : http://www.inutech.de
inuTech GmbH
Sitz / Registered Office: Nuernberg
Handelsregister / Companies' Register: AG Nürnberg HRB Nr. 19026
Geschäftsführer / Managing Director: Frank Vogel
*****************************************************************
DIFFPACK - THE NEW GENERATION OF SIMULATION-SOFTWARE!
Go to http://www.diffpack.com to read the details
*****************************************************************
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