[Gmsh] Atypical, newbie question

Julius Bier Kirkegaard juliusbierk at gmail.com
Mon Apr 4 18:47:03 CEST 2016

```Dear all,

Thank you so much. Indeed it seems that volume embedded points would have
been ideal, but Ruth's solution with surfaces works just fine! Ruth: thank
you very, very much for taking the time to edit my code. I really
appreciate it.

And thank you for this great software!

Best wishes,
Julius

On 1 April 2016 at 09:59, Ruth Vazquez Sabariego <
ruth.sabariego at esat.kuleuven.be> wrote:

> Dear Julius,
> What you would need is to embed the points in the volume. Unfortunately,
> that is not yet implemented.
>
> From the manual:
> Point | Line { expression-list } In Surface { expression };
> Embed the point(s) or line(s) in the given surface. The surface mesh will
> conform to the mesh of the point(s) or lines(s).
> Surface { expression-list } In Volume { expression };
> Embed the surface in the given volume. The volume mesh will conform to the
> mesh of the surface.
>
>
> I’ve modified your code creating two surfaces for the points that where on
> the same plane. One point is still not embedded, thus.
> See hereafter.
>
> Note that newp, newl, newll, news give you automatically the new number
> available, that avoids taking point values generated by the Extrude
> command. Also aux[] is a list containing the generated surfaces and volume.
> aux[0] is the surface opposite to Surface{6}, aux[1] is the volume, the
> rest of aux[] contains the surrounding surfaces.
>
> Plane Surface(6) = {5};
> aux[]= Extrude {0, 0, box_size} {
>   Surface{6};
> };
> volBox = aux[1];
>
> lc=10;
> pnts[] += newp; Point(newp) = {7.150548, 1.000000,  -6.990684, lc};
> pnts[] += newp; Point(newp) = {-4.438894, 1.000000,  -8.960816, lc};
> pnts[] += newp; Point(newp) = {-9.893936, 1.000000,  1.452595, lc};
> pnts[] += newp; Point(newp) = {-1.675894, 1.000000,  9.858569, lc};
> pnts[] += newp; Point(newp) = {8.858176, 1.000000,  4.640336, lc};
>
> For k In {0:#pnts[]-1}
>  k2 = k<(#pnts[]-1)?k+1:0;
>  ln1[]+=newl; Line(newl) = {pnts[k],pnts[k2]};
> EndFor
> Line Loop(newll) = ln1[];
> surf1=news; Plane Surface(news) = newll-1;
>
> pnts2[] += newp; Point(newp) = {1.675894, 4.750000,  -9.858569, lc};
> pnts2[] += newp; Point(newp) = {-8.858176, 4.750000,  -4.640336, lc};
> pnts2[] += newp; Point(newp) = {-7.150548, 4.750000,  6.990684, lc};
> pnts2[] += newp; Point(newp) = {4.438894, 4.750000,  8.960816, lc};
> pnts2[] += newp; Point(newp) = {9.893936, 4.750000,  -1.452595, lc};
>
> For k In {0:#pnts2[]-1}
>  k2 = k<(#pnts2[]-1)?k+1:0;
>  ln2[]+=newl; Line(newl) = {pnts2[k],pnts2[k2]};
> EndFor
> Line Loop(newll) = ln2[];
> surf2=news; Plane Surface(news) = newll-1;
>
> Surface{surf1} In Volume{volBox};
> Surface{surf2} In Volume{volBox};
>
>
> // This one is not yet embedded.
> Point(newp) = {7.150548, 8.500000,  -6.990684, lc};
>
>
> HTH,
> Ruth
>
>
> —
> Prof. Ruth V. Sabariego
> KU Leuven
> Dept. Electrical Engineering ESAT/Electa, EnergyVille
> http://www.esat.kuleuven.be/electa
> http://www.energyville.be
>
> Free software: http://gmsh.info | http://getdp.info | http://onelab.info
>
>
>
>
>
>
>
> On 31 Mar 2016, at 21:33, Vincent Huber <vincent.huber at cemosis.fr> wrote:
>
> Hi Julius,
>
> I guess you have to define theses points as Physical Points, isn’t it ?
>
> All the best,
>
> VH
> ​
>
> 2016-03-31 17:54 GMT+02:00 Julius Bier Kirkegaard <juliusbierk at gmail.com>:
>
>> Dear all,
>>
>> I have (I think) a fairly simple question, but it's also quite atypical,
>> so I have had no luck Googling. I hope that you one of you might have time
>> to point me in the right direction...
>>
>> I have a box:
>>
>> box_size = 50;
>> lb = 10.;
>> Point(1) = {-box_size/2, -box_size/2, -box_size/2, lb};
>> Point(2) = {box_size/2, -box_size/2, -box_size/2, lb};
>> Point(3) = {box_size/2, box_size/2, -box_size/2, lb};
>> Point(4) = {-box_size/2, box_size/2, -box_size/2, lb};
>> Line(1) = {1, 2};
>> Line(2) = {2, 3};
>> Line(3) = {3, 4};
>> Line(4) = {4, 1};
>> Line Loop(5) = {1, 2, 3, 4};
>> Plane Surface(6) = {5};
>> Extrude {0, 0, box_size} {
>>   Surface{6};
>> }
>>
>> This works quite well and gmsh is happy to (3D) mesh it.
>>
>> The problem is that I would to ensure that certain points inside the box
>> are node points. So my question is, how do I ensure that points, like these
>>
>> lc = 10;
>> Point(5) = {7.150548, 1.000000,  -6.990684, lc};
>> Point(6) = {-4.438894, 1.000000,  -8.960816, lc};
>> Point(7) = {-9.893936, 1.000000,  1.452595, lc};
>> Point(8) = {-1.675894, 1.000000,  9.858569, lc};
>> Point(9) = {8.858176, 1.000000,  4.640336, lc};
>> Point(10) = {1.675894, 4.750000,  -9.858569, lc};
>> Point(11) = {-8.858176, 4.750000,  -4.640336, lc};
>> Point(12) = {-7.150548, 4.750000,  6.990684, lc};
>> Point(13) = {4.438894, 4.750000,  8.960816, lc};
>> Point(14) = {9.893936, 4.750000,  -1.452595, lc};
>> Point(15) = {7.150548, 8.500000,  -6.990684, lc};
>>
>> are part of the mesh nodes?
>>
>> The reason I need this is that I need to impose boundary conditions at
>> these specific points.
>>
>> Thank you all in advance.
>>
>> Best wishes,
>> Julius
>>
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>> gmsh mailing list
>> gmsh at onelab.info
>> http://onelab.info/mailman/listinfo/gmsh
>>
>>
>
>
> --
> Docteur Ingénieur de recherche
> CeMoSiS <http://www.cemosis.fr/> - vincent.huber at cemosis.fr
> Tel: +33 (0)3 68 8*5 02 06*
> IRMA - 7, rue René Descartes
> 67 000 Strasbourg
>
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