[Gmsh] Create a Boundary Layer around a blade
Javier de la Sierra
jawisr at gmail.com
Sat May 16 15:42:32 CEST 2015
Hi again,
I finally could mesh my 2D airfoil with boundary layer. I was trying to
mesh it selecting only the surfaces to apply the BL field. After selecting
also all the edges and points in surfaces boundaries it meshes is ok. I
attach the files because it could be usefull for other users (whitcomb2).
This is the result in 2D mesh.
If anyone can answer general questions about BL field I asked in my
previous message I would be really thankful because I don't understand very
well the field working.
Now, I am trying to mesh a 3D wing with a winglet but I have problems since
gmsh is not able to mesh the surfaces. I attach the files ("ala.stp" and
"ala.geo") and a image of the weird mesh.
As seen in the first picture the BL seems ok, at least in 2D.
However the rest of the mesh is not good:
I attach also the step and geo files of the wing so anyone can help me.
Thanks for your help!!
El viernes, 15 de mayo de 2015, 14:08:20 (UTC+2), Javier de la Sierra
escribió:
>
> Hi Alexander,
> I know it has been a while since your last answer, but I have to try.
> I need to create a boundary layer arround a wing imported in STEP. I try
> with Boundary Layer Field but I can't make it work. Could you make your
> boundary layer? Can you explain to me how this field works? A general
> explanation of size fields would be really helpful.
> I attach my code so you can take a look.
>
> Please take into account that my wing is shaped by surfaces 5 and 6
> (intrados and extrados). Since I want to run a 2D case the wing is placed
> between two planes.
>
> //Boundary Layer
> Field[2] = BoundaryLayer;
> Field[2].Quads = 0;
> Field[2].hfar = 1;
> Field[2].hwall_n = 1;
> Field[2].hwall_t = 2;
> Field[2].thickness = 10;
> Field[2].FacesList = {5, 6};
> Field[2].AnisoMax = 1000000;
> Field[2].IntersectMetrics = 1;
> Background Field = 2;
>
> I don't even know how big must be hwall and hfar parameters. If my chord
> is 1000 mm, how large should these parameters be if I want a 10 mm BL? I
> know boundary layer depends on y+, I just want to know if these parameters
> are mm, m or some kind of ratio.
> And finally I'd like to know how "Background Field" works. If I set my
> Boundary Layer field [2] as background, the whole mesh is refined with the
> same size (tetra). If I set another field as background, the boundary layer
> field is not noticed.
>
> Thank you very much and I hope you can help me,
>
> El domingo, 9 de febrero de 2014, 15:04:26 (UTC+1), Alexander Tismer
> escribió:
>>
>> Dear Christophe,
>>
>> many thanks for your help.
>>
>> If I try to create the layer by extrusion I get an error:
>>
>> "Impossible to extrude entity 8 (of type 306)"
>>
>> As I mentioned in the first post I create my geometry using my
>> own-written subclasses of GFace, GVertex and GEdge.
>> Is it necessary to code the extrusion-function for my own geometry entity
>> types?
>>
>> After spending some hours to the gmsh code and to the manual I figured
>> out another way. I used a BoundaryLayer field.
>>
>> Field[1] = BoundaryLayer;
>> Field[1].FacesList = {1,3,8,9};
>> Field[1].hfar = .5;
>> Field[1].hwall_n = .5;
>> Field[1].hwall_t = .5;
>> Field[1].thickness = 10.;
>> Field[1].ratio = 1.1;
>> Field[1].Quads = 0;
>> Field[1].IntersectMetrics = 1;
>> BoundaryLayer Field = 1;
>>
>> Using the mentioned field I get a mesh with a boundary layer. The mesh
>> looks nice, but if I convert it by using "gmshToFoam" and check it with
>> "checkMesh" I get some errors. The mesh fails the open boundary check.
>>
>> ***Boundary openness (-0.00152301 -0.000276836 -0.00087618) possible hole
>> in boundary description.
>> ***Open cells found, max cell openness: 1, number of open cells 21
>>
>> The boundary layer looks very fine. Please find attached two pictures.
>>
>> If I don't create a boundary layer then my mesh is ok (according to
>> checkMesh). But openfoam runs into problems with the periodic patches
>> (cyclicAMI). I figured out that it is possible to set a master surface to a
>> surface and gmsh copies the mesh from the master surface. I try to do that
>> with my own function:
>>
>> void gmshVolume::setPeriodicPairOfFaces( GModel *gm, int const
>> numFaceMaster, std::vector<int> const & EdgeListMaster,int const
>> numFaceSlave, std::vector<int> const & EdgeListSlave) const {
>>
>> int NEdges=EdgeListMaster.size();
>> GFace *gf = gm->getFaceByTag(abs(numFaceSlave));
>> gf->setMeshMaster(numFaceMaster);
>> for (int i = 0; i < NEdges; i++){
>> gf->edgeCounterparts[EdgeListSlave[i]] =
>> EdgeListMaster[i];
>> GEdge *ges = gm->getEdgeByTag(abs(EdgeListSlave[i]));
>> ges->setMeshMaster(EdgeListMaster[i]);
>> }
>> }
>>
>> Gmsh tries to mesh but ends with
>>
>> Error : Only rotations or translations can be currently taken into
>> account for periodic faces: face 2 not meshed
>>
>> Isn't it enough to set the master edges to edgeCounterparts on the slave
>> surface? Because I'm sure that my two surfaces are axially symmetric.
>>
>> Thanks
>> Alex
>>
>>
>>
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: Christophe Geuzaine [mailto:cgeu... at ulg.ac.be]
>> Gesendet: Freitag, 7. Februar 2014 19:12
>> An: Alexander Tismer
>> Cc: gm... at geuz.org
>> Betreff: Re: [Gmsh] Create a Boundary Layer around a blade
>>
>>
>> On 07 Feb 2014, at 19:10, Christophe Geuzaine <cgeu... at ulg.ac.be> wrote:
>>
>> >
>> > On 06 Feb 2014, at 10:05, Alexander Tismer <
>> alexande... at ihs.uni-stuttgart.de> wrote:
>> >
>> >> Hello,
>> >>
>> >> I try to create a boundary layer around a blade of a hydraulic turbine
>> with gmsh.
>> >>
>> >> According to the paper “Gmsh: a three-dimensional finite element mesh
>> generator with built-in pre- and post-processing facilities” (page 18-19)
>> gmsh is able to create such a layer from a set of source surfaces. For me
>> it is not really clear how to do it.
>> >> Has anybody an example geo file?
>> >> Furthermore I want to do that with my own written subclasses of GEdge,
>> GFace and GVertex using gmsh as a library. Is this also possible? Currently
>> I created a 3-d mesh of my channel using my own written classes
>> successfully. However I’m in trouble with the boundary layer creation
>> around the blade, hub and shroud.
>> >>
>> >
>> > Dear Alexander,
>> >
>> > The feature mentioned in the paper can be accessed by simply using the
>> "Extrude" command (see the attached example).
>>
>> With the attachment:
>>
>>
>> > This creates actual geometrical entities for the layer. A more
>> "classical" boundary layer mesh generator (which does not create new
>> entities, but simply extrudes a layer inside the volume) is also under
>> development, but it's not documented yet.
>> >
>> > Christophe
>> >
>> >> Any help is really appreciated.
>> >>
>> >> Many Thanks
>> >> Alex
>> >> _______________________________________________
>> >> gmsh mailing list
>> >> gm... at geuz.org
>> >> http://www.geuz.org/mailman/listinfo/gmsh
>> >
>> > --
>> > Prof. Christophe Geuzaine
>> > University of Liege, Electrical Engineering and Computer Science
>> > http://www.montefiore.ulg.ac.be/~geuzaine
>> >
>> >
>> >
>>
>> --
>> Prof. Christophe Geuzaine
>> University of Liege, Electrical Engineering and Computer Science
>> http://www.montefiore.ulg.ac.be/~geuzaine
>>
>>
>>
>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20150516/3d337aec/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: whitcomb2.geo
Type: application/octet-stream
Size: 608 bytes
Desc: not available
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20150516/3d337aec/attachment-0002.geo>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: whitcomb2.stp
Type: application/octet-stream
Size: 66762 bytes
Desc: not available
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20150516/3d337aec/attachment-0002.stp>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ala.geo
Type: application/octet-stream
Size: 818 bytes
Desc: not available
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20150516/3d337aec/attachment-0003.geo>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ala.stp
Type: application/octet-stream
Size: 1274747 bytes
Desc: not available
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20150516/3d337aec/attachment-0003.stp>