[Gmsh] Some questions on tutorial 5
Christophe Geuzaine
cgeuzaine at ulg.ac.be
Fri Apr 3 15:57:54 CEST 2009
dolfyn wrote:
> Dear all,
>
> Still learning all about Gmsh.
>
> Tutorial t1, t2, t3 (two versions; one with prisms, one with
> tetrahedra), t4 (beautiful prism/hex example) run.
>
> (btw there seems to be a difference in the t3-postprocessing: in the
> tet-version all the velocity vectors show up, in the prism-version
> only at the model surfaces).
>
> Tutorial 5 was slightly adapted because 'physical volume'
> and 'physical surfaces' names are important. The changes:
>
> lcar2 = .05; (just a bit different)
> lcar3 = .02;
>
> In the function after "Surface Loop(theloops[t]) = ":
>
> Physical Surface(Sprintf("Sphere_%g",t)) = theloops[t];
>
Hi Henk - This physical surface definition is wrong: "theloops[t]"
contains the id number of a "surface loop", not a "surface".
You should use the list of surface ids instead the surface loop id to
define the physical entity.
Keep up the good the work with Dolphyn!
Christophe
> In the For-loop delete/switch off:
>
> // Physical Volume (t) = thehole ; (do not want the holes)
>
> And finally instead of "Physical Volume (10) = 186 ;":
>
> Physical Volume ("Fluid") = 186 ;
> Physical Surface("Floor") = {27};
> Physical Surface("Wall_1") = {29};
> Physical Surface("Wall_2") = {31};
> Physical Surface("Wall_3") = {33};
> Physical Surface("Wall_4") = {37};
> Physical Surface("Roof") = {35};
> Physical Surface("Box") = {25,39,23};
>
> The status of the workflow so far:
>
> $ gmsh t5.geo (hit mesh 3d and save mesh)
> $ mv t5.msh t5d.msh (important renaming)
> $ gmsh2dolfyn
> t5d (creates dolfyn geom. files and t5d.inp)
> $ cat t5d.inp
> rname,7,Floor
> rname,8,Wall_1
> rname,9,Wall_2
> rname,10,Wall_3
> rname,11,Wall_4
> rname,12,Roof
> rname,13,Box
> $ ../../../solver/vs0500/preprocessor
> t5d
> 1.0 (creates t5d.geo, the reason to rename!)
> bin
> $ ../../../solver/vs0500/dolfyn
> t5d
> $ gmsh t5d.msh
> $
>
> the result is shown in the figure.
>
> HOWEVER there is 1 small glitch... the saved file of gmsh shows:
>
> $ more t5.msh
> $MeshFormat
> 2 0 8
> $EndMeshFormat
> $PhysicalNames
> 13
> 1 "Sphere_1"
> 2 "Sphere_2"
> 3 "Sphere_3"
> 4 "Sphere_4"
> 5 "Sphere_5"
> 6 "Fluid"
> 7 "Floor"
> 8 "Wall_1"
> 9 "Wall_2"
> 10 "Wall_3"
> 11 "Wall_4"
> 12 "Roof"
> 13 "Box"
> $EndPhysicalNames
> $Nodes
> 4955
> 1 0.5 0.5 0.5
> ...
>
> So the Sphere surfaces are there; named correctly. But in
> the 'element' section they do not show up (and dolfyn puts them in
> the 'default surface' 0). And because gmsh2dolfyn does not find the
> five Sphere surfaces in the msh file they are not exported.
>
> A beautiful aspect of this workflow is that one can use
> the 'physical surface' names in the control file for dolfyn as
> well:
>
> ...
>
> thermal on
> gravity 0 0 -9.81
>
> post t cell
> post t vert
>
> set T0 273.0
>
> # safety first
> boundary,0
> wall
> noslip
> 0.0 0.0 0.0
> fixed
> $T0 + 50 0.0
>
> boundary,floor
> wall
> noslip
> 0.0 0.0 0.0
> fixed
> $T0 + 20 0.0
>
> boundary,wall_1
> wall
> noslip
> 0.0 0.0 0.0
> fixed
> $T0 + 20 0.0
>
> ...
>
> The two questions:
> 1) where are the Sphere_i surfaces gone in the msh file?
> 2) I finally went for:
>
> Physical Surface(Sprintf("Sphere_%g",t)) = theloops[t];
>
> Other constructs like using a string array
>
> Names[] = "s1","s2","s3" ;
>
> or before 'Call CheeseHole'
>
> s = Sprintf(s,"Sphere_%g",t);
> Physical Surface(s);
>
> Do not work.
>
> What am I missing here?
>
> Thanks in advance!
> Henk
>
> ps: enjoying gmsh! and I guess that some users will enjoy the
> combination of gmsh+dolfyn (esp. on windows and mac).
>
>
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>
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--
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine