[Gmsh] Some questions on tutorial 5

[Christophe Geuzaine]

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