[Gmsh] RE: Adaptive mesh refinement with getDP and gmsh

Christophe Geuzaine Christophe.Geuzaine at ulg.ac.be
Thu Apr 26 13:30:09 CEST 2001


Jehudi Maes wrote:
> 
> Dear Mr. Geuzaine,
> 
> Thank you for your quick reply. The main problem is indeed the calculation
> the generation of the target mesh size. I think I would better post a
> message regarding this issue on the GetDP mailing list.

Ok.

> 
> Regarding the smooth surface: If I make a plot of the calculated B (Norm B)
> I would like to see the values as a colored triangle (for my 2D) problem.
> Instead of such a plot I get a plot with small colored squares at the middle
> of each triangle.

I guess you output scalar points instead of scalar triangles. I you
generate the view with GetDP, check the Depth option in the
PostOperation (should be 1, and is probably 0).

> 
> My postprocessing file is:
> 
> /*********************************************************************
>  *
>  *  srm.post
>  *
>  *  Post-Processing for the switched reluctance motor
>  *
>  *********************************************************************/
> 
> General.Trackball = 0 ;
> General.RotationX = 0 ;
> General.RotationY = 0 ;
> General.RotationZ = 0 ;
> General.Color.Background = Black ;
> General.Color.Text = White ;
> General.Orthographic = 1 ;
> // Avoid perpective to allow simultaneous plot of B and field lines,
> // make View.OffSetZ>0 to view field lines on top of B plot
> General.Axes = 0 ;
> 
> Geometry.Color.Points = {128,128,128} ; // Remove geometry points in
> postprocessing
> 
> Include "bn.pos" ; // Norm[{d a}] with :
> Include "a.pos" ;  // a Magnetic vector potential a formulation (2D)
> 
> View[0].Name = "B values" ;
> View[0].IntervalsType = 2 ;
> View[0].OffsetZ = 0.0 ;
> View[0].RaiseZ = 0 ;
> View[0].Light = 1 ;
> View[0].ShowScale = 1 ;
> 
> View[1].Name = "Field lines" ;
> View[1].IntervalsType = 1;
> View[1].OffsetZ = 0.1 ;
> View[1].RaiseZ = 0.0 ;
> View[1].Light = 1 ;
> View[1].ColorTable = { White, White } ;
> View[1].NbIso = 20 ;
> View[1].ShowScale = 0 ;
> 
> Kind regards,
> 
> Jehudi Maes
> 
> > -----Original Message-----
> > From: geuzaine at aix10.segi.ulg.ac.be
> > [mailto:geuzaine at aix10.segi.ulg.ac.be]On Behalf Of Christophe Geuzaine
> > Sent: Wednesday, April 25, 2001 7:21 PM
> > To: gmsh at geuz.org
> > Cc: Jehudi.Maes at rug.ac.be; Dular Patrick
> > Subject: Re: [Gmsh] [Fwd: Adaptive mesh refinement with getDP and gmsh]
> >
> >
> > Jehudi Maes wrote:
> > >
> > > Dear Mr. Dular and Mr. Geuzaine,
> > >
> > >  I have been working with GetDP and gmsh for the FE calculations of a
> > > switched reluctance motor (magnetostatic calculations). For these
> > > calculations I have had a lot of help from one of your collegues Johan
> > > Gyselinck. From the websites and the documentation I concluded
> > that it is
> > > possible to use GetDP and gmsh for adaptive mesh generation.
> > Could you be as
> > > kind as to point out how I have to use the combination of GetDP
> > and gmsh for
> > > adaptive mesh generation.
> >
> > For h-type adaptation (i.e. modification of element sizes), you should
> > output a post-processing view which contains the target characteristic
> > lengths. Thus, you should
> >
> > 1) generate a first (coarse) mesh
> > 2) compute target mesh sizes on this mesh, and output the results as a
> >    Gmsh post-processing view
> > 3) load this view in Gmsh, and apply it as the current background mesh
> >    (with 'View->Apply as Background Mesh'), or load the view on the
> >    command line, with the option '-bgm file'
> > 4) re-mesh
> >
> > Step 2) is of course the difficult part, and depends on your problem.
> > GetDP can help to generate the target size view if you have a mean to
> > compute an error field, i.e. some 'volumic' field on the mesh
> > representing (an approximation of) the error. If you can compute such a
> > field, then you can use 'Adapt H1' in a GetDP PostOperation on this
> > field, and you will obtain a valid background mesh for Gmsh.
> >
> > WARNING: if you plan to use background meshes, you need the very latest
> > version (1.18) of Gmsh. This version fixes a serious bug in the
> > generation
> > of adapted 1D meshes.
> >
> > For p-type adaptation (i.e. local modification of interpolation order),
> > you should output an adaptation file, and give it to GetDP on the
> > command line with the '-adapt file' option. The adaptation file can be
> > generated by GetDP by using 'Adapt P1' and by specifying 'Adaptation' in
> > the Format of a PostOperation.
> >
> > >
> > > Regarding the gmsh software I have some problems with the post
> > processing
> > > (generating smooth surface maps), are there any examples
> > (besides t8.geo in
> > > the tutorial) on how to use gmsh for post processing ?
> >
> > What do you mean by a 'smooth surface map' ?
> >
> > The simplest example of post-processing with gmsh is 'gmsh t1
> > view1.pos'. All post-processing options in Gmsh are available by
> > right-clicking on the view button.
> >
> > >
> > > Kind regards,
> > >
> > > Jehudi
> >
> > I have forwarded your mail to the gmsh mailing list. If you reply to
> > this message, please reply to the mailing list.
> >
> >
> > Christophe
> >
> > --
> > Christophe Geuzaine
> >
> > Tel: 32 (0) 4 366 37 10    http://geuz.org
> > Fax: 32 (0) 4 366 29 10    mailto:Christophe.Geuzaine at ulg.ac.be
> >
> 
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-- 
Christophe Geuzaine

Tel: 32 (0) 4 366 37 10    http://geuz.org
Fax: 32 (0) 4 366 29 10    mailto:Christophe.Geuzaine at ulg.ac.be



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