[Gmsh] lower limit for characteristic length

Zenker, Dr. Matthias Matthias.Zenker at erbe-med.de
Wed Jan 7 11:34:23 CET 2009


Thank you, this is very practical for defining fields.

However, I cannot see the fields graphically. When I use the "Put on
view" button and click on "New view", a colorbar appears, but nothing
changes at the location where the field is. 

Did I miss something?

Matthias

> -----Original Message-----
> From: Christophe Geuzaine [mailto:cgeuzaine at ulg.ac.be] 
> Sent: Wednesday, January 07, 2009 7:50 AM
> To: Zenker, Dr. Matthias
> Cc: gmsh at geuz.org
> Subject: Re: [Gmsh] lower limit for characteristic length
> 
> Zenker, Dr. Matthias wrote:
> > Hi,
> > 
> > (just returned from holidays...)
> > thank you for the hint with the fields, I will try it that way.
> > I have examined demos/fields.geo. Seems like I have to 
> enter all that 
> > field-related stuff by hand. I don't mind to do so, but is there a 
> > more elegant way, using the GUI? And can I visualize the defined 
> > fields before starting the meshing?
> 
> Yes: download the latest nightly snapshot, and in the Mesh 
> module click on "Define", then "Fields".
> 
> 
> 
> > 
> > Best regards,
> > 
> > Matthias
> > 
> >> -----Original Message-----
> >> From: Christophe Geuzaine [mailto:cgeuzaine at ulg.ac.be] 
> >> Sent: Tuesday, December 16, 2008 9:41 AM
> >> To: Zenker, Dr. Matthias
> >> Cc: gmsh at geuz.org
> >> Subject: Re: [Gmsh] lower limit for characteristic length
> >>
> >> Zenker, Dr. Matthias wrote:
> >>> Of course. Here it is. 
> >>>
> >>> BTW, I use gmsh 2.2.6 on a WIN XP SP 2, Pentium 4, 3.2 GHz, 
> >> 1.5 GB RAM 
> >>> computer.
> >>>
> >> The default random perturbation factor seems to be a bit 
> >> small in your case. The following (increased "-rand" from 
> >> "1.e-9" to "1.e-7")
> >>
> >>    gmsh small_cl.geo -2 -rand 1.e-7
> >>
> >> seems to work just fine, but I had to stop it before the end 
> >> due to insufficient memory on my laptop. Multiplying all the 
> >> element sizes by 3 and using the faster del2d algorithm
> >>
> >>    gmsh small_cl.geo -2 -rand 1.e-7 -clscale 3 -algo del2d
> >>
> >> produced a nice mesh with about 23 million triangles.
> >>
> >>
> >>> If I could force gmsh not to ignore the cl of the spline control 
> >>> points, it would probably be faster for such a case (if 
> it wouldn't 
> >>> crash). Is there a trick to do that? Would it help to put 
> isolated 
> >>> points with the desired cl at the desired location?
> >> You should probably use Fields to fine-tune the element 
> >> sizes. There are some examples on the mailing list, as well 
> >> as in demos/fields.geo.
> >>
> >>
> >>
> >>> Thank you and best regards,
> >>>
> >>> Matthias
> >>>
> >>>> -----Original Message-----
> >>>> From: Christophe Geuzaine [mailto:cgeuzaine at ulg.ac.be] 
> >>>> Sent: Monday, December 15, 2008 1:07 PM
> >>>> To: Zenker, Dr. Matthias
> >>>> Cc: gmsh at geuz.org
> >>>> Subject: Re: [Gmsh] lower limit for characteristic length
> >>>>
> >>>> Zenker, Dr. Matthias wrote:
> >>>>> Hi there,
> >>>>>  
> >>>>> the question remains: is there a lower limit for the 
> >> characteristic 
> >>>>> length cl, and why does gmsh crash when some points have 
> >> a small cl?
> >>>> It shouldn't crash, except when "cl" divided by the overall 
> >>>> size of model is getting close to machine accuracy (or more 
> >>>> accurately, close to the value of the random pertutbation 
> >>>> used in the meshing algorithms, which is 1e-9 by default).
> >>>>
> >>>> Could you send a file that shows the problem?
> >>>>
> >>>>
> >>>>> I would like to add another one: Is it possible that gmsh 
> >>>> ignores the 
> >>>>> cl of the control points of a spline except for the first 
> >> and last 
> >>>>> one? If
> >>>> That's what Gmsh does: the cls of the control points are ignored.
> >>>>
> >>>>
> >>>>
> >>>>> so, is there a way to force gmsh to take into account the 
> >> cl of the 
> >>>>> intermediate points also?
> >>>>>  
> >>>>> Best regards,
> >>>>>  
> >>>>> Matthias
> >>>>>
> >>>>>     
> >>>> --------------------------------------------------------------
> >>>> ----------
> >>>>>     *From:* gmsh-bounces at geuz.org 
> >> [mailto:gmsh-bounces at geuz.org] *On
> >>>>>     Behalf Of *Zenker, Dr. Matthias
> >>>>>     *Sent:* Monday, November 17, 2008 10:49 AM
> >>>>>     *To:* gmsh at geuz.org
> >>>>>     *Subject:* Re: [Gmsh] lower limit for characteristic length
> >>>>>
> >>>>>     I was wrong, it crashes also for cl=0.0005 (but after a 
> >>>> looong time,
> >>>>>     and with a runtime error).
> >>>>>
> >>>>>         
> >>>> --------------------------------------------------------------
> >>>> ----------
> >>>>>         *From:* gmsh-bounces at geuz.org 
> >>>> [mailto:gmsh-bounces at geuz.org] *On
> >>>>>         Behalf Of *Zenker, Dr. Matthias
> >>>>>         *Sent:* Monday, November 17, 2008 10:16 AM
> >>>>>         *To:* gmsh at geuz.org
> >>>>>         *Subject:* [Gmsh] lower limit for characteristic length
> >>>>>
> >>>>>         Hi,
> >>>>>
> >>>>>         I wonder if there is a lower limit for the 
> characteristic
> >>>>>         length. I have a rather simple 2D geometry, and if 
> >>>> I set the cl
> >>>>>         for just two points to 0.0001, gmsh crashes during 
> >>>> the meshing
> >>>>>         after having given the error message "3 identical 
> >> points in
> >>>>>         Qtest". The .gmsh-errors file is not written. With 
> >>>> cl=0.0005,
> >>>>>         this does not happen (but it takes veeery long to 
> >>>> compute the mesh).
> >>>>>         Best regards,
> >>>>>
> >>>>>         Matthias
> >>>>>
> >>>>>         
> >>>> ----------------------------------------------------------------
> >>>>>         ERBE Elektromedizin GmbH
> >>>>>         Dr.rer.nat. Matthias Zenker
> >>>>>         Dipl. Phys.
> >>>>>         Grundlagenentwicklung Technologie
> >>>>>         Waldhoernlestrasse 17
> >>>>>         D-72072 Tuebingen
> >>>>>         Tel.: + 49 (0) 7071 - 755 226
> >>>>>         Fax: + 49 (0) 7071 - 755 5226
> >>>>>         E-Mail: <_mailto:Matthias.Zenker at ERBE-med.de_>
> >>>>>         URL: _http://www.ERBE-med.de_
> >>>>>         
> >>>>> ----------------------------------------------------------------
> >>>>>
> >>>>>
> >>>>>
> >>>>>           	  	 
> >>>>>
> >>>>>         ERBE Elektromedizin GmbH
> >>>>>         Firmensitz: 72072 Tuebingen
> >>>>>         Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> >>>>>         Registergericht: Stuttgart HRB 380137
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>       	  	 
> >>>>>
> >>>>>     ERBE Elektromedizin GmbH
> >>>>>     Firmensitz: 72072 Tuebingen
> >>>>>     Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> >>>>>     Registergericht: Stuttgart HRB 380137
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>   	  	 
> >>>>>
> >>>>> ERBE Elektromedizin GmbH
> >>>>> Firmensitz: 72072 Tuebingen
> >>>>> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> >>>>> Registergericht: Stuttgart HRB 380137
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >> 
> ----------------------------------------------------------------------
> >>>>> --
> >>>>>
> >>>>> _______________________________________________
> >>>>> gmsh mailing list
> >>>>> gmsh 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
> >>>>
> >>>
> >> 
> _____________________________________________________________________
> >>> ERBE Elektromedizin GmbH
> >>> Firmensitz: 72072 Tuebingen
> >>> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> >>> Registergericht: Stuttgart HRB 380137
> >>>
> >>>
> >>>
> >>>
> >> --------------------------------------------------------------
> >> ----------
> >>> _______________________________________________
> >>> gmsh mailing list
> >>> gmsh 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
> >>
> >>
> >>
> > 
> > 
> _____________________________________________________________________
> > ERBE Elektromedizin GmbH
> > Firmensitz: 72072 Tuebingen
> > Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> > Registergericht: Stuttgart HRB 380137
> > 
> > 
> > _______________________________________________
> > gmsh mailing list
> > gmsh 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
> 
> 

_____________________________________________________________________
ERBE Elektromedizin GmbH
Firmensitz: 72072 Tuebingen
Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
Registergericht: Stuttgart HRB 380137