Martin Vymazal wrote:
Dear gmsh users,
I'm trying to generate a second order (P2) unstructured mesh around a
symmetric airfoil. I managed to create a mesh which is fine so far, but
I would like to control precisely the number of points on the airfoil.
To make things a bit more complicated, I'd also like to have more points
close to the leading and trailing edges of the airfoil. I thought I
could use the transfinite algorithm with 'progression' or 'bump'
options, but the progression gives me a bad mesh for a progression ratio
which is not close to 1.0 (I attached my *.geo files, progression 1.3 at
the end of the naca0012 geo file already gives strange results.
Hi Martin,
I think displaying the nodes of the 1D mesh on the lines with "shift-alt-p" or Tools->Options->Mesh->Visibility->Nodes
could help you understanding what happens, the way "bump" and "progression" works in Gmsh and what you call "strange"
results (I see what you mean).
http://geuz.org/gmsh/doc/texinfo/gmsh-full.html#SEC45
The optional argument `Using Progression expression' instructs the transfinite algorithm to distribute the nodes
following a geometric progression (Progression 2 meaning for example that each line element in the series will be twice
as long as the preceding one). The optional argument `Using Bump expression' instructs the transfinite algorithm to
distribute the nodes with a refinement at both ends of the line.
and if you search for "bump" in the mailing-list archives, you get this:
http://www.geuz.org/pipermail/gmsh/2008/003526.html
btw , point 5000 is exactly the same as point 381. It is perhaps not a problem
but you should avoid it.
Cheers,
Dave
--
David Colignon, Ph.D.
Collaborateur Logistique du F.R.S.-FNRS
CÉCI - Consortium des Équipements de Calcul Intensif
ACE - Applied & Computational Electromagnetics
Institut Montefiore B28
Université de Liège
4000 Liège - BELGIQUE
Tél: +32 (0)4 366 37 32
Fax: +32 (0)4 366 29 10
WWW: http://hpc.montefiore.ulg.ac.be/
Agenda: http://www.google.com/calendar/embed?src=david.colignon%40gmail.com
It seems
that gmsh calculates the lengths of the lines on the wall of the airfoil
incorrectly (not precisely enough?). I hoped I could somehow set the
precision with which the spline representing the wall of the airfoil is
meshed and thus fix the problem, but found nothing relevant in the
documentation.
On the other hand, the 'bump' option seems to have no effect whatever
value I use (I tried values between 0.5 and 3.5, but I must admit I
don't know what this number actually means).
I'd appreciate any help/hints or at least an info whether this can be
done in gmsh or not.
Thank you very much,
Martin Vymazal
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