[Gmsh] How to have a non constant carachteristic length between to spherical surfaces

[moritz braun]

Dear All

The geo file below



====================================================
lcar = 0.05;

Function Mysphere;

  // In the following commands we use the reserved variable name
  // `newp', which automatically selects a new point number. This
  // number is chosen as the highest current point number, plus
  // one. (Note that, analogously to `newp', the variables `newc',
  // `news', `newv' and `newreg' select the highest number amongst
  // currently defined curves, surfaces, volumes and `any entities
  // other than points', respectively.)

  p1 = newp; Point(p1) = {x,  y,  z,  lcar} ;
  p2 = newp; Point(p2) = {x+r,y,  z,  lcar} ;
  p3 = newp; Point(p3) = {x,  y+r,z,  lcar} ;
  p4 = newp; Point(p4) = {x,  y,  z+r,lcar} ;
  p5 = newp; Point(p5) = {x-r,y,  z,  lcar} ;
  p6 = newp; Point(p6) = {x,  y-r,z,  lcar} ;
  p7 = newp; Point(p7) = {x,  y,  z-r,lcar} ;

  c1 = newreg; Circle(c1) = {p2,p1,p7};
  c2 = newreg; Circle(c2) = {p7,p1,p5};
  c3 = newreg; Circle(c3) = {p5,p1,p4};
  c4 = newreg; Circle(c4) = {p4,p1,p2};
  c5 = newreg; Circle(c5) = {p2,p1,p3};
  c6 = newreg; Circle(c6) = {p3,p1,p5};
  c7 = newreg; Circle(c7) = {p5,p1,p6};
  c8 = newreg; Circle(c8) = {p6,p1,p2};
  c9 = newreg; Circle(c9) = {p7,p1,p3};
  c10 = newreg; Circle(c10) = {p3,p1,p4};
  c11 = newreg; Circle(c11) = {p4,p1,p6};
  c12 = newreg; Circle(c12) = {p6,p1,p7};

  // We need non-plane surfaces to define the spherical holes. Here we
  // use ruled surfaces, which can have 3 or 4 sides:

  l1 = newreg; Line Loop(l1) = {c5,c10,c4};   Ruled Surface(newreg) = {l1};
  l2 = newreg; Line Loop(l2) = {c9,-c5,c1};   Ruled Surface(newreg) = {l2};
  l3 = newreg; Line Loop(l3) = {c12,-c8,-c1}; Ruled Surface(newreg) = {l3};
  l4 = newreg; Line Loop(l4) = {c8,-c4,c11};  Ruled Surface(newreg) = {l4};
  l5 = newreg; Line Loop(l5) = {-c10,c6,c3};  Ruled Surface(newreg) = {l5};
  l6 = newreg; Line Loop(l6) = {-c11,-c3,c7}; Ruled Surface(newreg) = {l6};
  l7 = newreg; Line Loop(l7) = {-c2,-c7,-c12};Ruled Surface(newreg) = {l7};
  l8 = newreg; Line Loop(l8) = {-c6,-c9,c2};  Ruled Surface(newreg) = {l8};
  theloops[t] = newreg;
  Surface Loop(theloops[t]) = {l8+1,l5+1,l1+1,l2+1,l3+1,l7+1,l6+1,l4+1};

Return

x = 0.0 ; y = 0.0 ; z = 0 ; r = 2.0 ; t=0;
Call Mysphere ;
x = 0 ; y = 0.0 ; z = 0 ; r = 1.0 ; t=1;
Call Mysphere ;

Volume (186)={theloops[]};
Physical Volume(999)= 186;
===============================

creates a mesh with constant lc=0.05
between r=1 and r=2
I would like to have the lc value increase with growing r.
However, if I use different lc values for the two calls to Mysphere
the result is a sphere of radius 2 instead of the mesh for the desired
shell!
Any ideas how to fix this would be appreciated!


regards

Moritz
-- 
Prof M Braun         Tel.:27-12-4298006/8027
Physics Department  Fax.: 27-12-4293643
University of South Africa (UNISA)
moritz.braun at gmail.com
P.O. Box 392
0003
UNISA
 South Africa
http://moritz-braun.blogspot.com
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