[Gmsh] Small characteristic length -> Bad mesh ?

[Taras Danilchenko]

Hello,
 
 I'm using GMSH which I find  a very
powerful mesh generator. Actually with 2D meshing , I have not special
problems, but when I tried to make mesh for 2d surface with BSpline
boundary, I noticed that sometimes it does not work  correctly,
especially when I reduce characteristic length.

AxiSym_Cyl_Jet.geo file give a good mesh only with h1 >= 0.002

Is it a bag, or the small characteristic length always leads to bad mesh ?

 Thanks in advance.

Taras Danilchenko
SRI SET
St-Petersburg
Russia

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/* Gmsh AxiSym_Cyl_Jet.geo file. Written by Danilchenko T.Y. taras at ton.net.ru*/

p1=newp; Point(p1) = {  0                       ,0                      ,0, h};
p2=newp; Point(p2) = {  R_of_pa                 ,0                      ,0, h};
p3=newp; Point(p3) = {  R_of_pa                 ,H_of_pa                ,0, h};
p4=newp; Point(p4) = {          0               ,       H_of_pa         ,0, h};
p5=newp; Point(p5) = {  R_c                     ,0                      ,0, h1};
p6=newp; Point(p6) = {  R_c                     ,h_c                            ,0,h1 };
p7=newp; Point(p7) = {  R_I*Cos(Angle_I)        ,h_c+R_c+R_I*Sin(Angle_I)       ,0,h1};
p8=newp; Point(p8) = {  0                       ,h_c+R_c+R_I                    ,0, h1};
p9=newp; Point(p9) = {  0               ,h_c                    ,0, h};
p10=newp; Point(p10) = {        0               ,h_c+R_c                ,0,  h1};
p11=newp; Point(p11) = {        0               ,h_c+R_c+R_I/3          ,0,  h1};
p12=newp; Point(p12) = {        0               ,h_c+R_c+R_I/3+R_I/4            ,0,  h1};
p13=newp; Point(p13) = {        0               ,h_c+R_c+R_I/3-R_I/4            ,0,  h1};
p14=newp; Point(p14) = {        R_I/16          ,h_c+R_c+R_I/3          ,0,  h1};
p15=newp; Point(p15) = {1.08*R_I*Cos(Pi/4+Angle_I/2)    ,h_c+R_c+1.08*R_I*Sin(Pi/4+Angle_I/2)   ,0,h1};

Line(1) = {1,5};
Line(2) = {5,2};
Line(3) = {2,3};
Line(4) = {3,4};
Line(5) = {4,8};
Line(6) = {8,12};
Ellipse(61) = {12,11,12,14};
Ellipse(62) = {14,11,12,13};
Line(63) = {13,10};
Line(64) = {13,12};
Line(7) = {10,9};
Line(8) = {9,1};
Line(10) = {6,5};
Circle(11) = {6,9,10};

BSpline(19) = {8,8,8,15,7,7,10,10,10}; 

Line Loop(65) = {2,3,4,5,19,-11,10};
Plane Surface(9000010) = {65};
Line Loop(9000011) = {-19,6,61,62,63};
Plane Surface(9000012) = {9000011};
Line Loop(9000013) = {62,64,61};
Plane Surface(9000014) = {9000013};

Tank_Surf[] = {2,3,4,11,10}; 
Diel1 = 9000001;Physical Surface(Diel1)={9000010};
Diel2 = 9000002;Physical Surface(Diel2)={9000012};
Diel3 = 9000003;Physical Surface(Diel3)={9000014};
Ground = 9000009;Physical Line(Ground)={Tank_Surf[]};
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