[Gmsh] different result for meshing in x and y direction

[Düdder, Andreas]

Dear gmsh-users,


I ran into a problem with second order meshing of a Ruled Surface. If this surface is oriented along the x axis, I get a bad distortion. If I orient the same surface along the y axis, this problem does not occure. First order meshing work fine in both cases.

Is there a difference in the meshing algorithm for both axes?


An example with the two surfaces oriented along both axis is attached below.


I would appreciate some hints to get a nice meshing in both directions.

Thanks!


Best regards,

Andreas Düdder






d = 0.025;
lc =  0.0007;
r = 0.001;
l = d/2;



//surface parallel to x
c1center = newp; Point(c1center) = {0, 0, 0, lc};
c1_2 = newp; Point(c1_2) = {0, 0,r, lc};
c1_3 = newp; Point(c1_3) = {0, r,0, lc};
circle1_2 = newl; Circle(circle1_2) = {c1_2,c1center,c1_3};

point_s_2 = newp; Point(point_s_2) = {l, 0, 3*r+0.0004, lc};
point_s_3 = newp; Point(point_s_3) = {l, r, 2*r+0.0004, lc};

c2center = newp; Point(c2center) = {d, 0, 0, lc};
c2_2 = newp; Point(c2_2) = {d, 0, r, lc};
c2_3 = newp; Point(c2_3) = {d, r, 0, lc};
circle2_2 = newl; Circle(circle2_2) = {c2_2,c2center,c2_3};

spline_2 = newl; Spline(spline_2) = {c1_2,point_s_2,c2_2};
spline_3 = newl; Spline(spline_3) = {c1_3,point_s_3,c2_3};

axial_surface_2_loop = newll; Line Loop(axial_surface_2_loop) = {spline_2,circle2_2,-spline_3,-circle1_2};
axial_surface_2 = news; Ruled Surface(axial_surface_2) = {axial_surface_2_loop};


//surface parallel to y;
c1center = newp; Point(c1center) = {0, 0, 2*r, lc};
c1_2 = newp; Point(c1_2) = {0, 0, 3*r, lc};
c1_3 = newp; Point(c1_3) = {r, 0, 2*r, lc};
circle1_2 = newl; Circle(circle1_2) = {c1_2,c1center,c1_3};

point_s_2 = newp; Point(point_s_2) = {0, l, 5*r+0.0004, lc};
point_s_3 = newp; Point(point_s_3) = {r, l, 4*r+0.0004, lc};

c2center = newp; Point(c2center) = {0, d, 2*r, lc};
c2_2 = newp; Point(c2_2) = {0, d, 3*r, lc};
c2_3 = newp; Point(c2_3) = {r, d, 2*r, lc};
circle2_2 = newl; Circle(circle2_2) = {c2_2,c2center,c2_3};


spline_2 = newl; Spline(spline_2) = {c1_2,point_s_2,c2_2};
spline_3 = newl; Spline(spline_3) = {c1_3,point_s_3,c2_3};

axial_surface_2_loop = newll; Line Loop(axial_surface_2_loop) = {spline_2,circle2_2,-spline_3,-circle1_2};
axial_surface_2 = news; Ruled Surface(axial_surface_2) = {axial_surface_2_loop};
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