recombined quad mesh does not respect "Line in Surface" geometry
I have this simple .geo file that create a pure quad mesh. However the nodes of the quads along the crack does not respect the 1D mesh.
Click to expand .geo file
''' p1 = newp; Point(p1) = { 0, 0, 0 };p2 = newp; Point(p2) = { 1, 0, 0 };
p3 = newp; Point(p3) = { 0, 1, 0 };
p4 = newp; Point(p4) = { 1, 1, 0 };
p5 = newp; Point(p5) = { 0.5, 0, 0 };
p6 = newp; Point(p6) = { 0.5, 0.5, 0 };
Line(1) = { p1, p5 };
Line(2) = { p5, p2 };
Line(3) = { p2, p4 };
Line(4) = { p4, p3 };
Line(5) = { p3, p1 };
Line(6) = { p5, p6 };
Line Loop(7) = { 1, 2, 3, 4, 5 };
Plane Surface(8) = { 7 };
Line{ 6 } In Surface {8};
Line Loop(19) = { 5, -6, 10, -11, 12, -13 };
Physical Line( "Crack" ) = { 6 };
Physical Line( "MaxU" ) = { 4 };
Physical Line( "MaxV" ) = { 3 };
Physical Line( "MinU" ) = { 1, 2 };
Physical Line( "MinV" ) = { 5 };
Physical Surface( "Material_0" ) = { 8 };
Mesh.CharacteristicLengthFactor = 1;
Mesh.ElementOrder = 1;
Mesh.RecombinationAlgorithm = 2;
Mesh.RecombineAll = 1;
'''
Here are the geometry and mesh side by side:
By shrinking elements, we can clearly see that the 1D mesh has a different discretization than the 2D mesh. Without triangle recombination, the 1D and 2D match: