Convert unstructured mesh to structured mesh

Question

I need help to know, how can I convert an unstructured 2d mesh for structured mesh? (Software Gmsh version 4.9.3).

This is my script in Gmsh.

Mesh.MshFileVersion = 2.2; 

// Geometry

//Points
Point(1) = {0, 1, 0, 0.3};
Point(2) = {0, 2, 0, 0.3};
Point(3) = {7, 2, 0, 0.3};
Point(4) = {7, 0, 0, 0.3};
Point(5) = {1, 1, 0, 0.3};
Point(6) = {1, 0, 0, 0.3};

// Lines

Line(1) = {5, 1};
Line(2) = {1, 2};
Line(3) = {2, 3};
Line(4) = {3, 4};
Line(5) = {4, 6};
Line(6) = {6, 5};

Curve Loop(1) = {1, 2, 3, 4, 5, 6};
Plane Surface(1) = {1};
Transfinite Surface {1};

Answer 1

in Gmsh only planes that have four corner points could be meshed with structured meshes using Trasnfinite option. In your file, the plane is constituted from six points and Gmsh can't mesh it structured. In such cases, you should partition the problem geometry into distinct rectangles (planes with four corner points) so the Trasnfinite option could be applied to them. In the following code, the geometry is modeled using three rectangles:

lc = 0.3;
//Points
Point(1) = {0, 1, 0, lc};
Point(2) = {0, 2, 0, lc};
Point(3) = {7, 2, 0, lc};
Point(4) = {7, 0, 0, lc};
Point(5) = {1, 1, 0, lc};
Point(6) = {1, 0, 0, lc};
Point(7) = {1, 2, 0, lc};
Point(8) = {7, 1, 0, lc};
//Lines
Line(1) = {1,5};
Line(2) = {5,6};
Line(3) = {6,4};
Line(4) = {4,8};
Line(5) = {8,3};
Line(6) = {3,7};
Line(7) = {7,2};
Line(8) = {2,1};
Line(9) = {5,7};
Line(10) = {5,8};
//Curves
Curve Loop(1) = {3,4,-10,2};
Plane Surface(1) = {1};
Curve Loop(2) = {10,5,6,-9};
Plane Surface(2) = {2};
Curve Loop(3) = {1,9,7,8};
Plane Surface(3) = {3};
//
n1 = 4;
n2 = 4;
n3 = n1*5-1;
Transfinite Curve {1,7} = n1;
Transfinite Curve {2,4,5,8,9} = n2;
Transfinite Curve {3,6,10} = n3;
Transfinite Surface {1,2,3};

here are the resulting structured triangular and rectangular (using Recombine 2D option) meshes: