Add mesh files for rectangular domain

Author: nikoscham

tutorials/rect.geo

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+// 2D Rectangle: 4m (width) x 2m (height)
+// With Physical Lines for boundary labeling
+
+lc = 0.2; // Characteristic length (mesh density)
+
+// Points (x, y, z, mesh size)
+Point(1) = {0, 0, 0, lc};     // Bottom left
+Point(2) = {4, 0, 0, lc};     // Bottom right
+Point(3) = {4, 2, 0, lc};     // Top right
+Point(4) = {0, 2, 0, lc};     // Top left
+
+// Lines
+Line(1) = {1, 2}; // bottom
+Line(2) = {2, 3}; // right
+Line(3) = {3, 4}; // top
+Line(4) = {4, 1}; // left
+
+// Line Loop and Surface
+Line Loop(1) = {1, 2, 3, 4};
+Plane Surface(1) = {1};
+
+// Physical Lines
+Physical Line("bottom") = {1};
+Physical Line("right")  = {2};
+Physical Line("top")    = {3};
+Physical Line("left")   = {4};
+
+// Physical Surface (optional, for FEM domains)
+Physical Surface("domain") = {1};
+
+// Generate 2D mesh
+//Recombine Surface{1}; // Turns triangle mesh into quads
+Mesh 2;
+