cavity.geo

// Unit cube, purely hexahedral
lc = 1.0; // not really used since we set explicit divisions below

// 8 corner points of a 1x1x1 cube
Point(1) = {0, 0, 0, lc};
Point(2) = {1, 0, 0, lc};
Point(3) = {1, 1, 0, lc};
Point(4) = {0, 1, 0, lc};
Point(5) = {0, 0, 1, lc};
Point(6) = {1, 0, 1, lc};
Point(7) = {1, 1, 1, lc};
Point(8) = {0, 1, 1, lc};

// 12 edges
Line(1) = {1, 2}; Line(2) = {2, 3}; Line(3) = {3, 4}; Line(4) = {4, 1};
Line(5) = {5, 6}; Line(6) = {6, 7}; Line(7) = {7, 8}; Line(8) = {8, 5};
Line(9)  = {1, 5}; Line(10) = {2, 6}; Line(11) = {3, 7}; Line(12) = {4, 8};

// 6 faces
Line Loop(1) = {1, 2, 3, 4};      Plane Surface(1) = {1};  // bottom
Line Loop(2) = {5, 6, 7, 8};      Plane Surface(2) = {2};  // top
Line Loop(3) = {1, 10, -5, -9};   Plane Surface(3) = {3};  // front
Line Loop(4) = {2, 11, -6, -10};  Plane Surface(4) = {4};  // right
Line Loop(5) = {3, 12, -7, -11};  Plane Surface(5) = {5};  // back
Line Loop(6) = {4, 9, -8, -12};   Plane Surface(6) = {6};  // left

Surface Loop(1) = {1, 2, 3, 4, 5, 6};
Volume(1) = {1};

// --- Number of cells per edge direction ---
N = 20; // 20x20x20 = 8,000 hex cells

Transfinite Line {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12} = N + 1;

Transfinite Surface {1, 2, 3, 4, 5, 6};
Recombine Surface {1, 2, 3, 4, 5, 6};

Transfinite Volume {1};

// Physical Surface & Volume Groups
Physical Surface("lid") = {2};
Physical Surface("walls") = {1, 3, 4, 5, 6};
Physical Volume("fluid") = {1};

Mesh 3;