Add fully coupled heavy test that really demonstrates existing Moltre…

…s capability. Required for release in my mind.

problems/simple_diffusion.i

@@ -1,9 +1,13 @@
 [Mesh]
-  # type = GeneratedMesh
-  # dim = 1
-  # nx = 10
-  # xmax = 10
-  file = progression.msh
+  type = GeneratedMesh
+  dim = 3
+  nx = 2
+  ny = 2
+  nz = 2
+  xmin = -1
+  ymin = -1
+  zmin = -1
+  # file = progression.msh
 []
 
 [Variables]

tests/twod_axi_coupled/2d_lattice_structured.geo

@@ -0,0 +1,78 @@
+Geometry.CopyMeshingMethod = 1;
+R = 72.5;
+H = 2*R + 6.75;
+num_segments = 14;
+pitch = R / num_segments;
+x = .237952211;
+fuel_rad = x * pitch;
+graph_rad = pitch;
+lc = 1;
+lx = .4;
+ly = 10;
+
+Point(1) = {0, 0, 0, lc};
+Point(2) = {fuel_rad, 0, 0, lc};
+Point(3) = {graph_rad, 0, 0, lc};
+Point(4) = {0, H, 0, lc};
+Point(5) = {fuel_rad, H, 0, lc};
+Point(6) = {graph_rad, H, 0, lc};
+// fuel top
+Line(1) = {4, 5};
+// graph top
+Line(2) = {5, 6};
+// graph right edge
+Line(3) = {6, 3};
+// graph bottom
+Line(4) = {3, 2};
+// fuel bottom
+Line(5) = {1, 2};
+// fuel-graph interface
+Line(6) = {2, 5};
+// fuel left edge
+Line(7) = {4, 1};
+
+// Fuel
+Line Loop(8) = {1, -6, -5, -7};
+Plane Surface(9) = {8};
+
+// Moderator
+Line Loop(10) = {2, 3, 4, 6};
+Plane Surface(11) = {10};
+
+// Structured
+Transfinite Line{1, 5} = fuel_rad/lx;
+Transfinite Line{2, 4} = (graph_rad - fuel_rad)/lx;
+Transfinite Line{3, 6, 7} = H/ly;
+Transfinite Surface{9};
+Transfinite Surface{11};
+Recombine Surface{9};
+Recombine Surface{11};
+
+fuel_surfaces[] = {9};
+moder_surfaces[] = {11};
+fuel_tops[] = {1};
+fuel_bottoms[] = {5};
+moder_bottoms[] = {4};
+moder_tops[] = {2};
+For xindex In {1:num_segments-1}
+new_f_surface = Translate {xindex*pitch, 0, 0} {
+  Duplicata { Surface{9}; }
+};
+fuel_surfaces += new_f_surface;
+new_m_surface = Translate {xindex*pitch, 0, 0} {
+  Duplicata { Surface{11}; }
+};
+moder_surfaces += new_m_surface;
+fuel_tops += {13 + (xindex - 1) * 8};
+moder_tops += {17 + (xindex - 1) * 8};
+fuel_bottoms += {15 + (xindex - 1) * 8};
+moder_bottoms += {19 + (xindex - 1) * 8};
+EndFor // xindex
+
+Physical Surface("fuel") = { fuel_surfaces[] };
+Physical Surface("moder") = { moder_surfaces[] };
+Physical Line("fuel_tops") = { fuel_tops[] };
+Physical Line("moder_tops") = { moder_tops[] };
+Physical Line("fuel_bottoms") = { fuel_bottoms[] };
+Physical Line("moder_bottoms") = { moder_bottoms[] };
+Physical Line("outer_wall") = { 18 + 8 * (num_segments - 2) };