allows triangular faces for advection

src/scheme/FluxingAdvectionSolver.cpp

@@ -222,6 +222,28 @@ FluxingAdvectionSolver<3>::_computeAlgebraicFluxingVolume()
         TinyMatrix<3> M2(b1, a2 + b2, a3);
         TinyMatrix<3> M3(a1, b2, a3 + b3);
 
+        algebraic_fluxing_volume[face_id] = (det(M1) + det(M2) + det(M3)) / 12;
+      } else if (face_to_node.size() == 3) {
+        const Rd& x0 = old_xr[face_to_node[0]];
+        const Rd& x1 = old_xr[face_to_node[1]];
+        const Rd& x2 = old_xr[face_to_node[2]];
+
+        const Rd& x3 = new_xr[face_to_node[0]];
+        const Rd& x4 = new_xr[face_to_node[1]];
+        const Rd& x5 = new_xr[face_to_node[2]];
+
+        const Rd& a1 = x5 - x1;
+        const Rd& a2 = x5 - x2;
+        const Rd& a3 = x5 - x3;
+
+        const Rd& b1 = x5 - x0;
+        const Rd& b2 = x4 - x0;
+        const Rd& b3 = x2 - x0;
+
+        TinyMatrix<3> M1(a1 + b1, a2, a3);
+        TinyMatrix<3> M2(b1, a2 + b2, a3);
+        TinyMatrix<3> M3(a1, b2, a3 + b3);
+
         algebraic_fluxing_volume[face_id] = (det(M1) + det(M2) + det(M3)) / 12;
       } else {
         throw NotImplementedError("Not implemented for non quad faces");