Originally Posted by ghorrocks (Post 751710)

Have a look in the documentation on the numerical approach. The solver forms control volumes around the nodes, which means for tet meshes the control volumes are polygonal. If you use a structured mesh the control volumes are also hexes, and that makes the control volumes have less faces (so less fluxes to keep track of, less memory) and the control volume faces can potentially be closer to perpendicular which helps reduce numerical diffusion. Hope that gives you some clues for some things to research on this topic.