Conservation and Constitutive Equations in Curvilinear Coordinates

The formulation of the conservation and constitutive differential equations derived in the previous chapters was obtained under the implicit assumption that the coordinate system was a Cartesian one. In practical problems it is sometime useful to switch to more natural coordinate systems, where the actual form of the differential equations may be simplified, thanks to some symmetry properties of the problem. For example, when dealing with the heating and evaporation of a spherical drop, the natural coordinate system is the spherical one, since in such a system the governing differential equations may assume a much simpler form.