This template computes the flux of a vector field through a surface defined over a triangle. The field can be specified in its own coordinate system. The surface is given in Cartesian coordinates, either explicitly by using two coordinates as parameters, or parametrically by giving  as functions of two other parameters. The triangle is specified by giving its vertices, and these are interpreted as points in the plane of the parameters.

VectorCalculus[Flux]

VectorCalculus[SurfaceInt]