SemiImplicitSource takes constant values for Su,Sp
Functionality to add/problem to solve
The fvOption SemiImplicitSource allows one to directly specify a source term in any equation. It currently only takes constant values for Su (source), Sp (linearisation of source)
Target audience
This fvOption is quite often used to model a heat source in the temperature eqn.
Proposal
Make Su,Sp into Function1