Question

For a system with a source or sink to be conservative, which of these is correct?

(a) The total source or sink in the domain is divided equally between the elements

(b) The total source or sink in the domain is equal to the net flux through the boundaries

(c) The total source or sink in the domain is not considered for checking conservativeness

(d) Flux leaving the face of one element is equal to the flux entering the neighbouring element

The question was asked in final exam.

I need to ask this question from Discretization Aspects topic in section Basic Aspects of Discretization, Grid Generation with Appropriate Transformation of Computational Fluid Dynamics

Answer 1

Right choice is (b) The total source or sink in the domain is equal to the net flux through the boundaries

To explain: The general condition of equal and opposite fluxes cannot be applied to a system with sources or sinks. For this case, the total source or sink in the domain should be equal to the net flux through the boundaries of the whole domain.