Question

The flux of one element must have _________ to the flux of the neighbouring element.

(a) different magnitude and equal sign

(b) different magnitude and opposite sign

(c) equal magnitude and equal sign

(d) equal magnitude and opposite sign

This question was posed to me in an international level competition.

My doubt is from Discretization Aspects in chapter Basic Aspects of Discretization, Grid Generation with Appropriate Transformation of Computational Fluid Dynamics

Answer 1

Right option is (d) equal magnitude and opposite sign

The explanation is: Flux leaving the face of one element should be the flux entering the neighbouring element. So, the fluxes of two near-by elements should have equal magnitude and opposite sign. This ensures the conservativeness of the system.