Question

Gauss divergence is applied to which of these terms?

(a) Instantaneous total change of B inside the control mass

(b) Instantaneous total change of B within the control volume

(c) Net flow of B into and out of the control volume

(d) Net flow of B into and out of the control mass

I had been asked this question in an interview.

The query is from Governing Equations in chapter Governing Equations of Fluid Dynamics of Computational Fluid Dynamics

Answer 1

Right choice is (c) Net flow of B into and out of the control volume

The explanation: The term representing ‘net flow of B into and out of the control volume’ is a surface integral. This surface integral is converted into a volume integral using the Gauss divergence theorem.