Question

There is no difference between Navier-Stokes and Euler equations with respect to the continuity equation. Why?

(a) Convection term plays the diffusion term’s role

(b) Diffusion cannot be removed from the continuity equation

(c) Its source term balances the difference

(d) The continuity equation by itself has no diffusion term

I got this question in examination.

Query is from Euler Equation in chapter Governing Equations of Fluid Dynamics of Computational Fluid Dynamics

Answer 1

Correct option is (d) The continuity equation by itself has no diffusion term

The explanation is: Diffusion term, in general, is given by div(ΓgradΦ). For the continuity equation, Φ=1. And grad Φ=0. So, the continuity equation by itself has no diffusion term.