Question

For an incompressible flow, the mass continuity equation changes to ________

(a) energy equation

(b) momentum equation

(c) volume continuity equation

(d) remains same

I have been asked this question by my school teacher while I was bunking the class.

My enquiry is from Continuity Equation in division Aerodynamics – Fundamental Principles and Equations of Aerodynamics

Answer 1

Right choice is (c) volume continuity equation

To explain I would say: ∇.u=0 – In this equation, u is flow velocity and it states that the divergence of flow velocity is zero. Since the flow is incompressible, the density remains constant and thus the volume cannot be changed.