Question

The incorrect equation for the normal shock equation is_______

(a) ρ1u1=ρ2u2

(b) p1+ρ1u\(_1^2\)=p2+ρ2u\(_2^2\)

(c) h1+\(\frac {u_1^2}{2}\)=h2+\(\frac {u_2^2}{2}\)

(d) ∇.v=0

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

My query is from The Basic Normal Shock Equations topic in portion Normal Shock Waves of Aerodynamics

Answer 1

Correct choice is (d) ∇.v=0

Explanation: The normal shock wave analysis has the basic equations which are the continuity equation ρ1u1=ρ2u2, momentum equation p1+ρ1u\(_1^2\)=p2+ρ2u\(_2^2\) and the energy equation h1+\(\frac {u_1^2}{2}\)=h2+\(\frac {u_2^2}{2}\). The equation ∇.v=0 is the incompressible flow equation for a steady flow. The normal shock wave is a compressible flow.