Question

For incompressible flow, Cp is expressed only in terms of ____________

(a) pressure

(b) density

(c) temperature

(d) velocity

I have been asked this question in semester exam.

My question is taken from Pressure Coefficient in chapter Inviscid & Incompressible Flow of Aerodynamics

Answer 1

Correct option is (d) velocity

Explanation: In incompressible flow, the pressure and velocity at two different points can be given by-

                         P1+0.5*ρ*V1^2 = P2+0.5*ρ*V2^2

From here we get, P2-P1 = 0.5*ρ (V1^2– V2^2)

Hence, Cp = (P2-P1)/q

Where q-dynamic pressure

On solving the above equation we get, Cp = 1 – (V2/ V1)^2.