Question

The value of Cp for compressible flow can be given as ___________

(a) Cp = P2-P1

(b) Cp = 0

(c) Cp = (P2-P1) /q

(d) Cp = 0.5*ρ*V1^2

The question was asked at a job interview.

This interesting question is from Pressure Coefficient topic in portion Inviscid & Incompressible Flow of Aerodynamics

Answer 1

The correct choice is (d) Cp = 0.5*ρ*V1^2

For explanation: The pressure is given in terms of coefficient rather than the pressure itself. P2-P1 is the pressure difference at two different points in the flow field. ‘q’ is the dynamic pressure which is given by 0.5*ρ*V1^2 and Cp is the coefficient of pressure.