Question

Which of these properties remain constant in the ideal isentropic supersonic diffuser?

(a) Total pressure

(b) Velocity

(c) Mach number

(d) Mass flow

I had been asked this question in an international level competition.

My question is from Quasi-One-Dimensional Flow Diffusers topic in section Quasi-One-Dimensional Flow of Aerodynamics

Answer 1

The correct option is (a) Total pressure

For explanation: Isentropic supersonic diffusers have a constant entropy throughout the diffuser duct. Since the entropy is constant, the total pressure along is the duct is also constant. Although this is an ideal case and in reality there are some pressure losses occurring due to the formation of shock waves.