Question

In reality what happens due to the interaction of the oblique shock waves with the boundary layer on the walls of the diffuser?

(a) Higher total pressure loss

(b) Reduction of speed

(c) Total pressure increase

(d) Reduced skin friction drag

This question was posed to me in an online quiz.

I need to ask this question from Supersonic Wind Tunnels in chapter Compressible Flow through Nozzles, Diffusers and Wind Tunnels of Aerodynamics

Answer 1

Correct choice is (a) Higher total pressure loss

Explanation: In real scenario far from hypothetical nature of the diffuser, the oblique shock waves interact with the viscous boundary layer of the diffuser wall. This leads to the separation of the boundary layer thereby increasing the total pressure losses. One thing to remember is that the aim of the diffuser is to reduce the flow velocity by low total pressure losses, but the boundary layer separation prevents that from happening.