Question

Which of these phenomena attenuates the advantages of greater pressure recovery in an oblique shock diffuser?

(a) Abrupt change of convergent – divergent sections

(b) Shock wave interaction with walls

(c) Isentropic flow

(d) Presence of normal shock

I got this question during an online interview.

I'm obligated to ask this question of Quasi-One-Dimensional Flow Diffusers in section Quasi-One-Dimensional Flow of Aerodynamics

Answer 1

Right answer is (b) Shock wave interaction with walls

The explanation: The viscous boundary layer inside the diffuser wall interacts with the shock wave. This creates an additional loss in total pressure which attenuates.

 In real life, oblique shock diffusers have viscous flow. The presence of shock waves inside the diffuser leads to interaction with the viscous boundary layer of the diffuser walls which leads to additional pressure losses. There’s also friction involved which makes oblique shock diffusers far from the ideal diffusers which have no total pressure losses.