Question

Which of these results in decrease of the flow inside the actual supersonic diffuser?

(a) Test section

(b) Convergent nature

(c) Divergent nature

(d) Shock waves

I got this question in an interview for internship.

Question is taken from Compressible Flow through Diffusers topic in section Compressible Flow through Nozzles, Diffusers and Wind Tunnels of Aerodynamics

Answer 1

Correct answer is (d) Shock waves

For explanation I would say: In case of actual supersonic diffuser, there’s a series of oblique shock formations. It’s present in the convergent and the test section of the wind tunnel. The interaction between the viscous flow and the shock waves resulting in slowing down the flow velocity.