Question

What is the relation between back pressure and exit pressure in case of subsonic flow at the nizzle’s exit?

(a) pB = pe

(b) pB > pe

(c) pB < pe

(d) pB = 2pe

I got this question at a job interview.

I'm obligated to ask this question of Governing Equations for Quasi One Dimensional Flow topic in section Compressible Flow through Nozzles, Diffusers and Wind Tunnels of Aerodynamics

Answer 1

Right choice is (a) pB = pe

For explanation I would say: Back pressure, which is the pressure downstream the nozzle’s exit is equal to the exit pressure when the flow at the exit is subsonic. This is because of a discrepancy between maintaining a steady subsonic flow in case of pressure difference.