Question

The area of the duct is either maximum or minimum when the_________

(a) Mach number = 1

(b) Mach > 1

(c) Mach = 0

(d) Mach < 0

The question was posed to me during an internship interview.

My question is taken from Flow of Compressible Fluid through Orifices and Nozzles topic in chapter Compressible Flow of Fluid Mechanics

Answer 1

Right choice is (a) Mach number = 1

For explanation I would say: Mass flow rate is given by Q = m/p. This is a relation expressed for mass flow rate. The area of the duct is either maximum or minimum when the Mach number of the fluid flow is exactly one.