GATE 2020 AE – Question 18

Aerodynamics · Special topics: Fanno flow, Rayleigh flow, U-tube manometers and Pitot probe · 1 mark · Multiple choice

Which can increase the Mach number of supersonic duct flow?

Increase duct length.
Add heat.
Remove heat.
Insert a convergent–divergent section whose inlet and exit areas are equal.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (C) Remove heat.

Explanation

For supersonic Rayleigh flow, heat addition drives Mach number toward one, while heat removal drives it away from one and can increase it. Friction in a longer Fanno duct also drives supersonic flow toward one. An ideal equal-area inlet and exit does not itself provide a net isentropic Mach increase. Thus heat removal, C.

More Special topics: Fanno flow, Rayleigh flow, U-tube manometers and Pitot probe questions

GATE 2024 AE Q59 – Consider the following Fanno flow problem: Flow enters a constant area duct at a…
GATE 2025 AE Q46 – An aircraft is flying at an altitude of 4500 m above sea level, where the ambient…
GATE 2025 AE Q50 – A perfect gas flows through a frictionless constant-area duct with heat addition. The…
GATE 2026 AE Q30 – A flow is steady, inviscid and one-dimensional, with no shaft work or body forces. Which…
GATE 2026 AE Q65 – A Mach 1.5 air flow enters a round duct of length 20 cm and diameter 3 cm. If the flow…
GATE 2022 AE Q14 – The point of maximum entropy on a Fanno-curve in a Temperature-Entropy (T-s) diagram…

All Special topics: Fanno flow, Rayleigh flow, U-tube manometers and Pitot probe questions →