GATE_AE_2027_MOCK_02_Q44
GATE 2027 Aerospace Engineering All-India Master Mock 02 (Compressible Aerodynamics & High-Speed Propulsion)
MCQ · 2 Marks
Aerodynamics & Fluid Mechanics • Compressible Flow & Shocks • Rayleigh and Fanno Flow
In 1D Fanno flow (adiabatic flow with wall friction in a constant area duct), what happens to Mach number as flow proceeds downstream?
(A) Mach number always approaches 1.0 regardless of whether inlet is subsonic or supersonic
(B) Subsonic flow accelerates to supersonic speeds without a throat
(C) Supersonic flow accelerates to higher Mach numbers
(D) Stagnation pressure increases along the duct due to viscous friction
Answer Key:
A
Step-by-Step Verified Solution
### Solution: Friction causes entropy to increase. In the Fanno line $T-s$ diagram, maximum entropy occurs at $M = 1.0$. Therefore, subsonic flow accelerates toward $M=1$ and supersonic flow decelerates toward $M=1$. Correct: A.