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GATE 2019 AE – Question 16

Aerodynamics · Compressible flows: isentropic flow, normal and oblique shocks, Prandtl-Meyer flow, nozzles and diffusers · 1 mark · Multiple choice

For quasi-one-dimensional isentropic supersonic flow through a diverging duct,

  1. Mach number and static temperature both increase.
  2. Mach number increases and static temperature decreases.
  3. Mach number decreases and static temperature increases.
  4. Mach number and static temperature both decrease.

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Show answer and explanation

Correct answer: (B) Mach number increases and static temperature decreases.

Explanation

The area–velocity relation is $dA/A=(M^2-1)dV/V$. For M>1, a diverging area accelerates the flow. Stagnation enthalpy is constant, so increasing kinetic energy reduces static temperature. The Mach number increases: B.

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