The GATE Grind

GATE 2026 AE – Question 21

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

In the figure shown below, the flow at the nozzle exit is ________.

A converging-diverging nozzle with the jet leaving to the right. The jet boundary lines diverge outwards from the nozzle lip, and expansion and compression waves cross inside the plume.
  1. overexpanded
  2. underexpanded
  3. ideally expanded
  4. subsonic

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Show answer and explanation

Correct answer: (B) underexpanded

Explanation

The jet boundary bends outwards after the exit, which means the exit pressure is above the ambient pressure and the flow expands further outside the nozzle. That is an underexpanded jet. An overexpanded jet would contract through oblique shocks from the lip.