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GATE 2020 AE – Question 17

Aerodynamics · Basic fluid mechanics: kinematics, conservation laws, dimensional analysis, incompressibility and Newtonian fluids · 1 mark · Multiple choice

The figure plots streamlines of a steady two-dimensional flow in a 0.2 m high channel, with stream function Ψ in m²/s. Find volume flow rate per unit depth.

Diagram for GATE 2020 AE question 17
  1. 1.0 m²/s
  2. 2.0 m²/s
  3. 0.5 m²/s
  4. 0.1 m²/s

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Correct answer: (B) 2.0 m²/s

Explanation

In two-dimensional incompressible flow, discharge per unit depth between streamlines equals their stream-function difference. The walls have Ψ = −1 and Ψ = +1 m²/s. Thus $q=1-(-1)=2$ m²/s, B. The channel height need not be multiplied again because Ψ already encodes the integrated velocity.

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