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GATE 2026 AE – Question 43

Aerodynamics · Basic fluid mechanics: kinematics, conservation laws, dimensional analysis, incompressibility and Newtonian fluids · 2 marks · Multiple choice

An experimental study is planned to map out the low-Reynolds number incompressible steady two-dimensional aerodynamic characteristics of a promising novel airfoil. The operational parameters of the problem are the speed, density and viscosity of the freestream, the chord of the airfoil and its angle of attack. If the objective is to achieve this with the minimum number of test runs $N_{min}$ while taking 10 equally-spaced test values of each independent parameter of the problem in a suitable range, then $N_{min}$ is ________.

  1. 10
  2. 100
  3. 10,000
  4. 1,00,000

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Correct answer: (B) 100

Explanation

By dimensional analysis the problem has 5 dimensional parameters (speed, density, viscosity, chord, angle) and 3 fundamental dimensions (mass, length, time), which leaves $5 - 3 = 2$ independent dimensionless parameters: the Reynolds number and the angle of attack. Ten values of each need $10^2 = 100$ runs.