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GATE 2020 AE – Question 15

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

Complete body geometry and surface pressure/shear-stress distributions are known for a body in uniform flow. One can estimate

  1. Moment coefficient and force.
  2. Force coefficient and force.
  3. Moment coefficient and moment.
  4. Force and moment.

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Correct answer: (D) Force and moment.

Explanation

Integrating surface traction gives force, $\mathbf F=\int_S\mathbf t\,dS$, and its moment about a selected origin, $\mathbf M=\int_S\mathbf r\times\mathbf t\,dS$. Nondimensional coefficients additionally need reference dynamic pressure and reference dimensions; flow density and speed are not provided. Thus dimensional force and moment are determined, D.

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