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Fluid Mechanics
Bernoulli's Equation & Flow
GATE 2023
Medium

Air (density = 1.2 kg/m³, kinematic viscosity = 1.5×10⁻⁵ m²/s) flows over a flat plate with a free-stream velocity of 2 m/s. The wall shear stress at a location 15 mm from the leading edge is τw. What is the wall shear stress at a location 30 mm from the leading edge?

  • Aτw/2
  • B√2 τw
  • C2 τw
  • τw/√2

Explanation

For a laminar boundary layer over a flat plate, the local wall shear stress scales as τw ∝ x^(-1/2) (from the Blasius solution). Doubling x from 15mm to 30mm therefore scales τw by 1/√2.

Source: GATE ME 2023 Official Paper (2023)

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