Section 4: Soil and Water Conservation Engineering
Fluid Mechanics
Subtopic: Laminar and turbulent flow in pipes, Darcy–Weisbach and Hazen–Williams equations
Question Statement:
The viscosity of milk at 21 °C is 2.1×10⁻³ Pa·s and its density at this temperature is 1029 kg m⁻³. Milk flows at the rate of 0.12 m³ min⁻¹ in a 2.5 cm diameter pipe. At 21 °C, the flow of milk will be
Options:
(A) stream line
(B) laminar
(C) transition
(D) turbulent
Official Answer Key:
D
Step-by-Step Solution & Explanation
Q = 0.12/60 = 0.002 m³/s; A = π/4×0.025² = 4.909×10⁻⁴ m²; V = Q/A = 4.074 m/s. Re = ρVD/μ = 1029×4.074×0.025/(2.1×10⁻³) ≈ 49,900, well above 4000 → turbulent flow.
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