Section 4: Soil and Water Conservation Engineering
Fluid Mechanics
Subtopic: Flow in open channels
Question Statement:
A discharge of 10 m³ s⁻¹ passes through a 4 m wide rectangular channel at a depth of 1.25 m. The slope of the channel is 9.08 × 10⁻³. The depth for minimum specific energy is
Options:
(A) 0.56 m
(B) 0.66 m
(C) 0.86 m
(D) 1.06 m
Official Answer Key:
C
Step-by-Step Solution & Explanation
Depth of minimum specific energy = critical depth, y_c = (q²/g)^(1/3), where q = Q/b = 10/4 = 2.5 m²/s (unit discharge). y_c = (2.5²/9.81)^(1/3) = (0.6371)^(1/3) = ≈0.86 m.
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