The 'Manning''s equation' for uniform flow in an open channel gives velocity as:
Choose the correct answer
V = n × R^(2/3) × S^(1/2)
V = (1/n) × R^(2/3) × S^(1/2) — velocity proportional to hydraulic radius to 2/3 power and square root of slope
V = (1/n) × R × S (wrong exponents)
V = C × R^(1/2) × S^(1/2) (Chezy, not Manning)
Correct Answer
B. V = (1/n) × R^(2/3) × S^(1/2) — velocity proportional to hydraulic radius to 2/3 power and square root of slope
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Manning''s equation: V = (1/n) × R^(2/3) × S^(1/2) (SI units). R = hydraulic radius = A/P (m). S = bed slope (m/m). n = roughness. Discharge Q = A × V = A × (1/n) × R^(2/3) × S^(1/2). Normal depth y_n: set A(y_n)×R(y_n)^(2/3) = Q×n/S^(1/2). Also: V = C√(RS) where C = R^(1/6)/n (Chezy-Manning relation between Manning and Chezy coefficients).
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