Difficulty: Medium
Correct Answer: Q = A * V together with V = 0.55 * m * y^0.64
Explanation:
Introduction / Context:
Kennedy’s regime method sizes unlined canals by ensuring that mean velocity equals the “critical velocity” which does not cause silting or scouring. The trial procedure uses continuity and Kennedy’s empirical velocity-depth relation.
Given Data / Assumptions:
Concept / Approach:
Kennedy proposed V = 0.55 * m * y^0.64 (SI units, with m the critical velocity ratio). The trial begins with an assumed section (hence y and A), computes V from the critical velocity relation, and checks Q = A * V. Section parameters are iterated to satisfy both hydraulics and velocity criterion.
Step-by-Step Solution:
Use continuity: Q = A * V.Use Kennedy: V = 0.55 * m * y^0.64.Iterate section dimensions until computed Q matches the design discharge and velocity equals the critical value.
Verification / Alternative check:
Some designers combine Kennedy with Chezy/Manning to ensure slope adequacy; however, the cornerstone relation in the trial is the critical velocity formula with continuity.
Why Other Options Are Wrong:
Common Pitfalls:
Using wrong exponent in V–y relation; omitting the m-factor; failing to reconcile depth with hydraulic slope constraints.
Final Answer:
Q = A * V together with V = 0.55 * m * y^0.64
Discussion & Comments