Question

The only irrigation semi-module through which the discharge is not proportional to H1/2 where H is the head causing flow through the module is _____________

(a) kennedy’s gauge outlet

(b) open flume outlet

(c) free pipe outlet

(d) adjustable orifice semi-module

The question was asked during an interview for a job.

My question is based upon Regulation Modules in chapter Regulation Modules and Canal Structure of Irrigation Engineering

Answer 1

The correct option is (b) open flume outlet

The explanation: The discharge through free pipe outlet and Kennedy’s flume outlet is given by-

Q = Cd. A. (2gH)^1/2 where H is the head on U/s side measured from FSL of distributary up to the centre of pipe outlet, Cd is the coefficient of discharge, and A is the area of cross-section of the pipe.

The discharge through an open flume outlet is given as: Q = Cd. W H^3/2 where W is the width of the throat.

The discharge through AOSM is given by- Q = Cd. (W. y0).(2gH)^1/2 where ‘y0’ is the height of an orifice opening.