Discharge coefficient of lateral diversion from trapezoidal channel

Abstract

The discharge coefficient of a lateral opening in a prismatic trapezoidal main channel is determined for subcritical flow conditions from considerations of the conservation of energy and the conservation of momentum. The latter requires an empirical relationship for the local downstream component of the spillage velocity with the local downstream velocity in the main part of the channel. The discharge coefficients obtained by both considerations for a broad range of Froude numbers, combination of both side slopes of 1V: mH with m = 0, 0.5, 1.0, and 2.0, and different lengths of lateral opening are found to be nearly the same. The measured water depth just downstream of the lateral opening is not recommended for use in the numerical determination of the discharge coefficient and the reasons are discussed in detail. The discharge coefficient is found to be related to the upstream Froude number and this relationship is empirically established.