Calculating Flow in Manifold and Orifice System

Abstract

Spatial distribution of water discharge can be obtained through a manifold consisting of main pipes and perforated laterals. This study formulates the problem of discharge distribution among lateral pipes and from laterals through orifices uniformly spaced along them. A nonlinear difference equation for flow in the pipes is solved numerically to determine the driving head as a function of the number of ports and a geometrical ratio. A dimensionless solution for simple manifolds is developed to obtain a direct method of evaluating discharges through all the orifices. The approach presented in this paper makes it possible to formulate the problem of restricting the maximum outlet‐discharge variation through a dividing‐flow manifold. A graphical solution to this problem is obtained that permits one to indicate the lateral‐to‐manifold diameter ratio for limiting this variation to a prescribed value. The results of this paper offer a means for comparing the uniformity of distribution expected from various combinations of the number of orifices and laterals and their sizes for a given manifold.