Computer Modeling of Side‐Flow Weirs

Abstract

A new computational procedure is presented that addresses the complex phenomena found in declining‐flow regimes and does not require that the boundary conditions of the declining‐flow segment be defined. These conditions are determined as a part of the solution of the larger problem of determining the flows in the entire conveyance system. The procedure utilizes the principle of conservation of momentum in the declining‐flow segment, coupled with standard water‐profile procedures in the constant‐flow segments. The algorithm determines whether the flow is supercritical, subcritical, or a combination of both. If a hydraulic jump occurs, its location is found, even if it lies within the declining‐flow segment. The procedure is applied specifically to the side‐flow weir, and theoretical computations are compared to experimental values that have been published by others. Excellent correspondence exists between the theoretical and experimental results. Examples of the results for a variety of conditions are presented, including the circumstance in which a hydraulic jump occurs in the weir reach.