TWO-DIMENSIONAL FREE SURFACE FLOW OVER A SPILLWAY—A NUMERICAL MODEL CASE STUDY

Abstract

ABSTRACT Spillway is a hydraulic structure that is usually provided at storage and diversion dams to release surplus or flood water that cannot be safely stored in the reservoir in order to prevent damage to the dam. Spillway flows are essentially rapidly varied flows near crest with pronounced curvature of the streamlines in vertical direction. Because of the changes of flow boundaries in a short distance, vertical acceleration plays a dominant role in the flow as compared to shear resistance at the solid boundary. The main difficulties while solving the spillway problem numerically are: rapidly varied flow, existence of both subcriticai and supercritical flows, development of turbulent boundary layer, unknown free surface and air entrainment. Numerical simulation of rapidly varied, supercritical, free surface turbulent flow over spillway with all flow characteristics is a challenging task. This paper describes the formulation and development of a numerical model for flow over a spillway. The computer model is developed using the Finite Volume Method based on Euler form of weakly compressible flow equations. The model is applied to a case study to investigate the hydraulic characteristics of flow over spillway crest profile by simulating the velocity distribution, pressure distribution and discharge characteristics. The numerical model results are compared with the physical model results and found to be satisfactory.