SIMULATION OF FLOW CHARACTERISTICS OVER A BROAD CRESTED WEIR USING HEC-RAS SOFTWARE

Abstract

Board-crested weirs serve as an effective device for flow control and measurement, having a less complex geometry and offering an ease of operation and maintenance. unlike larger and elaborate hydraulic structures like dams and spillways, crested weirs allow the hydraulic engineers to gain appreciable control on regulating the water level in rivers and streams. Having a relatively simpler and more predictable head- discharge relationship, broad-crested weirs can be calibrated easily using modern computational softwares like HEC-RAS AND ANSYS fluent that carry out numerical simulation to predict the flow characteristics of the weir. Here in this study, experiments were performed on two shapes, one having vertical faces and other with sloped faces. A 4.0 m long, 30.0cm wide and 50.0 cm deep rectangular tilting flume with an adjustable channel was used to carry out 24 discharge runs in two configurations: horizontal channel bed and at a slope of 2%. Using the basic parameters from the experimental data as input values, numerical simulations were carried out on HEC-RAS and ANSYS fluent software programs. The data obtained from both the computational approaches were used to validate the experimental results. While HEC-RAS offered and ease of data input and lesser computation time, ANSYS fluent gave more consistently accurate values of water surface elevations and discharge relative to the experimental data.