DISCHARGE CHARACTERISTICS OF RADIAL GATES

Abstract

Development of suitable control equipment is required for both the conduits (including sluices and penstocks) and the spillways. The control equipment used includes various types of gates. Radial gates are the most often used control equipment. But before installing the gates their discharge characteristics should be studied in advance. Various studies have been made by different researchers on the hydraulic behaviour of different types of the gates. But there is not much information available about the discharge characteristics for partially and / or fully opened radial gates. Also under certain scenarios only the end or side bays of a spillway may be in operation, the flow from upstream to which shall be asymmetrical. Effect of asymmetry on discharge characteristics of the outlets is also not well known. The present study, therefore aims at providing such information investigated through well controlled experiments carried out on a sectional model of spillway of Shahpurkandi dam in Punjab. Experiments were conducted in the spillway model, in which there are three bays present, but one of the side (end) bays was however always kept closed. The width and height of each gate opening was 0.265 m and 0.144 m respectively. Spillway above these opening was covered with concrete breast walls, thus orifice flow mostly occurred through the openings. The experimental data collected in the present study was analysed for determination of the effects of asymmetry in. approach flow on characteristics of outflow through the spillway and for studying the variation of coefficient of discharge of the gate opening. it has been observed through analysis that due to asymmetry of the approach flow, the flow characteristics of the side (end) bay are different as compared to that of the central bay. The values of coefficient of discharge Cd were observed to be highest for the central gate and to be the lowest for the side (end) bay, but the coefficient of discharge, Cd values were in between the above two when both bays were in operation simultaneously. Different relationships are proposed for determination of Cd values while the different bays were in operation for full and partial openings. The functional form of the proposed relationships have physical basis and these are found to produce good results when validated with the observed data. iv