Influence of baffle block and weir downstream slope at stilling basin of solid roller bucket type on hydraulic jump and energy dissipation

Abstract

Weir is a water structure built crossing a river to elevate the water level or the channel that will be directed to the irrigation network. The rise in water level due to damming will result in rapid flow to downstream. The change of flow from supercritical to subcritical will create a hydraulic jump. In order to reduce the energy contained in the flow, it is necessary to build an energy dissipater, which is stilling basin. The purpose of this research was to know the influence of downstream weir slope and the influence of baffle blocks arrangement on hydraulic jumps and energy dissipation on the solid-roller bucket. The research was conducted at Hydraulics Laboratory of Civil Engineering Department, Faculty of Engineering, UMS. This study used an open flume with dimension of 30×60×1000 cm with a channel bed slope of 0.0058, an ogee spillway with a downward slope of 1: 4, 2: 4, 3: 4, 4: 4, and a solid-roller bucket stilling basin with baffle blocks of 5/12 R. The study was conducted on sixteen treatments (downstream slope and placement baffle blocks) wit h four variations of water discharge, in which the flow turbulence, the length of the whirlpool and energy loss of each discharge were tested. The results show some conclusions. First, the increasing flow triggers the greater turbulence, the length of hydraulic jump downstream of the vortex, and the smaller value of the percentage of energy loss. Second, the most effective baffle block arrangement in reducing turbulence and hydraulic jumps is the one that is placed at the center of the curved radius. Third, the efficiency of energy loss increases with reduced discharge variation, the treatment without baffle blocks is the most effective. Fourth, with the same flow rate of the downstream body weir variation, there is insignificant difference to the flow turbulence and energy loss except for the hydraulic jump length, which is the most effective 4: 4 slope.