Effect of gate weight on head discharge relationship of a regulator with gravity flap

Abstract

Regulator may defined as a hydraulic structure consists of piers at regular intervals arc generally constructed across the channel to control the flow. These structures an: capable of both draining out water from the catchment and entering water from riverside. In Bangladesh, Bangladcsh Water Development Board [s the Governmcnt Organization mostly responsible to build these kind of hydraulic structure for irrigation, flood control and drainage. Khulna-Jessore Drainage Rehabilitation Project is one of the large projects of BWDB having 20 drainage regulators consist of 2-21 vents. These regulators were constructed mainly on the basis of the head discharge relationship obtained from the theoretical equations. Proper operation and performance of these regulators can be ensured with accurate head-discharge relationsllip. As the co-efficient of contraction plays a sensitive role in computation of discharge, drainage may vary signif~cantly from the actual discharge in case of poorly judged contraction values. In this regard head-discharge relation was developed through a scale model of Sholmari regulator which is to constructed. Also the effect of gate weight in head-discharge has been investigated. With the model of Sholmari regulator a total of sixty-four test runs were constructed for different gate weights and discharges in the Hydraulics and River Engineering laboratory, WRE, BUET. The f1ume was calibrated with respect to a rehbock weIr placed at the tail end of the flume before the experiment was started. Head-loss discharge relationship for different weight of flap has been developed. From the analysis it has been found the experimental result significantly differ from the theoretical results. To have good matching of the computed results with the theoretical results some modifications have been proposed. These modifications are proposed in contraction of co-efficient as well as in area computation. The proposed values of co-efficient of contractions are ~l2= 0.70 and ~l4 = 1-0.20 cos<p instead of ~l2 = 0.5~ - 0.70 and )..1-4= 1-0.35 cos<p respectively. In area computation As = 1.5 Aycnt is proposed instead of As = 2 Aycnt. The measured discharges were found to vary within the range of 12% to 23% than the theoretical discharges. But with the proposed modified equation discharge were found to vary within the range of 0.16% to 6.3%.