FLOW CHARACTERISTICS OF NON - RECTANGULAR SIDE WEIRS

Abstract

Side weirs are being used extensively in irrigation, land drainage, urban drainage and flood protection works. Only rectangular: side weirs have been extensively studied in the past. The present study is an experimental investi-gation on the flow characteristics of non-rectangular side weirs, namely, trapezoidal, parabolic and circular side weirs installed at the head of a side channel taking off at 900, under subcritical flow condition in the main channel and free flow condition in the side channel. The basic spatially varied flow equation has been adopted to obtain the relations for the discharge over the above non-rectangular side weirs in terms of relevant geometric and hydraulic parameters. The important dimensionless parameters affecting the value of discharge coefficient CM are found to be Froude number Fr, angle of the weir e/2 (in case of trapezoidal side weir), shape factors A/B2 (in case ofparabolic side weir) and D/B2 (in case of circular side weir). The effect of these parameters on CM has been studied and relations have been proposed between CM and Fr fty all the above shapes of side weirs.