Optimising round-edged entrance of 55° river water intake

An experimental study was undertaken to optimise a 55° round-edged entrance irrigation water intake. The tests were carried out under different flow conditions in a laboratory flume with a rectangular cross-section under close-ended and open-ended flow conditions. To improve the efficiency of water intake, its entrance was rounded with three different radii (r): 100, 150 and 200 mm. Two components of flow velocity in transverse and flow directions were measured using an electromagnetic velocity meter. The flow velocity inside the water intake was measured at 390 regular grid points, across three horizontal layers at 30, 60 and 120 mm heights from the bed. The streamlines were drawn from the captured flow velocity, and hence the separation width and length were determined for the different depth levels, from the bed to the water surface. The discharge ratios (Q_r) of the main channel to the lateral channel were set equal to 0·25, 0·67, 1·5 and 4. It was found that a 55° water intake with the radius of curvature of r/W_b = 0·8 produced minimum separation size. It was therefore selected as the optimum 55° round-edged entrance water intake.