Author(s): Seyed Ali Ayyoubzadeh; Mehdihabibi; Mohammad Rostami; Mojtabasaneie; Mohammad Faramarz
Linked Author(s):
Keywords: Lateral overflow structure; River-bed form; Channel with moving river-bed; Water level profile
Abstract: Side weirs are widely used in rivers and irrigation and drainage systems to divert water from main channel. In movable bed rivers, deposition of sediment particles along the side weir may cause some problems diverting the water. In this research, variations of water surface profile over a rectangular side weir are investigated. The study has been done in a 0. 9 meter wide and 10 meters long laboratory flume with a longitudinal slope of 0. 001. Three ratios of weir length to flume width (i. e. 0. 67, 0. 44 and 0. 22) with a single weir height of 0. 08 meter were used in the experiments. The median diameter of selected bed material was equal to 0. 23 mm. The variations of water surface profiles along the side weir and along the center line of the flume were measured for various upstream Froude Numbers. The channel bed profile along the side weir was measured in each test and indicated that water surface profiles were out-of-phase with the bed form profiles along the weir and main channel. The obtained results from experiments on movable bed condition were compared with those from rigid bed condition and also with the results from analytical solution. The results showed that bed form made by flow regime in the vicinity of the side weir has some effect on the water surface profile over the weir and thus changes the diverted flow discharge. Water surface was raised over the side weir where the deposition of sediments occurs along the side weir which in turn changes weir discharge coefficient that is needed to design the weir geometry. Water surface profiles and side weir discharge in the channel with rigid bed were found in good agreement with the results obtained from the analytical solution. The Relative Error (RE) percentages between the measured data and analytical solution for weir discharges ratio (Qd/Q1) in rigid and movable bed channel are 0. 14% and 0. 54% respectively. These values for the energy ratio (E/E1) along the side weir are 1. 28% and 1. 37% respectively.
Year: 2013