Laboratory Studies on Bed Form Effects on Water Surface Profiles in Side ‎Weirs

Side weirs are widely used to divert water from rivers. In movable bed rivers, deposition of sediment particles along the side weir may cause some problems in diverting water. This research is done in a laboratory flume of 0.9 meter wide and 10 meter long with a longitudinal slope of 0.001. Three value of weir length i.e. 0.6, 0.4 and 0.2 with a single weir height of 0.08 meter were used in the experiments. The variations of water surface profiles along the side weir were measured for various upstream Froude Numbers. 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 does effect on the water surface profile over the weir and thus changes the diverted flow discharge. Water surface and discharges over the side weir were found in good agreement with the results obtained from the analytical solution in compare with the results obtained from channel with movable bed. The computed relative error for flow discharge in channels with movable and rigid bed is 6.35% and 24.18% respectively. This amount for variations of water surface profiles along the side weir is 8.03% and 9.88% respectively.