Investigation of Live-Bed Scour at Labyrinth Side Weirs

Side weirs, also known as lateral weirs, andoverflow dams are free overflow regulation and diversion devices commonlyencountered in hydraulic engineering. The lateral loss of water is reducing thesediment transport capacity in the main-channel and the formation of a localsediment deposit in the downstream of weir. The head over the side weir risesand the side overflow discharge as well. The design discharge to be divertedover the weir is increased by this flow-sediment transport interaction. Althoughthere were no studies that scrutinized the scouring depth and geometry thatoccurs around the labyrinth side weirs in channels with movable bed, there arelimited number of studies that examined the scouring geometry around theclassical side weir. In the present study, local scour depths formed in theperiphery of triangular labyrinth side weir mounted in a live-bed rectangularcross-section straight channel were experimentally investigated under steadystate flow and free overflow from the side weir conditions. To provide forlive-bed conditions, the sediment was added to bed material in the experiments.A series of experiments were conducted for live-bed scouring conditions (forflow intensity greater than one) to determine the maximum scour depths that occuraround the triangular labyrinth side weir with different flow depths, differentmain channel discharges, different volumetric amounts of sediment feed,different crest heights, different Froude numbers, different flow intensitiesand using uniform bed material. In the experiments, the dimensions of thescours and sediment deposits that occur upstream and downstream of the weirexhibited a periodic change (increase and decrease). The maximum depth of scouroccurred at the downstream end of the triangular labyrinth side weirfrequently.