Experimental Investigation of Incipient Motion of Sediment in a ۱۸۰-Degree Bend

Channel curvature and river meanders significantly influence sediment motion, making it vital to predict incipient sediment motion for effective river restoration. The research involved measuring ۸۴ velocity profiles at flow depths of ۱۳, ۱۵, and ۱۷ cm, both along a straight path and at a ۱۸۰-degree bend within a laboratory flume. This study also proposes a criterion for examining the sediment motion threshold in river bends. The results reveal that channel curvature influenced the velocity distribution around the sediment movement threshold. The findings show clear spatial differences in longitudinal velocity across the channel. Velocities increase towards the outer bank, with distribution patterns differing between the upstream and downstream parts of the bend. The critical Shields parameter at the bend was about ۸-۶۱% lower than suggested by the Shields diagram, decreasing from ۰.۰۴۲ at the start to ۰.۰۱۶ at the end of the bend. This reveals that no single value should be applied in the incipient motion projects because no universal value exists, but it should emphasize the defendable values in the fluvial studies

کلیدواژه ها:

velocity distribution ، incipient motion of sediment ، ۱۸۰-degree bend ، Shields parameter ، bend channel