Characteristics of the flow field within a developing scour hole at a submerged weir
Wen Zhang, Lu Wang, Bruce W. Melville, Dawei Guan, Colin Whittaker, Asaad Y. Shamseldin
Abstract
Local scour is an important design factor for submerged weirs. This study conducted a clear-water scour experiment at a submerged weir, using the particle tracking velocimetry technique to measure the flow field in the developing scour hole. The mean flow patterns, turbulence intensities and near-bed Reynolds shear stresses in the scour hole at different scour stages are presented and discussed. The submerged weir alters the mean flow significantly, forming a high-velocity zone above the weir and a vortex system near the scoured bed. As the scour develops, the high turbulence intensity zone and the high near-bed Reynolds shear stress zone both get closer to the upstream slope, and further away from the downstream slope of the scour hole. At the equilibrium stage, although the near-bed Reynolds shear stress near the upstream slope of the scour hole exceeds the critical shear stress of sediment entrainment, sediment moves in a recirculating form such that the scour hole does not further enlarge.