Author(s): Yuji Hara, Akihiro Tominaga, Yuka Kuno, Naohiko Sassa
Linked Author(s): Akihiro Tominaga
Keywords: Local scour, narrowed section, bed shear stress, clay layer, platform vortex
Abstract: A large scoured area with 20 m depth in maximum is observed besides the convex river bank in the Kiso River. Expanding of the scour has possibility of causing destabilization and damage to hydraulic structures. It is necessary for river control and maintenance to make clear the generation mechanism of such a deep scouring. We consider the effect of narrowed section in a river as a trigger of scouring. In this study, we investigate the flow and bed deformation around a narrowed section in an open channel and then the flow structures around a deep hole in an open channel experimentally and numerically. Particularly, to model an erosion proof clay layer, sand was solidified partially with resin spray. The bed shear stress becomes higher so as to erode the clay layer at the center of channel in appropriate condition of the contraction ratio. Finally, scour hole similar to the field observation was reproduced in the laboratory channel. The characteristic flow structures that include vertical and transverse vortices were indicated. It is suggested that these flow structures have potential to maintain and develop the scour hole
Year: 2017