Author(s): Zhipeng Yuan; Saiyu Yuan
Linked Author(s): Saiyu Yuan
Keywords: River confluence surface roughness particle image velocimetry secondary current separation zone
Abstract: Riverbed roughness is generally considered to inhibit the development of secondary flow in confluence. However, recently, strong secondary currents have also been observed in large-scale confluences with high roughness. This indicates that the detailed effect of roughness on confluence flow is still unclear. In this study, laboratory-scale confluence experiments were employed to investigate the response of flow features to different surface roughness. It is found that the gravel surface reduces the primary velocity at the confluence due to greater water depth. A smaller separation zone was observed over the gravel surface, causing a higher curvature of the tributary streamline. The higher curvature and water depth jointly contributed to stronger secondary current. However, in the case of gravel surface, the flow in post-confluence recovered faster due to the smaller separation zone, leading to a significant decline in the primary velocity. This, coupled with the high energy dissipation due to surface roughness, promoted the decrease of secondary current intensity.
Year: 2025