Author(s): Youichi Yasuda; Shintaro Narazaki
Linked Author(s): Youichi Yasuda
Keywords: Submerged hydraulic jump; Artificial control; Periodical deflected flow; Diagonal baffle blocks; Upstream migration route
Abstract: If a submerged hydraulic jump has a large submergence, a high velocity flow below a sluice gate is located near the bottom. When the main flow lifts to the water surface from the channel bottom, at a certain condition, the main flow is periodically deflected. In this case, it might be difficult for swimming fishes to migrate upstream through the hydraulic structure, even if the fish passage is installed at the downstream of the structure. Because, most of swimming fishes might lose their upstream migration route by the formation of the periodically deflected flow. In this study, the installation of diagonal baffle blocks at the downstream of a sluice gate was proposed in order to disappear a periodically deflected flow in submerged hydraulic jump. The velocities and flow condition in the improved submerged jump were investigated experimentally. It has been confirmed that the main flow is concentrated into center part by installing diagonal baffle blocks properly at both side below sluice gate, and the periodically deflected flow can be changed to a stabilized flow. The artificially controlled flow has been characterized by the time averaged velocity vectors and the distribution of turbulent intensity. The velocity distribution at vertical section yields that the main flow is controlled by the installation of baffle blocks. Also, the change of velocity with time series shows that the fluctuation of the main flow can be reduced by the disappearance of the periodically deflected flow.
Year: 2020