Author(s): Hubert Chanson
Linked Author(s): Hubert Chanson
Keywords: Open channel hydrodynamics; Sidewall longitudinal rib; Secondary flows; Physical modelling; Sedimentation;
Abstract: Channels with streamwise ribs have been studied for decades in chemical engineering, environmental and sanitary engineering, aeronautics, astronautics, biology and geology. Recently a biological study suggested that lateral longitudinal beam might assist with the upstream passage of small-bodied fish in hydraulic structures. Herein a detailed hydrodynamic study was conducted in an asymmetrical rectangular channel equipped with a sidewall square (50mm別50mm) rib in a culvert barrel channel. Both free-surface, velocity and boundary shear stress measurements showed strong secondary currents of Prandtl's second kind. The sidewall rib and channel asymmetry contributed to intense secondary motion, associated with turbulent dissipation. The channel design provided a small well-defined highly-turbulent low-velocity zone (LVZ) beneath the rib. In the context of hydraulic structure designs, uttermost care must be considered because of manufacturing, installation and operational issues. In many instances, alternative designs should be preferred to assist with fish passage in hydraulic structures. Altogether this detailed investigation demonstrated how the introduction of a seemingly simple streamwise shape, i.e. a sidewall square rib, may induce a major change in hydrodynamic properties, in comparison to a simple rectangular channel flow.