An Experimental Study Of Turbulent Structures And Fish Movement In Weir-type Fishway

In order to connect the fish's migratory passages and maintain biological diversity,fish passages are usually set up in water conservancy hubs such as tidal gates,drainage gates,flood gates,and dams to achieve harmonious development of water conservancy projects and ecological environment.The fishway is a low-headed hydraulic structure that allows fish to overcome obstacles to achieve spawning,swimming,and wintering.The effect of the fish pass is not only related to the hydraulic characteristics of the fish pond,but also depends on the fish's traceability.According to research data,there are still less than half of the fish passes that can be traced through the fish passes that have been built around the world! Therefore,it is of great practical significance to further study the hydraulic characteristics of fish passes based on fish migration habits,especially the mechanism of fish turbulence structure affecting fish migration.Turbulent structures and fish movement in flat-crested and notch-crested weir-type fishways were experimentally studied,which mainly contain variation of longitudinal time-averaged velocity along flow direction and its distribution along flow depth,distribution characteristics of vertical time-averaged velocity,flow pattern on longitudinal profile,turbulence intensity distribution and Reynolds stress distribution and their variation in flow rates.The experimentations were carried out in a large scale fishway model in the Laboratory of Port,Waterway and Coastal Engineering at Zhejiang University of Technology.Two typical flow rates corresponding to detection and preference velocities of fish species were considered.The 5 different depths for each flow rate were taken,whose spacing was 10 cm.The 11 transverse lines with spacing 5cm were arranged for each plane.The 10 measuring points with spacing 5cm were laid along each transverse line.Three-dimensional velocity at each measuring point was measured by Acoustic Doppler Velocimeter(ADV).Longitudinal and vertical time-averaged velocity distributions,longitudinal turbulence intensity distribution on different planes of flow depth,vertical turbulent intensity distributionalong flow depth,Reynolds stress distributions on different planes of flow depth and on different cross-sections in the pools of flat-crested and notch-crested weir-type fishways were analyzed.In addition,swimming behaviors of target fish in the fishway were observed by high speed photography based on the fish tests with implanted T-shaped tag.Reaction and detection of target fish to instant and would-be swimming environment as well as relation with turbulent structures in flat-crested weir-type fishway were analyzed.