Author(s): Zhiyong Dong
Linked Author(s): Zhiyong Dong
Keywords: Pool-weir fishway; Velocity distribution; Turbulence intensity distribution; Reynolds stress distribution;
Abstract: Fishways can assist fish species to overcome obstacles for performing spawning, feeding and overwintering migrations. Flow structures in a pool-weir fishway 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 Hydraulics Laboratory at Zhejiang University of Technology. Two typical flow rates (Q1=20.79L/s, Q2=30.04L/s) corresponding to detection and preference velocities of fish species were considered. The 5 different depths for each flow rate were taken, whose spacing was 10cm. 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 distribution along flow depth, Reynolds stress distributions on different planes of flow depth and on different cross-sections in the pool of fishway were analyzed. The experimental results showed that distribution of longitudinal velocity was characterized by topology, which constituted considerable vertical vortex. Weir flow after plunged the pool flowed along surface layer in the form of skimming flow. Peak-value range of longitudinal turbulent intensity existed. Amplitude of variation in Reynolds stress near surface layer reached the maximum, which provided hydraulic condition for fish that favor jumping near surface layer.