Innovative configuration of vertical slot fishway to enhance fish swimming conditions

A vertical slot fishway (VSF) is among the most effective and commonly used fishway structures to enable fish to pass through artificial barriers such as dams and weirs in the river. Nevertheless, such structures need further improvements in providing better swimming conditions for fish inside the pool and enhancing attraction at the entrance. Therefore, the main objective of this study was to investigate the influence of slope and whether integrating some cylinder structures inside the fishway could enhance further attraction and provide better swimming conditions for fish. This study consists of several numerical simulations, first considering the fishway without cylinder elements while testing three different slopes under two different discharges. Then, the same numerical simulations were conducted, considering cylinder elements of different diameters and arrangements inside the fishway. The numerical model was validated by comparing computed velocities with those measured experimentally from the literature. The results show that the maximum velocity and turbulent kinetic energy (TKE) in the main jet increase as the discharge increases on the same slope. The flow velocity and TKE decrease in the areas inside the pool and between the two baffles. Introducing cylinder elements inside the fishway reduces the principal flow' s maximum velocity. Also, inside the pool, low-velocity regions were expanding. A comparison between the design with a cylinder and the simple VSF indicates that the presence of a cylinder reduced the maximum velocities for the smallest and highest slopes by 6.21% and 9.86% on average, respectively. However, in terms of TKE, cylinders inside the fishway could provide better performance than simple VSF, mainly for low-flow conditions. Finally, this study's solution-oriented findings provide insights that could help design cost-effective fishways by improving particularly fish attraction to the fishway.