Analysis And Optimization of Hydraulic Characteristics at Fish Guidance Structures Using CFD

Abstract

Mechanical behavioural fish guidance racks (FGR) with vertical bars are a promising technical solution for the safe downstream movement of fish at run-of-river hydropower plants (HPP) and water intakes. They do not pose a physical barrier to most fish but rather create flow patterns that deter fish from passing the bar rack and guide them towards a bypass system. Current knowledge of flow parameters that induce this avoidance behaviour is limited. Furthermore, FGR may impair the energy production and operation of HPP as they generate additional head losses and affect the turbine admission flow through deflection of the current. In order to provide a widely applicable and robust solution, a balance between effective fish guidance and minimal hydraulic losses needs to be found. In this study, a computational fluid dynamics (CFD) approach is used to efficiently test and compare different bar shapes and their impact on the flow field both upstream and downstream of the FGR. The results show that the use of hydro-dynamically shaped bars significantly improves the hydraulic performance of the rack. Furthermore, the study proves that CFD modelling is a valuable tool for this kind of analysis as parameters can easily be adapted and the results can be obtained in high spatial and temporal resolution.