Particle tracking to assess safe fish transport through closed conduit components

Fish travelling through closed conduit systems experience a range of hydrodynamic effects which can influence fish wellbeing and consequently ecological restoration and conservation outcomes. Computational Fluid Dynamic (CFD) models are a promising tool for assessing such effects to improve fish safety. In this study, Lagrangian sensors were used in a physical model, systematically testing hydrodynamic conditions in pipe components in conjunction with live fish tests of Australian silver perch (Bidyanus bidyanus) to determine safe fish transport thresholds and fish travel paths. CFD models of pipe components were validated using the Lagrangian sensor data and Discrete Phase Model (DPM) particles with good agreement of pressure and acceleration data. The implementation of a simple active particle function to represent fish movement greatly improved the particle paths in the model, matching trajectories of live fish transported through the pipe components. Utilising active paths, the CFD models identified additional hydrodynamic threshold values to prevent fish injury. CFD modelling of larger pipes suggested that closed conduit fish passage through full-scale pipes present similar risk to laboratory-scale tests. These findings show that CFD models will assist the sustainable design of closed conduit fishways, which can improve river connectivity.