Practical application of CFD for fish passage design

ABSTRACT

There is a growing demand of waterway barriers for uses like irrigation, recreation, mining, public access, climate resilience and energy. This demand often negatively impacts quantities of native Australian fish and the health and biodiversity of their ecosystems by reducing their catchment. Fishways are critical to the survival of Australian fish by reducing the impact waterway barriers have on their movement. The design of these, especially for larger barriers and weak swimming fish is technically complex, with Fisheries Scientists reliant on good modelling to inform on fish attraction and passage performance. When dependent on modelling outcomes, poor modelling practices inevitably lead to poor fishway performance, this being primarily measured with monitoring reports of fish quantities. Hydraulic modelling is rarely validated post construction of fish passage meaning poor modelling practices are often not corrected. A computational fluid dynamic (CFD) model was developed of a generic fishway key-hole vertical slot constructed in rural Australia using FLOW-3D and compared against recorded water depths and video footage. Development of the model included a detailed literature review and broad sensitivity testing of common model parameters to better understand their influence on water depths, velocities and turbulence. Results from the modelling demonstrate water depths and surface velocities consistent with the recorded data, also flow regimes and velocities consistent with the literature. Findings include parameters that were highly influential on flow vectors and suggestions to minimise their impacts.