On the interaction of fish and marine hydrokinetic turbines: Insights gained through experimental and computational observations

Tidal and riverine hydrokinetic turbines offer promising solutions for renewable energy generation in aquatic environments. However, their ecological impact, especially on fish behavior, warrants a thorough investigation. This study presents an integrated experimental and computational analysis of fish turbine interactions, combining laboratory observations with high fidelity large eddy simulations. The simulations capture essential flow features, including wake asymmetry, vortex shedding, and spatial variations in turbulence intensity, under varying flow and rotational regimes of a geometry resolved vertical axis turbine. Behavioral experiments with rainbow trout reveal a consistent tendency to avoid high turbulence and high shear regions, favoring low turbulence zones such as downstream sidewalls. Hydrodynamic stressors and energetic demands were characterized using turbulence metrics, including turbulence kinetic energy, Reynolds stress, and integral length scale, along with estimations of fish generated thrust force. Our results demonstrate that turbine induced turbulence significantly influences fish movement and habitat selection, highlighting the need to consider behavioral responses in conventional fish injury assessment frameworks. These findings provide critical insights for designing and operating hydrokinetic turbines in ecologically sensitive waters, ensuring a balance between renewable energy extraction and aquatic ecosystem protection.