Fish damage assessment during the passage through traditional and fish-friendly axial-flow pumps with Lagrangian tracking approach

A large number of fish are prone to death during the passage through pumping stations according to the monitoring data, especially when the axial-flow pumps are equipped. This study comprises the assessment of fish damage for traditional axial-flow pump and the redesigned so-call fish-friendly pump. The Lagrangian tracking approach combined with computational fluid dynamics that takes the fish profile and contact force into account is used to shed light on the fish motion behaviors. The three most important mechanisms for fish injury (i.e. the strike of blade leading edge, pressure reduction and shear force) are discussed. Results show that the fish-friendly pump with reduced number of blades leads to sharp drop of strike probability and its spiral-shaped blade leading edges effectively alleviate the impact force. Pressure reduction and shear force are demonstrated to be severer in the domain of rotating impeller compared with other components, and numerically proven to unlikely pose a threat to fish survival at design condition. The present study offers the evaluation framework of fish damage in axial-flow pumping stations which can be applied to other aquatic organism, and on the other hand points to optimization design of pump to achieve the goal of ecological protection.