CFD analysis of bioenergetics metric at a step with horizontal cylinder

The flow over a step in an open channel can create complex flow patterns and recirculation zones. In this study, the impact of a cylinder located downstream of a step in a three-dimensional channel was numerically investigated using computational fluid dynamics (CFD). Such a cylinder placed at different locations downstream of the step can significantly affect the recirculation zone, leading to the formation of a second recirculation zone. In addition, the cylinder may have an impact on hydraulic complexity and turbulence levels in streams. In river ecology, habitat quality is correlated with the substrate and the flow characteristics, which are related to the hydraulic complexity within a stream. In this study, the bioenergetics metric M2, which approximates the drag forces imposed on aquatic organisms moving between two locations, was used to identify bioenergetics patterns in the flow over the step. The presence of the cylinder caused an increase in metric M2, suggesting that obstacles can significantly impact the local flow structure and thus potentially affect the availability of suitable habitats for aquatic organisms.