Time-averaged flow and turbulence characteristics induced by partially spanning vegetated leaky barriers

Partially spanning vegetated leaky barriers (VLBs) composed of large vegetative debris have become an effective solution for channel rehabilitation, stream stabilization, erosion control, and habitat restoration. Understanding the fluid mechanics of flow around VLBs is crucial for optimizing their design, accurately predicting their hydrodynamic effects, and evaluating their ecological functionality. This study employs an experimentally validated large eddy simulation approach to investigate the flow structures generated by VLBs with varying blockage ratios (0.1–0.5). Results demonstrate that, compared to a solid barrier, VLBs can suppress flow separation, attenuate turbulence, and reduce local scour. Through internal gap flows, VLBs inhibit the development of recirculation zones and lower turbulence intensity, reducing the recirculation zone length by 91% and decreasing the domain-averaged turbulent kinetic energy by approximately 64% relative to solid barriers. The power spectral density of lateral velocity fluctuations in the horizontal shear layer is substantially lower in VLBs. The cross-sectionally averaged turbulent kinetic energy decays more rapidly along the streamwise direction in VLBs. By distributing flow through their permeable structure, VLBs homogenize bed shear stress distribution and lower peak stress values. This work advances the understanding of fluid–barrier dynamics controlling leaky barrier efficacy, thereby informing the design of multi-functional structures that balance hydraulic engineering requirements with ecological restoration targets.