In this paper, the application of NACA airfoil pillar-shaped flumes and the influence of their wing lengths on flow measurement characteristics are discussed. The standard k-ε three-dimensional turbulence model and the volume of fluid (VOF) method were used for numerical simulation of the flow in six NACA airfoil pillar-shaped flumes with different wing lengths. In addition, to verify the accuracy of numerical simulations, the corresponding experiments were conducted. The Buckingham Pi theorem of dimensional analysis coupled with the incomplete self-similarity theory was applied to deduce the theoretical flow calculation formula of these flumes. Moreover, Froude number, velocity distribution, backwater height, critical submergence, and energy loss of the flume were analyzed, for which the experimental and numerical results are compared and further discussed. The results show that the backwater height is directly proportional to the wing length, while the head loss and critical submergence are inversely proportional to the wing length. Based on the results, in terms of backwater height, it is recommended to use the NACA airfoil pillar-shaped flume with a smaller wing length, while, in terms of head loss and critical submergence, the NACA airfoil pillar-shaped flume with a larger wing length should be used.

Leaky barriers serve as a soft-engineering approach for river management and have become indispensable for river restoration and bank stabilization. In this study, we idealized multiple full-span leaky barriers as horizontally arranged cylindrical arrays with uniform diameters (d) and equal spacing (0.5d). Flow field visualization was conducted using tracer techniques, and particle image velocimetry was employed to quantify the effects of blockage ratio on wake structures behind these barriers. Results demonstrate that flow deflection induced by barrier obstruction generates a primary jet through basal gaps. The maximum velocity of the primary jet (u¯max) increases with the blockage ratio (ψ), reaching 2.82–4.43 times the average velocity of the incoming flow (U0). The primary jet retains initial velocity at x/d≤0.5, decaying linearly within 0.5<x/d<2.4. Within 2.4<x/d<8, the decay rate diminishes due to jet merging and weakened adverse pressure gradient. Multiple secondary jets emerge within inter-cylinder gaps and are deflected by the low-pressure zones downstream of cylinders. These jets coalesce before merging with the primary jet. Coherent vortex bands with elevated vorticity develop near wake shear layers, significantly enhancing turbulent kinetic energy in these regions. Jet interactions modulate velocity decay patterns in both primary and secondary jets. This work reveals fluid-barrier interaction mechanisms, advances hydrodynamic understanding of leaky barriers, and evaluates their ecohydraulic implications for riverine ecosystems.

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.

Based on the principle of the critical flow and standard k-ε three-dimensional turbulence model, experiments and simulations were performed on a portable pillar-shaped flume with three contraction ratios under 12 working conditions. By combining the numerical simulations with the experiments, the theoretical stage-discharge formula of the portable pillar-shaped flume was developed, and the variations in the Froude number, backwater height, critical submergence, head loss, and velocity distribution were examined. The simulation data obtained from the standard k-ε three-dimensional turbulence model are in good agreement with the experimental results, with a maximum error of 8.65%. The maximum error in the difference between the theoretical stage-discharge formula and the measured value is 4.74%. The upstream Froude number is less than 0.5, and critical submergence is between 0.73 and 0.96. Compared to airfoil pillar-shaped flumes, the portable pillar-shaped flume had a significantly smaller head loss and backwater height. Finally, the portable pillar-shaped flume can be used for flow measurement and has the advantages of high measurement accuracy, low backwater height, and small head loss.