Effect of triangular baffle designs on flow dynamics and sediment transport within standard box culverts

Abstract

The placement of baffles in culvert structures has a significant impact on local hydrodynamics and sediment transport, which are essential for improving fish passage and enhancing aquatic habitats. Large eddy simulations (LESs) are performed to study the influence of triangular baffle designs on flow structure and sediment transport in standard box culverts with varying baffle sizes and spacings. The Reynolds numbers based on the baffle size for these conditions are 37 778 or 75 012. The LES method is validated using experimental data of mean streamwise velocities, and a good agreement is achieved. The simulations demonstrated that the presence of baffles with various designs significantly altered the flow field in their vicinity. Various distinct flow features, such as separation zones, recirculation zones, and resting zones (RZs), are captured. The RZ and low positive velocity zone (LPVZ) show a positive correlation with the baffle size in the culvert, while the negative velocity zone (NVZ) exhibits a negative correlation. The flow field is primarily characterized by a large recirculation zone between the baffles, with the baffle size being the predominant influencing factor. The spacing between the baffles partially constrains the extension of the recirculation zone. The range of turbulence parameters, including the turbulent kinetic energy (TKE) and Reynolds shear stress (RSS), expands as the baffle size increases and the baffle spacing decreases. The presence of baffles suppresses ejections and sweeps interaction turbulence events downstream of the baffles. The near-bed coherent structures are responsible for the erosion zone between the baffles.