Turbulent flow around a sidewall triangular baffle in a culvert under varying baffle orientations

Large-eddy simulations (LESs) were performed to investigate turbulent flow past a triangular baffle in a culvert at three orientations of 45°(C45), 90°(C90), and 135°(C135). The Reynolds and Froude numbers were fixed at Re=70 000 and Fr=0.376, respectively. The LES approach was first validated against laboratory measurements of mean velocity and turbulence intensity, showing good agreement. The time-averaged velocity fields indicate that the blockage effect decreases with the increasing baffle angle, with high-velocity regions concentrated near the baffle in C135. Flow separation produces recirculation zones upstream and downstream of the baffle; the upstream recirculation disappears in C135, while the downstream zone shortens and weakens with angle and elevation. Reynolds shear stress and turbulent kinetic energy contours confirm that turbulence is strongest in the shear layer and most intense in C135. Instantaneous flow structures identified by the Q-criterion highlight coherent vortices and strong vortex shedding, particularly at larger baffle angles. Quadrant analysis shows a transition from a balanced distribution of turbulent events in C45 to dominant ejection–sweep interactions in C90 and C135, accompanied by increased fluctuation intensity. Spectral analysis reveals vortex-shedding frequencies of 0.196–0.296 Hz, corresponding to Strouhal numbers of 0.055–0.083, which increase with baffle angle.