Hydraulic characteristics of trapezoidal baffle block with varying inclination angles set on stepped energy dissipator

In order to enhance the energy dissipation performance of stepped spillways and reduce the negative pressure zone, a composite energy dissipator was proposed by setting trapezoidal baffle blocks with different inclination angles (45°, 50°, 56°, 63°, and 72°) on the step edges (convex corners). The hydraulic characteristics of the composite energy dissipators under various flow rates were investigated through hydraulic model tests and numerical simulations, and compared with those of traditional stepped spillways. The results show that as the flow rate increased, the flow pattern gradually transitioned from a transitional flow to a fully developed skiing flow. The flow velocity along the chute was generally higher in the upper section and lower in the lower section. The high-velocity zone gradually merged into a continuous linear pattern and extended downstream. The boundary between high- and low-velocity areas became increasingly distinct, with the high-velocity flow becoming more concentrated and stable. The pressure at the concave corner of the steps initially decreased and then increased along the flow direction. For steps set with baffle blocks, the pressure at the concave corner was higher compared to steps without blocks. Negative pressure in the baffle-block sections occurred primarily at the top and rear surfaces of the blocks, whereas at sections without baffle blocks, negative pressure appeared at the convex corners of the steps. The negative pressure zone in the composite dissipator was smaller than that in the traditional stepped spillway. The influence of the trapezoidal baffle block inclination angle on the energy dissipation ratio first increased and then decreased, the overall energy dissipation performance reaching its peak at an inclination angle θ=50°.