Hydraulic jump analysis: Influence of negative steps and end sills on jump profile for both smooth and Dunal corrugated beds

Hydraulic jumps are the key mechanism for energy dissipation downstream o spillways; nevertheless, the intense near-bed velocities they generate can contribute to structural wear and significant scouring downstream of stilling basins. Prior studies have examined the effects of bed roughness, negative steps, and end sills individually; their combined impact remains inadequately explored. This study numerically investigates six stilling basin configurations downstream of an ogee spillway, involving different combinations of smooth and dunal corrugated beds with and without negative steps and end sills. Numerical simulations were performed using FLOW-3D for a discharge of 15 L s−1. To validate the numerical model, experimental data were collected for a dunal corrugated bed configuration, showing strong agreement with simulation results. The analysis included longitudinal velocity profiles, streamline plots, water surface elevations, total energy lines, turbulent kinetic energy, turbulence dissipation, Q-criterion vortex dynamics, etc. The results reveal that a negative step significantly reduces near-bed and depth-averaged velocities, enhancing energy dissipation. The addition of the end sill further promotes flow stability. Among all configurations, the combination of a dunal corrugated bed with a negative step (Model 4) demonstrated the highest energy dissipation and the lowest water surface elevation. Roller length was shortest for the corrugated bed and longest for the smooth bed; however, adding a negative step and end sill increased roller length while improving turbulence control. Q-criterion analysis highlights dense, coherent vortex structures in Model 4, indicating efficient turbulence mixing and energy loss. These results underscore the value of integrating bed roughness with geometric modifications.