wcm.01.2026.220.229

Improving energy dissipation and efficiency in hydraulic structures such as spillways, sluices, and weirs, is important to prevent downstream erosion and structural damage under high velocity (supercritical) flows. However, conventional stilling basin designs often fail to optimize hydraulic jump characteristics, particularly under strong hydraulic jump conditions. This study experimentally evaluates the hydraulic performance of single sill and double sill configurations of stilling basin in a laboratory-scale stilling basin under strong hydraulic jump conditions (11 < F_{1} < 13.2) A series of physical model experiments was conducted by varying sill geometry, height, and spacing. The results showed that the double sill configuration in Series DS-5, combination of an ogee sill (Z_{1} = 6cm) and a trapezoidal prism sill (Z_{2} = 4.5cm) spaced at L_{1} = 80 cm, L2 = 0.5L1 (40 cm), provides superior hydraulic performance compared to single sill and horizontal apron configurations. Series DS-5 achieved the lowest y2 and yj, the highest relative energy dissipation ((Eo-E2)/Eo = 81.42%), and average energy efficiency (E_{2} / E_{1} = 51.31%) The enhanced performance is attributed to intensified turbulence interaction and improved hydraulic jump control induced by combined sill geometry. Regression based relationships between dimensionless hydraulic variables were also developed to support predictive design. This research contributes a practical and compact stilling basin design for high energy flow conditions, offering improved efficiency and potential application in hydraulic structure design.