Experimental and numerical investigation of energy dissipation in three-step gabion weirs with and without gabion end sill

Gabion weirs are porous hydraulic structures widely used for energy dissipation in low-head water control systems. Previous studies have investigated flow regimes, porosity effects, and hydraulic performance of gabion stepped weirs; however, the influence of a gabion end sill on energy dissipation has received limited attention. This study experimentally and numerically investigates the energy dissipation efficiency of a three-step gabion weir with and without a gabion end sill. Experiments were conducted for eight discharge conditions ranging from 0.016 to 0.044 m 3 s −1 . Flow behavior, energy dissipation efficiency, drop-number-based energy loss ratio, turbulence kinetic energy distribution, and velocity profiles were analyzed. Results indicate that the three-step gabion weir with a gabion end sill consistently provides higher energy dissipation, improving performance by approximately 1–3% compared with the conventional configuration. Numerical simulations show similar trends, although energy dissipation is overestimated by up to 5%. Turbulence and velocity analyses demonstrate enhanced and more uniformly distributed energy dissipation near the end sill, confirming its effectiveness in improving hydraulic performance.