Investigation of Free Flow Characteristics Beneath a Vertical Sluice Gate Featuring a Positive Step in a Radial Stilling Basin

To control water flow, vertical sluice gates are frequently used in drainage and irrigation systems. It is possible to place these gates in prismatic or non-prismatic channels. In stilling basins, steps may be constructed depending on site topography and design criteria, primarily to enhance energy dissipation and reduce the hydraulic jump length. The current study focuses on examining how a positive step located within a radial stilling basin affects discharge characteristics under free-flow conditions beneath a sluice gate. An experimental setup featuring a diverging channel with a fixed length and a constant divergence angle was used. The influence of various relative heights and placements of the positive step on the sluice gate's discharge coefficient was thoroughly explored. Additionally, the study assessed how replacing vertical steps with sloped steps impacts discharge behavior. Through dimensional analysis, a relationship between the discharge coefficient and flow/step parameters was established. The results indicate that incorporating a positive step downstream of the gate in a radial stilling basin enhances the discharge coefficient, with even greater improvement observed when sloping steps are used. However, the gain in discharge efficiency diminishes as the step is placed farther downstream. Using multiple regression analysis, dimensionless equations were derived to estimate the sluice gate discharge coefficient as a function of flow and geometric parameters.