Numerical modeling of flow field at shaft spillways with the Marguerite-shaped inlets

By decreasing the entrained air flow discharge and improving the hydraulic characteristics of vertical shaft spillways, the Marguerite-shaped inlets can mitigate the effects of swirling flow surrounding their inlet. This study numerically investigates the hydraulic and hydrodynamic characteristics of flow around the Marguerite-shaped inlets under orifice flow regime, applying different geometrical parameters. This configuration of the inlet can decrease the strength of swirling flow and increase the flow discharge through the shaft. The finite volume method and the RNG k-ε turbulence model were employed to solve the governing equations of motion in a cylindrical coordinate system and a two-phase air-water flow on the water free-surface. Increasing the height and length of the blades of the Marguerite-shaped inlets was found to increase area of the barriers against the swirling flow, weaken the swirling flow strength, engender a more uniformed flow and lower the water free-surface level. Extremely long or high blades, however, causes an intense collision of the flow with the spillway and increases the water free-surface level and the swirling flow strength at the Marguerite-shaped inlets.