Author(s): Jun Deng; Wangru Wei; Zhong Tian; Faxing Zhang
Keywords: Ski jump; Dam; Outlets; Flip bucket; Spillways
Abstract: Given the enormous flow velocity, large discharge rate, and narrow valley conditions, the common ski jump does not apply to flood discharge and the energy dissipation safety becomes a key issue in high dam engineering. The conventional slittype flip bucket, using the design of side-wall contraction, results in high hydrodynamic pressure on the sidewalls, which is extremely dangerous to outlet structure. Based on research about motion characteristics of high speed flow, it is proposed that a leak-floor (dovetail shape) flip bucket is designed during the Jinping spillway construction. When water flows through the leakfloor area, the middle of the water is lifted into the atmosphere first and the natural pressure difference at lateral direction generates, making the water deflect transversely to the center-line simultaneously. This specific flipping action makes the water jet narrow-long, without high pressure on the side walls of the flip bucket. This design of leak-floor flip bucket improves structure safety and has been successfully applied to spillway outlet design with approximately 50m/s flow velocity. Based on physical model experimentation, the following items were addressed: (1) typical flow pattern of ski jump along the leak-floor flip bucket; (2) jet trajectory affected by the type parameters of flip bucket; and (3) pressure distribution on side-wall of flip bucket. Further, a comparison with previous results indicates a favourable behaviour of this flip bucket design for high-speed outlet.