Abstract:Based on the hydraulic model test method, using the hydraulic model of the Yellow River Guxian Water Control Project with a geometric scale of 60, the characteristics of water jet and the pressure characteristics at the floor of the plunge pool of six flip bucket shapes were studied, including continuous, narrow-slit, differential, dovetail, straight edge narrow-slit dovetail and curved narrow-slit dovetail shapes. The experimental results show that the continuous flip bucket water jet has a continuous and concentrated form.The narrow-slit flip bucket of a 30° jet angle does not show a longitudinally stretched water jet shape, with a large internal and external edge trajectory distance and a small water inlet width, and the impact pressure and the fluctuating pressure intensity are larger. The differential flip bucket water jet presents the morphological characteristics of stratified and split strands, the water inlet width becomes larger, and the impact pressure and fluctuating pressure intensity are reduced. The dovetail flip bucket water jet is longitudinally shaped like a broom. The water jet has a large diffusion area, and diffuses, aerates, and dissipates friction fully in the air with a greatly increased water inlet width. No impact pressure occurs in the time-averaged pressure, and the maximum fluctuating pressure intensity is reduced by 59.5%, 69.8%, and 39.4%, respectively, compared with the continuous, narrow-slit and differential flip buckets. The horizontal contraction and longitudinal stretching effects of the curved narrow-slit dovetail flip bucket is better than that of the straight-sided narrow-slit dovetail flip bucket, and the lateral contraction is conducive to the turbulence of the water near the dam and weakens the turbulence of the water in the second dam area. The dovetail flip bucket is conducive to the stability of the plunge pool floor and the downstream energy dissipation and erosion prevention. It has certain reference value in flip bucket shape selection for similar high gravity dams. Keywords: gravity dam; ski-jump energy dissipation; flip bucket shape; water jet characteristics; time-averaged pressure; fluctuating pressure 〖FL