Hydraulic Physical Experiments On Shape Optimization Of Allotypic Hybridtype Flip Bucket

With the implementation of the Great Development in Western China, the hydraulic engineering has been in the fields of high water head and large discharge per unit width, the selection of energy dissipation is becoming a focus topic. The Allotypic Hybridtype Flip Bucket (AHFB), which combines the traditional diffusion bucket with slit-type bucket, has the distinct characteristics of application. Data shows that the bucket can be widely applied not only to the side spillway with high-head and large-discharge per unit width, but also to the high arch dam in narrow valley. This paper mainly studies the shape optimization of AHFB by theoretical analysis and model test, based on the previous studies. The main contents of the studies and achievements are as follows:(1) Studying the split ratio kq and analysising the hydraulic characteristics of AHFB with different kB, βs and Fr, the formula between kq and parameters is obtained; The research result shows that:1) The kq increases with the increase of kB, but decrease with the increase of βs.2) The inlet Fr has a smaller effect on kq.(2)Studying the water tongue diffusion, in order to describe jet trajectory length of this bucket, water tongue diffusion width B and dimensionless parameter ξL are introduced. Dimensional analysis shows that:1) The kB has little effect on water tongue diffusion.2) The ξL decreases with the increase of kB and βs, the ξL and B increase with the increase of q and Fr.(3)The bottom and sidewall pressure of bucket are analyzed, the results show that the pressure distribution curve is unimodal type on upper bucket, but bimodal type on lower bucket. When the kB is smaller, the peak value of the lower bucket is influenced by the centrifugal pressure, otherwise it’s influenced by kB; The unit width discharge q is smaller, the action of water tide on the narrowing outlet makes the pressure distribution curve is bimodal type on lower bucket. When the water profile is higher than sidewall, the pressure distribution curve approaches unimodal type. The study on the sidewall shows that the cavitation number of AHFB is smaller than other ordinary flip bucket, cavitate erosion is less likely to occur in the sidewall.(4) Analyzing the pressure distribution and pressure pulse variances of the downstream bottom. As the unit width discharge increases, the pressure of downstream plunge pool become larger and the largest shock point is further. △Pm/(γL) is taken to reflect the comprehensive influencing factors of the plunging pressure, the pressure of the bottom is decreased with the decrease of △Pm/(γL). It is found that when 0.167≤κB≤0.458, the pressure distribution is better under the present conditions.(5) The BP neural network is introduced to forecast the optimal objective ψof AHFB, influenced by ξL、Ki and △Pm/(γL). The prediction results show that when the bucket width radio within 0.4～0.5, the target function ψ reaches its peak value. The selection of bucket shape and the optimal kB under different inflow q were obtained by BP neural network, which is significance in bucket shape optimization.