Optimal Study On Flood Discharging And Energy Dissipation Without Impact Of Jets In Air Of Dongzhuang Project

The remarkable characteristics of high arch dam flood discharging and energy dissipation is narrow valley, high water head, large discharge per unit width. The high speed flow and energy dissipation are very critical problem, so energy dissipation protection has become one of the key technical problems. The energy dissipation model of Ertan fully shows the advantages of impact of jets in air energy dissipation, but the biggest problem it caused is atomization which may threat the safety of the dam and downstream even damage them. Energy dissipation without impact of jets in air is a way to solve this problem.This paper did optimal study on flood discharging and energy dissipation without impact of jets in air through model test and numerical simulation based on Dongzhuang project. The details are as follows:(1) The flood discharge, the effect of energy without impact of jets, impact pressure of plunge pool and some other characteristics of 17 different kinds of optimization schemes of flaring gate piers on spillways was studied. Then summarized the influence law of different shape parameters act on hydraulic characteristics of surface spillway. The results showed that when the side wall extend outward, the maximum increase amplitude of water tongue longitudinal diffusion length is 21.5m,the water tongue shape stability improved, the largest decline of impact pressure is 73.9% compared with the conventional flaring gate piers scheme;(2)3 new kinds of surface spillway optimization are combined with different kinds of middle level outlets scheme, then did flood discharging and energy dissipation model experiment based on the combination. The flood discharge of surface spillway, effect of energy dissipation without impact of jets in air, impact pressure of plunge pool, fluctuating pressure were surveyed during the experiment. After comparison and analysis of hydraulic characteristics of different schemes, the results showed that the 3rd optimization scheme had the most extensive range of application, the most obvious water tongue gap and the best effect of energy dissipation without impact of jets in air. The decline of the largest impact pressure of plunge pool was 39.0% and18.1% respectively when compared with the 1st and 2nd scheme. The decline of the largest fluctuating pressure of plunge pool was 58.6% and 40.1% respectively when compared with the 1st and 2nd scheme. Finally, the 3rd optimization scheme was chosen as the best scheme.(3)The RNG k-? two-equational model for 3-D turbulent flow was applied to numerically simulate flood discharging and energy dissipation based on 3 kinds of optimization scheme, the result showed that the calculated result agree well with the test result.The simulation method was applied to study the impact pressure of plung pool on different kinds of level and location of the subsidiary dam, and decided the optimal subsidiary dam height is 34 m and the optimal location is 40 m forward.