Study On Optimization Of Aeration Facilities Of High Water Head In Spillway Tunnel

In recent years,the increasing number of high head discharge structures put forward higher requirements for aeration protection with the development of hydropower construction.Since the aerator directly determines the effect of aeration,therefore,study on the optimization of aeration facilities is significant meaning.This paper summarizes the results of previous studies,aiming at the optimization problem of gas mixing facility with high head discharge in a certain one spillway tunnel,by means of model test and numerical simulation,study on the hydraulic characteristics of the complex of the spillway tunnel sudden abrupt falling segment,The main research contents and results are as follows:(1)The results of the original design scheme of spillway tunnel test shows that:Sudden expansion and sudden drop of air mixing facilities in spillway tunne must be optimized,because of,when low water level it can not be formed a stable cavity,when high water level,the water wing is high,the flow pattern is poor;Two aeration facilities must be added in the lower reaches of the chute,for the reason of,the velocity of each section of the spillway is greater than 35m/s,and the maximum flow rate is 49.88m/s,the water flow cavitation number is relatively small,the minimum value is 0.07,more than,considering the effective protection range;(2)The body shape factors of sudden expansion and sudden drop have significant effects on the bottom cavity,the side cavity,the water wing and the downstream flow regime.Test and calculation results show that: The height of the bottom cavity and the length of the bottom cavity can be increased with the addition ofthe aeration facilities,the water wing height and length increased,the flow pattern becomes worse.The height of the bottom cavity and the length of the bottom cavity can be increased with increase downstream bottom slope,the water wing height and length increased,the flow pattern becomes worse.Adding the angle of the side wall,the side cavity becomes longer,the bottom cavity backwater is reduced,the water wing phenomenon is intensified,and the flow pattern becomes worse;(3)To keep the incident angle of water flow small,the flow pattern and bottom cavity backwater can be improved simultaneously.Compare the test results of different floor after thesudden expansion and fall get,when the incidence angle of the water flow is relatively small,the water tongue and the bottom plate can be connected smoothly,flow regime is easy to be stable,can make the back flow less,easy to form the cavity.In engineering practice,the bottom slope can be increased and the bottom plate can be raised to ensure that the incident angle of the water flow is small;(4)Pressure changes greatly when the water flows through the sudden expansion and sudden drop,On the side wall,the cavity area,the impact area,the pressure is relatively small and the stable area is formed,and the cavity area,the impact area and the stable area are formed on the bottom plate.The bottom of both sides of the wall corresponding to the impact point of the base plate is the maximum area of the side wall pressure.The calculated data show that the maximum pressure is close to two times the maximum pressure of the impact zone.Water pressure will change dramatically in a small range of impact area and small errors in the pressure measuring point will result in a large difference in the pressure value,so that,experiment may not be able to capture the maximum impact pressure,designer should pay attention to.