Research On Hydraulic Characteristics And Influencing Factors Of Sudden Expansion And Sudden Aeration Facilities

The water resources is very rich in our country,with the rapid development of th e national hydropower facilities,more and more water releasing structures with high water head are designed and constructed.Thus,high-speed hydraulics problems attrac t more and more attention and the problem of aeration mitigation cavitation in high-sp eed flows are more and more important.The changes that air entraining facilities shape and inflow water head take to the high speed water hydraulic characteristics becomes very important.Although a lot of people have done some research on flow aeration and fluctuating pressure and have gotten some achievements,the developmen t of the theory on the mechanism relatively lags behind.In this paper,by the model tes t,authors study the sudden enlargement facility and the dip in shape aeration facility,by way that model test and theoretical analysis combine with each other,using the con trolling variable method.We conduct a serious research on drainage trough aeration c oncentration distribution and change rule,the distribution of time-average and pulsant pressure characteristic in the condition of different flow or depth of lip,and sudden ex pansion width.Through the analysis and discussion,we get the following results:(1)through controlling variable method,changing one of the three influence fact ors--the sudden expansion width,flow rate and depth of lip,comparing and analyzing the aerated concentration regularity in different water depths and different axis in the discharge.We get the regularity of aerated concentration that flows through the sudde n enlargement and dip type aeration facilities and how to obtain good aeration effect.(2)this paper introduces the method of data analyzing and processing of pulse pr essure,how to carry on the coefficient of variation,skewness coefficient,kurtosis coe fficient and the processing of spectrum characteristics of the fluctuating pressure data and the principle reflected by the data.(3)based on the data processing of pulse pressure,we get the rule of variation of total pressure pulsation in the discharge the largest pulsation is along the impact zone,along the present wave intensity is abating and finally stabilization.And time-average pressure presents a trend of decreased first then increased due to the characteristics of turbulent flow(4)using controlling variable method to analyze the regularity of fluctuation press ure in condition of different flow rate and different mixing gas drainage of fluctuating pressure in the tank,through the comparison and analysis of pulsation in the discharge pressure amplitude spectrum characteristics,probability density,etc.,it is concluded t hat the regularity of fluctuation pressure(5)comparing different aeration facilities in the sink under the pulsation pressure amplitude and the spectrum characteristic respectively,we find that the fluctuating pressure of aerated flow in different conditions fits in with the characteristics of low frequency and high amplitude at a high speed.