| The Flaring pier+stepped spillway+stilling basin is widely used in the form of the joint energy dissipation,so that the large drainage condition in the high water head and big unit width flux,the phenomenon such as insufficient negative pressure and aeration is appeared in the partial steps on the face of the stepped spillway,the final show the cavitation erosion problem be discovered in the stepped surface,the combination of different size transitional stepped and aerator use can increase the aerated water and is conducive to abate stepped cavitation below.This paper on the"Study on the influence of connection mode between laddered surface and WES surface on hydraulic characteristics of the joint energy dissipation of flaring pier+stepped spillway+stilling basin?51569010?"the national natural science foundation of China,by means of hydraulic model,combined with Ahai hydropower station of 1:60 scale based on physical experiment,The influence of the combined action of different sizes of transition steps and aerators on the hydraulic characteristics is studied,which provides a certain degree of experimental basis for the development of the combined energy dissipator of flaring pier+stepped spillway+stilling basin.The main research results of this parer are as follows:?1?The comparison between the 14 groups of schemes shows that there is a positive correlation between the length of the aerated cavity and the size of the transition step,and the variation rule of the aerated concentration is consistent with the length of the aerated cavity.As the size of the transition step increases,the length of the maximum aerated cavity is 16.25m,and the maximum aerated concentration is 42%,both of which appear in scheme Ca.Therefore,the combined use of aerators and transition steps can effectively avoid cavitation damage on the step surface.Namely aeration characteristics of the optimal scheme for the aerators angle is 11.3°,transition step is three group of 2m×1.5m?high×width?combinations.?2?Through the analysis of 14 groups of schemes,it can be seen that the maximum negative pressure of the transition step surface appears at the no.1measuring point of a vertical face,and the negative pressure of the no.1measuring point of scheme Ca is the minimum,which is-0.17kpa.Therefore,adding aerators and increasing the size of the transition step and the angle of the aerator are beneficial to reducing the negative pressure of the transition step surface.So transitional step surface pressure minimum scheme for the aerators angle is 11.3°,transition step is three group of 2m×1.5m?high×width?combinations.?3?The analysis of 14 set of scheme,the biggest time-averaged pressure in pile number 0+092.00m,and the scheme of Ca in the pile when the number of the time-averaged pressure of the minimum of 417.51 kpa,therefore,as the size of the transition steps and aerator angle increases,which can reduce the segment and the stilling basin base plate when the time-averaged pressure,for the segment of each pile number in the base plate and subsequent security and stability.Therefore,the time-averaged pressure of the smallest scheme for the aerators angle is 11.3°,transition step is three group of 2m×1.5m?high×width?combinations.?4?The maximum depth of the basin is 47.19m,and the bottom-reaching velocity in the basin is 16.13m·s-1,which appears in scheme Ca.Therefore,the larger the angle of aerator and the size of transition step,the greater the water depth of the stilling basin,and the smaller the bottom-reaching velocity,which is more conducive to the mixing of the downstream flow in the stilling basin,and the energy dissipation effect is more better.Accordingly,the maximum stilling basin water depth and the minimum velocity in the scheme for the aerators angle is 11.3°,transition step is three group of 2m×1.5m?high×width?combinations.?5?The energy dissipation rate of scheme Ca is the best among the 14 groups of schemes,and its value is 66.71%.It can be seen that the effect of energy dissipation can be improved by adding aerator.The larger the angle of aerator and the size of transition step,the higher the energy dissipation rate.Therefore,the aerators angle is 11.3°,transition step is three group of 2m×1.5 m?high×width?combined form of 14 groups of relatively optimal solution.The size of the transition step and aerator is appropriately increased,and the hydraulic characteristics and energy dissipation rate of the combined energy dissipator are relatively better in all aspects,which is favorable for the combined energy dissipation form.Therefore,the scheme Ca is the best scheme in the 14groups of experiment scheme,namely the selection of the aerators angle is 11.3°,transition step is three group of 2m×1.5 m?high×width?combined form as the best experiment scheme. |
PDF Full Text Request