Hydraulic Characteristics Of Dovetail+ Narrow Slit Energy Dissipator

The vast majority of large water conservancy projects use the spillway or flood discharging tunnel to discharge the unnecessary flood in reservoir,and energy dissipation method commonly use the ski jump energy dissipation.These projects often have characteristics of high head,large discharge and narrow channel,which deflecting flow can easily cause serious erosion of downstream river and even threaten the safety and stability of the project.After a lot of research and engineering practice,the slit-type energy dissipation breaks through the limit of conventional energy dissipater,lateral contraction force water flow overhangs,the vertical and longitudinal diffusion,and intensified turbulent air to improve the efficiency of energy dissipation and reduce downstream riverbed erosion.However,it is very easy to produce a strong phenomenon of flow-induced vibration in the slit type flip bucket,damaging the bucket structure.Due to the existence of the end notch,both sides of the flow in the dovetail-type flip bucket mainly jet from the middle of the gap to reach longitudinal and vertical diffusion effect,which can reduce the impact of high-speed water flow on the wall edge.However,it need to pick a large angle.Therefore,it is of great significance to study the characteristics of the combination of these two buckets to achieve complementary advantages.Because of the complexity of high velocity flow and the diversity of geological and geographical environment,in order to study the hydraulic characteristics of dovetail+narrow slit combined type flip bucket,this paper,on the basis of collecting and studying the domestic and foreign research results about the narrow slit bucket and the dovetail bucket,focused on Changheba Hydropower Station 2#flood discharging tunnel and analyzed the basic factors affecting the hydraulic characteristics of dovetail+ narrow slit energy dissipator with the method of physical model test and 3D numerical simulation.The main research content is as follows:(1)Conducting a more in-depth research on energy dissipation mechanism of dovetail+slit energy dissipator using the basic theory of slit type flip bucket,summarizing the main parameters which influence the flow of flip bucket and providing new thought for physical model test and numerical simulation.(2)A scale of 1:50 physical model of Changheba 2#flood discharging tunnel was established.Aimed at the different influence factors of the flow characteristics of the dovetail+ narrow slit energy dissipator,11 test schemes were designed.The parameters such as flow pattern,water depth and velocity distribution were analyzed.According to the test results,the energy dissipation and erosion test of the relatively optimal test scheme was carried out,and the optimal scheme was obtained from various comparison.(3)The three-dimensional numerical calculations off our different types of dovetail+narrow slit energy dissipator schemes in model tests were carried out by using the RNG turbulence model and VOF multiphase flow model in FLUENT.The flow pattern,velocity distribution,water line and dynamic water pressure distribution of different schemes were compared and analyzed.The results of numerical calculation were analyzed and in contrast with the results of model test to validate the scientific and accuracy of numerical calculation.The physical model test and numerical simulation are combined to supplement each other,which can provide reference for the study of hydraulic characteristics of the dovetail +slit combined type flip bucket.