窄缝消能工急流冲击波与水翅特性研究

The theory and technique of slit-type energy dissipator are widely used for the energy dissipation in hydropower stations, especially in those with high water head, narrow vally and large unit-width discharge.People have done much work on the energy dissipation mechanism and body design of this energy dissipator. Recently, it is found that the secondary water-wing produced in some spillway with slit-type dissipator may diffuse laterally and strike the bank slope , which will endanger the stability of the slope as well as the safety of the surrounding structures. Some preliminary study shows that the movement of the water-wing is obviously related to the upstream shock wave. Due to the no attention to the harmfulness of the water-wing, few achievements are obtained in earlier literature. .This project will focus on the shock wave and the water-wing in slit-type dissipator, and study the affect of the body parameters and inflow characteristic on the shock wave and the water-wing experimentlly and numerically. Then the formation mechanism and motion law of water-wing will be revealed,and the relationship between the shock wave and the water-wing will be established associating with the inflow and body parameters. Finally, the project will propose some principle and methods to effectively control the water-wing diffusion. .The results of this project will demonstrate the internal relationship between the jet shock wave and the water-wing motion in slit-type dissipator theoretically. It will also provide theoretical basis and technical support for the disaster prevention and risk avoiding of discharging constructions with slit-type energy dissipator.

收缩式窄缝消能工的理论和技术已被广泛运用于高水头、窄河谷、大单宽泄洪功率的水电工程实践中，其消能机理和体型设计已有较多研究成果。但部分采用窄缝消能设施的边孔泄槽泄洪时产生了水舌次生水翅横向扩散、冲击岸坡现象，对岸坡稳定及岸上建筑物安全构成危害。初步研究表明，水翅运动与水流冲击波密切相关。由于以往对窄缝水翅的危害认识不深，相关研究成果鲜见报道。本项目拟以冲击波和窄缝水翅为研究重点，采用水工模型试验和数值模拟计算方法，研究窄缝体型和来流特征参数对水流冲击波及水翅特性的影响；揭示窄缝水翅的形成机理和运动规律；构建与窄缝体型、来流条件相关联的水流冲击波与水翅扩散特性关系；提出能有效控制窄缝水翅扩散的设计原理和方法。该项研究将从理论上论证窄缝急流冲击波与水翅运动特性的内在关系，为采用窄缝消能设施的近岸泄槽防灾避险设计提供理论依据和技术支撑。

窄缝消能工水翅运动与收缩段急流冲击波密切相关，但以往对水翅的危害认识不深，相关研究成果鲜见报道。.本项目从2013年1月起历时4年，以窄缝急流冲击波和水翅为研究重点，采用理论分析、水工模型试验和数值模拟方法，在以往研究成果的基础上，对窄缝挑坎水力特性进行了系统分析；重点研究了窄缝挑坎挑角θ、收缩比β和收缩段起始断面水流弗氏数Fr对急流冲击波及水翅特性的影响；通过不对称边墙体型及加设贴角措施等研究了水翅控导措施。.1）系统研究分析了窄缝收缩段水面线、时均压力、流速流态、水舌等水力特性及随Fr、β及θ的变化规律；建立了无量纲化的窄缝收缩段底板最大时均压力及出口水深计算关系式。.2）对窄缝挑坎内急流冲击波进行了深入研究，用无量纲化的冲击波交汇点位置l和波后与波前水深比h’、冲击波波角φ等参数表征冲击波特性，建立了l与Fr及β的关系式；基于IPPEN冲击波理论提出了研究范围内的窄缝挑坎冲击波波角计算式。.3）系统测试了各试验工况下水翅空中形态及岸坡影响位置，分析推导出了估算水翅影响范围（LM、TM）的计算表达式。.4）首次提出并利用测试水翅降雨量方法来定量计算水翅对岸坡及建筑物的危害程度。提出用η表征水翅降雨形态系数、λ表征偏态系数、S表征降雨面积，M=ληS表征局地水翅危害强度。给出了各试验工况下，水翅扩散特性及M的分布规律，建立了窄缝急流冲击波与水翅扩散特性的内在关系。.5）探讨了在不影响下游消能防冲效果前提下，利用边墙不对称收缩或在收缩段侧墙底部加设小贴角体型来改变冲击波特性从而消减水翅侧向扩散措施，达到了预期效果，并在实际工程中得到了应用，效果良好。.该研究对于丰富窄缝消能工急流冲击波和水翅扩散理论以及拓展其水力设计成果具有重要的实际意义。