孔-堰结合型鱼道过流元件的水动力特性及应用研究

Hydro-dynamical Properties of Orifice-weir in a Fishway and Its Application

为了解决鱼道水位落差大、流速高、难以平顺过渡问题,提出一种新型的孔-堰结合过流元件;试图通过这种新结构调控上下分流比,获得适宜鱼类洄游的水流条件.采用理论分析、数值模拟与水力模拟试验的综合研究方法,开展了一般性分析与典型鱼道研究.首先对孔-堰的特性及水力计算进行分析,给出适宜的分流模数与设计方法.以某鱼道过渡段为研究对象,对常规多级堰与多级孔-堰的水力特性开展数值模拟和模型试验研究,获得不同边界的流场水力要素.研究表明,具有上下通道的孔-堰呈双峰型流速垂线分布,比无孔-堰的偏态单峰分布更适合不同流层鱼类上溯;多级孔-堰调整了水流结构,使各级潜堰上下游水头差降低30%~50%;堰顶流速降幅达23%~40%,为1.2~2.1m/s,底孔流速保持在0.8~1.3m/s;孔-堰分流比沿程呈逐级增大(13%~39%)特征.孔-堰过流元件使流场整体紊动性减弱,堰顶湍动能降低58.8%~76.9%;底部加糙使能耗结构趋于合理,有益于鱼类上溯与休憩;同时保持平缓、连续的自由水面,具有良好的水力生态调节作用.

In order to solve the problem such as large water level drop,high velocity and non-smooth transition,a new way combining orifice and weir(O-W)is put forward on the basis of traditional design.By regulating the ratio of flow diversion,the suitable velocity distribution for fish migration is obtained,thus enriching the hydraulic design theory of fishway elements.The general analysis and typical fishway research are carried out by using the comprehensive research methods of theoretical analysis,numerical simulation and hydraulic model test.Firstly,the characteristics and hydraulic theory of the O-W elements are analyzed.Then suitable flow diversion modulus and design method are given preliminary.Taking the transition section of a proposed fishway as the typical object,the hydraulic ecological characteristics of multistage conventional weirs and multistage orifice-weirs are studied by means of hydrodynamic numerical simulation and physical model.The hydraulic factors in the flow field such as water level,velocity and turbulent kinetic energy with different boundary have been obtained.The results show that the bimodal velocity profile in orifice-weir can well meet the requirements for different layers migration than a single peak skewness distribution in the pure weir.By optimal multistage orifice-weir scheme,flow construction can be adjusted,which reduce the water drop between the upstream and downstream of the weir by 30%~50%,decreased down the velocity over weir to 23%~40%(at 1.2~2.1 m/s),and kept the velocity path the orifice at 0.8~1.3 m/s.Along the path of fishway,the diversion ratio of orifice-weir increases step by step(13%~39%).The orifice-weir elements can reduce the turbulence,reduce the turbulent kinetic energy 58.8%~76.9%in weir top and make the energy dissipation structure more reasonable by roughing bottom.It is beneficial to fish to trace back and rest,and to maintain a smooth and continuous free surface,which has good hydraulic ecological regulation.