燕尾形新式窄缝水舌挑坎水力特性研究

From the early research and tests, a new type flip bucket is put forward innovatively for the design of discharge structures. this kind of flip bucket can make the flow form typical narrow nappe after the outlet of discharge structures, while the flow is contracted at lateral direction and extruded at longitudinal direction and the pressure on sidewalls of discharge structure does not increased prominently. The dynamic and kinematics equations about the flow with the flip bucket will be built using theoretical mechaincs and hydromechanics methods. The vector velocity, formation mechanism of narrow nappe and hydrodynamic pressure on the sidewalls will be analysed. The reason that the pressure on sidewalls of this kind of flip bucket is much smaller than that of conventional narrow flip bucket will be analysed theoretically. The characteristics of jumping nappe of the flip bucket will be studied through a series of model experiments, and the relationships between the characteristics of nappe and the flow conditions, the parameters of flip bucket, the drop of nappe will be generalized. A series of calculation method of trajectory length, extension length and inflow angle of the flip bucket will be built, and this may provide theoretical foundation for the design of hydraulic engineering project.

通过研究，创新性地提出一种燕尾形新式窄缝水舌挑坎，它能使水流在挑坎出口后横向收缩、纵向拉伸，从而形成典型的窄缝水舌形态，但挑坎侧墙所承受的压力却不明显增加；本研究拟采用理论分析结合数值模拟的方法，分析研究挑坎内水流运动过程中的流速及其方向随挑坎体型的变化情况，研究水流流经挑坎后形成窄缝水舌的机理，从理论上解释为何燕尾挑坎能形成窄缝水舌而侧墙受力却远远小于窄缝挑坎；通过系列模型试验，对燕尾形新式窄缝水舌挑坎的水舌特性、运动规律及其进入下游水垫后的消能特性进行分析研究，总结出挑坎的水舌特性随来流条件、挑坎体型参数及水舌落差变化的规律，建立一套燕尾形新式窄缝水舌挑坎的挑距、入水范围(拉伸长度)及入水角的计算方法，为挑流消能出口体型提供一种全新的模式，并为工程设计中采用燕尾形新式窄缝水舌挑坎提供可靠的理论依据。

通过理论分析计算和系列模型试验，对燕尾挑坎内的水流受力进行分析，研究表明燕尾挑坎是利用挑坎中部的前窄后宽的梯形缺口使一部分水流从缺口前端挑出，缺口两侧底板上水流则继续前进，并不断向挑坎中部的临空面挑出，最后少部分水流从末端挑出，这样使水流在自然重力作用下沿挑坎中轴线聚集并成纵向片状出挑，和空气充分掺气而消耗能量，进而形成窄缝水舌的力学机理，总结出燕尾挑坎的水舌参数随来流条件、挑坎体型参数及水舌落差变化的规律，建立一套燕尾挑坎水舌挑距、入水范围及入水角的计算方法，研究燕尾挑坎水舌的消能特性，提出了燕尾挑坎体型设计过程中反弧半径、前后端开口宽度、前后端挑射角度等关键体型参数的设计原则，为挑流消能出口体型提供一种全新的模式，并为工程设计中采用燕尾挑坎提供可靠的理论依据。