天然河道紊动扩散系数研究

Study on Turbulent Diffusion Coefficient in Natural River

在天然河流的水流泥沙数值模拟计算中,衡量模型模拟计算好坏的常用标准是模型的计算精度,而影响模型计算精度的因素主要体现在动量传递系数和紊动扩散系数的合理取值。在普朗特掺长假定和动量传递理论的基础上,将雷诺应力与时均流速梯度联系起来,并利用长江干流黄陵庙水文观测断面不同流量级、不同垂线脉动流速以及悬移质含沙量沿垂线分布的观测资料,计算与分析了水流的动量传递系数与小尺度紊动扩散系数的大小及其两者的关系,结果可为平面二维工程紊流计算问题提供参考依据。

In the numerical simulation of fluid flow and sedimentation in a natural river, the simulation precision is often referred to as a standard to judge the quality of a model. The factors that affect the model＇s simulation precision are represented by rational assignment of momentum transfer coefficient and turbulent diffusion coefficient. On the basis of Prandtl＇s mixing length and the momentum transfer theory, the Reynolds stress and time averaged velocity gradient are combined. Utilizing the field measured data obtained under the conditions of different discharges, vertical fluctuating velocities and the distribution of suspended sediment concentration along vertical lines at the Huanglingmiao hydrologic observation cross section on Yangtze River, the momentum transfer coefficient and small-scale turbulent diffusion coefficient are calculated and their relationships analyzed.