用PDF方程法分析悬沙垂线浓度分布  

ANALYSIS OF VERTICAL DISTRIBUTION OF SUSPENDED SEDIMENT USING THE PDF EQUATION METHOD

作　　者：傅旭东[1] 王光谦[1] 

机构地区：[1]清华大学水利系水沙科学教育部重点实验室,北京100084

出　　处：《力学学报》2003年第4期393-400,共8页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金委和水利部联合资助重大项目(59890200);清华大学骨干人才支持计划资助项目~~

摘　　要：从颗粒运动的PDF(概率密度分布函数)输运方程出发,建立颗粒相的质量、动量和脉动速度二阶矩方程。对于明渠二维恒定均匀流,利用垂向动量方程导出了新的泥沙扩散方程,表明颗粒脉动强度梯度、升力、重力沉降和紊动扩散都影响悬沙运动,说明了传统扩散方程的不足。理论分析了水沙两相物理属性和水流条件对泥沙扩散系数和浓度分布特征的影响,并通过细颗粒试验资料的分析进行了定量研究。Based on the PDF transport equation for particles in turbulent sediment-laden flows, the equations of mass, momentum and second moments for particulate phase were derived. A new theoretical model for particle concentration distribution was developed for two-dimensional, steady and uniform open-channel flows. The new model takes into account the effects of the lift force and the vertical gradient of particle velocity fluctuation, as well as the effects of sediment gravitational settling and turbulent diffusion which are successfully described by the traditional sediment diffusion theory. Comparison with experimental data shows that: (1) both the Schmidt number, β, and the sediment diffusion coefficient, εs, given in traditional theories increase with the diameter-to-depth ratio, particle Reynolds number, the density ratio of water-to-sediment, and the energy slope; (2) β decreases vertically from bottom to top for flows with fine sediments; and (3) the traditional diffusion equation may have large errors for flows with high values of β and ω0/u* and high concentration.

关 键 词：PDF方程 悬沙运动 挟沙水流 泥沙扩散方程 浓度分布 扩散系数 概率密度分布函数 恒定均匀流 明渠水力学 

分 类 号：TV142[水利工程—水力学及河流动力学] TV133.1