A computational study of the role of particle size standard deviation on the collision frequency in differential settling

作     者：C.HEILIGER N.B.KAYE F.Y.TESTIK 

作者机构：Civil EngineeringClemson UniversityClemsonSC29634USA 

出 版 物：《International Journal of Sediment Research》 (国际泥沙研究(英文版))

年 卷 期：2013年第28卷第1期

页      面：34-45页

核心收录：

学科分类：0709[理学-地质学] 0819[工学-矿业工程] 08[工学] 0708[理学-地球物理学] 0818[工学-地质资源与地质工程] 081501[工学-水文学及水资源] 0903[农学-农业资源与环境] 0815[工学-水利工程] 0816[工学-测绘科学与技术] 

基　　金：the support of the Clemson University Department of Civil Engineering for their support of this research through a graduate teaching assistantship 

主　　题：Settling Sediment size distribution Sediment collision frequency Coefficient of variation 

摘      要：The results of a simple computational model for differential settling are presented illustrating the significant role that particle size distribution plays in collision frequency and sedimentation rate of particles in a quiescent environment. The model tracks a large number of particles（order 10;） with log-normally distributed diameters,as they settle at their Stokes settling *** collisions are detected and result in larger particles that fall more rapidly.A number of simplifying assumptions are made in the model in order to avoid empirical correlations for phenomena such as collision efficiency and particle *** simplifying assumptions were needed to isolate and quantify the role of the particle size *** concentration profiles indicate that,even in the absence of collisions, the standard deviation（σ;） of the particle size strongly influences the bulk mass settling rate as,for largerσ;, more mass is concentrated in larger,faster falling *** collision frequency is also a strong function ofσ;. For a given mass concentration the collision frequency first increases linearly with increasingσ;as greater variation in particle size leads to greater variation in particle velocity,and shorter times for particles to catch each *** largerσ;more mass is concentrated in larger particles,so,for a given mass concentration,there are fewer particles per unit volume,increasing the mean distance between the particles and reducing the collision *** implications of these results for sedimentation measurement using optical attenuation techniques are discussed.