Biofilm effects on size gradation,drag coefficient and settling velocity of sediment particles  

作　　者：Qian-qian SHANG Hong-wei FANG Hui-ming ZHAO Guo-jian HE Zheng-hui CUI 

机构地区：[1]Department of Hydraulic Engineering,State Key Laboratory of Hydroscience and Engineering,Tsinghua University [2]Nanjing Hydraulic Research Institute [3]China Institute of Water Resources and Hydropower Research

出　　处：《International Journal of Sediment Research》2014年第4期471-480,共10页国际泥沙研究（英文版）

基　　金：financed by the National Natural Science Foundation of China(51139003,11372161)

摘　　要：Sediment particles are often colonized by biofilm in a natural aquatic ecological system, especially in eutrophic water body. A series of laboratory experiments on particle size gradation, drag coefficient and settling velocity were conducted after natural sediment was colonized by biofilm for 5, 10, 15 and 20 days. Particle image acquisition, particle tracking techniques of Particle Image Velocimetry and Particle Tracking Velocimetry were utilized to analyze the changes of these properties. The experimental results indicate that the size gradation, the drag force exerted on bio-particles, and the settling velocity of bio-particles underwent significant change due to the growth of biofilm onto the sediment surface. The study proposes a characteristic particle size formula and a bio-particle settling velocity formula based on the regression of experiment results, that the settling velocity is only 50% to 60% as the single particle which has the same diameter and density. However, biofilm growth causes large particle which the settling velocities are approximately 10 times larger than that of primary particles. These results may be specifically used in the low energy reservoir or lake environment.Sediment particles are often colonized by biofilm in a natural aquatic ecological system, especially in eutrophic water body. A series of laboratory experiments on particle size gradation, drag coefficient and settling velocity were conducted after natural sediment was colonized by biofilm for 5, 10, 15 and 20 days. Particle image acquisition, particle tracking techniques of Particle Image Velocimetry and Particle Tracking Velocimetry were utilized to analyze the changes of these properties. The experimental results indicate that the size gradation, the drag force exerted on bio-particles, and the settling velocity of bio-particles underwent significant change due to the growth of biofilm onto the sediment surface. The study proposes a characteristic particle size formula and a bio-particle settling velocity formula based on the regression of experiment results, that the settling velocity is only 50% to 60% as the single particle which has the same diameter and density. However, biofilm growth causes large particle which the settling velocities are approximately 10 times larger than that of primary particles. These results may be specifically used in the low energy reservoir or lake environment.

关 键 词：Sediment particle BIOFILM Size gradation Drag coefficient Settling velocity 

分 类 号：TV142[水利工程—水力学及河流动力学]