Effect of turbulent flow on flocculation of fine cohesive sediment
摘要
Using the fractal cluster growing model,the effect of turbulent flow on the flocculation velocity,the average diameter and the fractal dimension of flocs are studied.The model simulates the collision,the bonding and breakage of sediment particles under the action of Brown motion,gravity settling and turbulent flow in a three-dimensional space.The results show that the process of flocculation and average diameter of flocs can be divided into three stages: accelerating section,uniform section and descending section.The flocculation duration of uniform section appears to be first increasing then decreasing as the turbulent intensity increased,and so do the growth of average diameter.Moreover,the flocculation velocity and the flocs average diameter are smallest in the central region.The fractal dimension of flocs increases with the turbulent intensity increasing,and is finally stabilized.Besides,the fractal dimension of flocs appears to be first increasing then decreasing with time.The fractal dimension of floc is largest in the lower region,followed by the upper region,and the lowest value is found in the middle region.