On the relationship between turbulent motion and bimodal size distribution of suspended flocs

Abstract

The size distribution of suspended flocs is continuously changed by the flocculation process resulting from turbulent motion. This study aims to numerically investigate the effect of turbulent motion on the size distribution of suspended flocs. In this study, the methodology for modeling a floc size distribution is suggested by adopting the stochastic approach to modeling the flocculation process. The applicability of proposed methodology is examined by comparing numerical results with the field data measured in estuarine environments. It is known from the simulation results that the lognormal distribution can be used as a descriptor for unimodal size distribution of suspended flocs in the dynamic equilibrium state. The effect of turbulent motion on floc size distribution is further investigated by analyzing the floc size distributions at different elevations from bed. The bimodal size distribution of suspended flocs is replicated when the intensity of disaggregation and Kolmogorov length scale of turbulent eddy are considered. The disaggregation process of floc is mainly governed by the turbulent motion. Based on the relationship between disaggregation process and turbulent motion, it is insisted in this study that the shape of floc size distribution is significantly affected by turbulent motion.