A lattice Boltzmann model for the non-equilibrium flocculation of cohesive sediments in turbulent flow

Microflocs, which are the first-order aggregates of cohesive sediment, are formed during early-stage flocculation through random collisions in turbulent flow. This study proposes a numerical model to describe the non-equilibrium flocculation of cohesive sediments in homogeneous turbulent flows using the lattice Boltzmann method. The validity of the model is verified by analytical results. The influence of suspended sediment concentration and turbulence on the early-stage flocculation phenomena of cohesive sediments at the mesoscale is examined, and it is found that the number of microflocs increases with sediment concentration up to an optimum concentration of 2.0 kg/m(3), after which it decreases with sediment concentration. The mean settling velocities of the suspension sediments in the computational domain first increase with increasing shear rate, then decrease, and the optimum shear rate is approximately 17.6 s(-1). Additionally, the turbulence-induced flocculation process can have an influence on the turbulent flow. (C) 2013 Elsevier Ltd. All rights reserved.