The effect of large-scale turbulent structures on particle dispersion in wall-bounded flows

The effect of large-scale turbulent structures on the motion of heavy particles in wall-bounded turbulent flows is investigated by mining a direct numerical simulation database of particle-laden turbulent Couette flow, and comparing the results with a turbulent Poiseuille at similar friction Reynolds number. It is shown that the large-scale structures found in the core of the Couette flow have an influence on the turbophoretic mechanism, leading to different distributions of the particle concentration. The main differences in the two flows are observed in the spatial distribution of the suspended phase, which is found to be strongly dependent on the structure of the underlying streamwise velocity field. In addition to the standard particle streaks in the inner layer, spaced at 100 wall units, typical of the Poiseuille flow, in the Couette case particles with non-negligible inertia respond to the large-scale structures of the core, by organizing themselves into large-scale rows whose typical spanwise separation is of the order of 4-5 channel half-height. (c) 2012 Elsevier Ltd. All rights reserved.