Long time statistics of prolate spheroids dynamics in a turbulent channel flow

Abstract

Long time simulations of the dispersion of prolate spheroids in a turbulent channel are performed to study the effect of the averaging procedure on particle statistics. The turbulent flow at Reτ=180 is directly simulated (DNS) and 300000 ellipsoids, modelled as point-particles are tracked to produce statistics. After a long time, an initially uniform particle distribution reaches a steady state in which almost all particles are segregated in the viscous sublayer. The final state of the distribution depends on the particle shape and relaxation time. Statistics of the particle velocity (translational and angular), orientation and concentration are then computed, using different averaging durations, before and after the particle distribution reaches the equilibrium. The steadiness of the distribution may have a significant effect on the statistics, especially for those strongly tied to the particle wall-normal motion. A non negligible influence of the averaging duration is also noticed for some statistics of high inertia particles.