Particle Dispersion in Shear Turbulent Flows

Abstract

Applying the time series analysis idea to the spatial and temporal fluid-velocity correlation functions, a Lagrangian model for particle motion in anisotropic turbulent flows has been established. As applications, particle motion is numerically investigated in two shear turbulent flows: one flow is homogeneous and the other is not. In the present study, the Saffman lift force due to flow gradient is accounted for. Quantities such as the variations of particle dispersion tensor, the cross-correlation coefficient, and the principal angle of the particle dispersion tensor with time are calculated for 60 and 140-μm particles. As a reference, the corresponding quantities are also calculated for fluid dispersion. Comparisons for the cross-correlation coefficient and the principal angle of the fluid dispersion tensor are made with the available direct numerical simulation results. A good agreement is observed. For particle motion in the homogeneous flow, where the stochastic process of particle motion can be also regarded as homogeneous, the predicted asymptotic value of the cross-correlation coefficient of the particle dispersion, 0.84, adequately approaches the theoretical one, √3/2