On the quantification of preferential accumulation

It is well-known that heavy particles in homogeneous isotropic turbulence tend to collect in certain regions of the flow, leading to preferential accumulation. In this study, we investigate different measures of preferential accumulation, some of which show a dependence on Reynolds number. All the measures used in this study confirm that this phenomenon is most pronounced for a Stokes number, St ∼ 1, based on the Kolmogorov time-scale. The variation with Stokes number has been studied over a wider range for all the measures than in previous studies. Though the effect of changing St, for a particular Re, has been well understood, the scaling with Re is not so obvious. The measures used in this study seem to suggest a structure to the particle concentration field which scales with Re. To investigate this structure, we introduce a concentration distribution length scale which shows a dependence on Re, especially at higher St. The results in the present work agree with several previous computational and experimental works and provide a more unified picture of the dependence of preferential accumulation on St and Re.