Pair statistics of oblate spheroids settling in a turbulent flow

We perform direct numerical simulations of sub-Kolmogorov, inertial spheroids settling under gravity in homogeneous, isotropic turbulence, and find that small-scale clustering, measured via the correlation dimension, depends sensitively on the spheroid aspect ratio. In particular, such spheroids are shown to cluster more as their anisotropy increases. Further, the approach rate for pairs of spheroids is calculated and found to deviate significantly from the spherical-particle limit. Our study, spanning a range of Stokes numbers and aspect ratios, provides critical inputs for developing collision models to understand the dynamics of sedimenting, anisotropic particles in general, and ice crystals in clouds in particular.