  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 their aspect ratios. In particular, such particles are shown to
cluster more as their anisotropy increases. Further, the approach rate for
pairs of spheroids are 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.
