Translational and rotational motions of inertial prolate particles in compressible turbulent channel flows

This study investigates the dynamics of spherical and prolate spheroidal particles in compressible turbulent channel flows using point-particle direct numerical simulations. We examine particles with a range of Stokes numbers and aspect ratios suspended in compressible turbulent channel flows with bulk Mach numbers from 0.3 to 3.0. Our results show that increased flow compressibility, which introduces non-uniform mean fluid density and viscosity, significantly alters particle spatial distribution, translational and rotational motion, and orientation. At higher Mach numbers, the particle Stokes number under semi-local viscous scaling decreases, leading to a weaker tendency for near-wall accumulation, preferential clustering, and reduced mean slip velocities. Furthermore, a higher bulk Mach number enhances the streamwise alignment of prolate particles at a fixed St+, increases the spinning rate of light particles, and suppresses the tumbling rate of heavy particles. These phenomena are amplified by intensified Lagrangian stretching and streamwise velocity fluctuations, combined with a shorter rotational response time about the particle's major axis. For more elongated particles, the observed increase in mean slip velocity is attributed to a greater probability of streamwise alignment, higher particle mass, and an enhanced spinning tendency.