Acceleration statistics of tracer and light particles in compressible homogeneous isotropic turbulence

The accelerations of tracer and light particles (bubbles) in compressible homogeneous isotropic turbulence are investigated by using data from direct numerical simulations up to turbulent Mach number M-t = 1. For tracer particles, the flatness factor of acceleration components, F-a, increases gradually for M-t is an element of[0.3, 1]. On the contrary, F-a for bubbles develops a maximum around M-t similar to 0.6. The probability density function of longitudinal acceleration of tracers is increasingly skewed towards the negative value as M-t increases. By contrast, for light particles, the skewness factor of longitudinal acceleration, S-a, first becomes more negative with the increase of M-t, and then goes back to 0 when M-t is larger than 0.6. Similarly, differences among tracers and bubbles appear also in the zero-crossing time of acceleration correlation. It is argued that all these phenomena are intimately linked to the flow structures in the compression regions close to shocklets.