Acceleration of tracer and light particles in compressible homogeneous isotropic turbulence

TL;DR

This study investigates how tracer and light particles accelerate in compressible isotropic turbulence using DNS data up to Mach 1, revealing distinct acceleration behaviors linked to flow structures near shocklets.

Contribution

It provides new insights into particle acceleration statistics in compressible turbulence, highlighting differences between tracer and light particles and their relation to flow features.

Findings

Flatness factor of acceleration increases with Mach number for tracers.

Light particles show a maximum in acceleration flatness at Mach 0.6.

Acceleration skewness varies differently for tracers and light particles with Mach number.

Abstract

The accelerations of tracer and light particles in compressible homogeneous isotropic turbulence (CHIT) is investigated by using data from direct numerical simulations (DNS) up to turbulent Mach number $M_t =1$. For tracer particles, the flatness factor of acceleration components, $F_a$, increases gradually for $M_t \in [0.3, 1]$. On the contrary, $F_a$ for light particles develops a maximum around $M_t \sim 0.6$. The PDF 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, $S_a$, firstly 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 light particles appear also in the zero-crossing time of acceleration correlation. It is argued that all these phenomenons are intimately linked to the flow structures in compression regions, e.g. close to shocklets.