Two-phase flow measurements using PIV/PTV on an under expanded particle-laden jet

The objective of this study is to understand the dynamics of a high-speed particle-laden under-expanded jet motivated by landings on extraterrestrial bodies. In this setup, inertial particles are entrained and accelerated by an under-expanded jet. But, due to their inertia, the particle velocity is significantly lower than that of the surrounding gas, so the two phases are coupled through aerodynamic drag. Sub-micron oil droplets are entrained upstream before the inertial particles are introduced, whose velocity is determined through a PIV system; inertial particles, after image segmenting is performed to separate them from PIV data, are tracked over time using a PTV system. The results will help to understand particle-laden flow in a new regime where the background flow is compressible and the Mach number based on the slip velocity is not negligible, which may help to pave a foundation for future studies in compressible multiphase flows.