Two-phase Interactions between Propagating Shock Waves and Evaporating Water Droplets

TL;DR

This study uses numerical simulations to explore how shock waves interact with evaporating water droplets, revealing complex phenomena like droplet breakup, pressure oscillations, and spatial distribution changes in dilute two-phase flows.

Contribution

It introduces a hybrid Eulerian-Lagrangian simulation approach to analyze shock-droplet interactions, highlighting novel flow phenomena during droplet breakup.

Findings

Reflected pressure waves cause dispersed droplet distribution.

Oscillations in pressure, droplet size, and forces occur post-shock.

Droplet spatial distribution exhibits strong oscillations after breakup.

Abstract

One-dimensional numerical simulations based on hybrid Eulerian-Lagrangian method are performed to study the interactions between propagating shocks and dispersed evaporating water droplets. Two-way coupling for exchanges of mass, momentum, energy and vapour species is adopted for the dilute two-phase gas-droplet flows. Interphase interactions and droplet breakup dynamics are investigated with initial droplet diameters of 30, 50, 70 and 90 {\mu}m under an incident shock wave Mach number of 1.3. Novel two-phase flow phenomena are observed when droplet breakup occurs. First, droplets near the two-phase contact surface show obvious dispersed distribution because of the reflected pressure wave that propagates in the reverse direction of the leading shock. The reflected pressure wave grows stronger for larger droplets. Second, spatial oscillations of the gas phase pressure, droplet quantities (e.g., diameter and net force) and two-phase interactions (e.g., mass, momentum, and energy exchange), are observed in the post-shock region when droplet breakup occurs, which are caused by shock / droplet interactions. Third, the spatial distribution of droplets (i.e., number density, volume fraction) also shows strong oscillation in the post-shock region when droplet breakup occurs, which is caused by the oscillating force exerted on the droplets.