Effect of phase change on shock wave and n-dodecane droplet interaction with numerical investigation

TL;DR

This study uses high-resolution numerical simulations to analyze how phase change influences shock wave interactions with n-dodecane droplets, affecting deformation, fragmentation, and instability development.

Contribution

It provides a comparative analysis of shock-droplet interactions with and without phase change, highlighting the effects of phase change on droplet behavior under shock impact.

Findings

Phase change enhances Kelvin-Helmholtz instability waves on the windward surface.

Phase change inhibits KHI development on the leeward surface due to vaporization.

Higher Mach numbers suppress droplet flattening and vaporization, while enhancing shear stripping.

Abstract

In a real propulsion system, shock-droplet interaction is often accompanied by phase change, which has a significant effect on the deformation and fragmentation of the droplet. In this paper, we study the effect of phase change on the n-dodecane droplet propulsion, deformation and fragmentation impacted by shock waves with high-resolution numerical simulations. First, we conduct a comparative study on shock waves and n-dodecane droplets interaction with and without phase change model. The impact of the shock wave changes the pressure and temperature distribution around the droplet, causing the droplet liquefaction on the windward side. With the influence of phase change, the Kelvin-Helmholtz instability (KHI) waves on the windward surface are enhanced, the development of KHI waves on the leeward surface of droplet is inhibited by vaporization. Furthermore, it is found that phase change suppresses both the flattening of the cylinder and shearing of the sheet at droplet equator. Next, we investigate the effect of Mach number on shock-droplet interaction with consideration of phase change. As the shock Mach number increases, the flattening and vaporization of droplets are suppressed, the KHI waves on the windward surface and the shear stripping of the sheet at the droplet equator are enhanced. The shear stripping of the liquid sheet plays a more dominant role in the deformation and breakup process than the flattening of the droplet under the SIE breakup mechanism in a higher Mach number.