Collaborative Research: Hydrodynamic Instability and Breakup of Shock-driven Liquid Sheets

University Of North Carolina At Charlotte, Charlotte NC

Investigators

Abstract

When a strong shockwave passes through the interface between a solid and a gas, the solid can melt and form liquid sheets that are released into the gas. Typically, the solid surface will have roughness features that can cause ripples on the interface, leading to the formation of the liquid sheets. This phenomenon is called ejecta and occurs in several engineering applications and natural phenomena such as semiconductor manufacturing, nuclear fusion and weapons, ballistic projectile impact on an armored vehicle, asteroid impacts and supernovae explosions. Once the liquid sheets form, they can undergo further destabilization and break up into ligaments and eventually droplets. The process leading to breakup of the sheets is poorly understood and will be the focus of this study. The research will address this problem through detailed numerical simulations and detonation tube experiments. The findings from the simulations and experiments will be used to develop a ‘lifecycle’ model that can describe all stages of shock-driven liquid sheet evolution from initial formation, to growth, to fragmentation into ligaments and droplets. The project will support training of students in areas vital to national security. The overall goal of this project is to improve our understanding of the hydrodynamic instability mechanisms that govern the breakup of ejecta sheets in a gas, and the effect of such mechanisms on the size and velocity distributions of ejecta particles. Thus, the proposed work will help us understand the complex physics governing the breakup of ejecta into droplets. This is accomplished by investigating the problem at lower strain rates, so that every stage of the flow can be resolved by our detonation tube experiments and numerical simulations. Insights from the experiments and simulations will feed into the development of a ‘lifecycle’ model that will tie breakup dynamics to early-stage, linear instability physics. Having such an end-to-end model will enable control of liquid sheets in several industrial applications, by controlling the surface corrugations on the solid, so that a desired droplet distribution may be achieved. The breakup model developed will find broad usage as a sub grid model in simulations of impulsively driven sheets and jets. The project will help support the defense and security industries and will provide students the training to fill a vital workforce need in areas of national security. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.