Hydrodynamic instability and breakup of a liquid-gas interface via vibration

Liquid-gas interfaces break up when subjected to large-amplitude oscillatory accelerations due to hydrodynamic instability. Interface breakup can lead to the injection of the gas phase into the liquid phase below. This gas injection can alter damping properties of fluid-structural systems and depends on the nature of early-stage interface breakup. The breakup that leads to gas injection depends on the configuration details, including the vibration frequency, acceleration amplitude, and character of the initial interface perturbation. We use a 6-equation Baer-Nunziato type diffuse interface model equipped with body force and surface tension effects to simulate early-stage interface breakup and the resulting injection of the gas into the liquid below it. The results indicate a reasonable agreement between simulation growth rates and linear stability analysis, as well as growth-rate independence across random interface perturbations at oscillating accelerations on the order of ten times Earth's gravity with frequencies in the hundreds of hertz. The formation of droplets due to the Rayleigh-Plateau instability in the jetting resulting from the violent acceleration is observed, as well as the entrainment of gas. The volume of ejected droplets and entrained gas are reported over time.