Instability of Two-Species Interfaces via Vibration

Vibrating liquid–gas interfaces can break up due to hydrodynamic instability, resulting in gas injection into the liquid below it. The bubble injection phenomena can alter fluid-structural properties of mechanical assemblies and modify fuel composition. The primary Bjerknes force describes the seemingly counter-intuitive phenomenon that follows: gas bubbles sinking against buoyancy forces. The interface breakup that initializes the injection phenomenon is poorly understood and, as we show, depends on multiple problem parameters, including vibration frequency. This work uses an augmented 6-equation diffuse interface model with body forces and surface tension to simulate the initial breakup process. We show that a liquid–gas interface can inject a lighter gas into a heavier liquid, and that this process depends on parameters like the vibration frequency, vibration magnitude, and initial perturbation wavelength.