Oscillation behavior of liquid-in-liquid compound drops in a surrounding liquid under an impact

In this study, we conduct a systematic numerical investigation of the underlying mechanism of the oscillation behavior of liquid-in-liquid compound drops in a surrounding liquid under an impact. Based on the good agreement of the dimensionless scales of the pure drops during the oscillation behavior with experimental data, and employing energy budget analysis, we systematically investigate the influence of the volume ratio α, the Weber number We, the viscosity ratio η, the density ratio ε, and the interfacial tension ratio λ on the oscillation behavior of liquid-in-liquid compound drops. Two shape parameters, eouter and einner, are selected to describe the oscillation behavior of the compound drops. The influence of the above dimensionless parameters on the oscillation amplitude and period of the outer droplet (eouter) and inner droplet (einner) is studied. The influence of the above dimensionless parameters on the motion of the inner droplets of the oscillating compound drops is also investigated. Additionally, we theoretically propose a scaling law relating the maximum deformation of the compound drops to the dimensionless parameters, which is validated with the numerical results and experimental data.