Role of bubble size on hollow droplet collision onto thin liquid film

The present work numerically explores the behavior of hollow droplet collision on a thin film surface by considering pertinent factors. Dimensionless quantities, such as diameter ratio (d/D), Weber number (We), Ohnesorge number (Oh), and film thickness Ho/D are employed to characterize the impingement mechanism of hollow droplets onto thin films. Characterization of radial spreading (f/D), edge jet (h/D), and central counter jet (L/D) is understood through a qualitative approach using numerical contours. Thus, temporal growth of f/D, h/D, and L/D are predicted for different values of We, d/D, and Ho/D. Similarly, predictions are extended for maximum spreading (fmax/D), maximum edge jet (hmax/D), and maximum central counter jet (Lmax/D) to enrich the characterization of insightful physics of hollow droplet collision on thin film surface. The reduction gradient of fmax/D with d/D is anticipated to be steeper at a higher We than a lower We. It is noticed that the gaseous bubble does not burst at a higher magnitude of Oh. Thus, a regime map on Oh−d/D plane is anticipated to distinguish two separate regimes, such as bursting and no-bursting zones. Fluidic behavior of impingement mechanism is elucidated using velocity vectors. Finally, we have also proposed relevant correlations to predict the maximum spread fmax*=fmax/D, maximum edge jet hmax*=hmax/D, and maximum central jet Lmax*=Lmax/D in terms of different pertinent input parameters.