Abstract

A peeling bubble of air propagates when a newborn breathes for the first time. In experimental conditions, peeling fingers are unstable depending on the cross-sectional area and capillary thresholds. In this work, the deformation of a thin elastic membrane on top of a channel and its interaction with the boundary layer/solid plate yields interface wavenumbers in agreement with K41 theory defining inertial, turbulent, and dissipative regimes. Three-dimensional solutions of the minimal set of equations at the low stiffness and low capillary ranges yield symmetric round-type bubbles in numerical simulations. The mechanism responsible for the increase/decrease in the air bubble speed at large time scales is related to the wetting ridge gradient developed around the finger that defines two sorts of propagation: (i) the speed of the bubble decreases transferring energy to the membrane-fluid interface and (ii) the air finger increases its speed as it obtains energy from the elastic membrane and fluid layer, decreasing their temperature. The menisci at the bubble-liquid-shell interface are triggered by elastic and capillary forces that deform the interface around the finger, and the scale of these ridges is of the order of the elastocapillary length.