Evolution of the "First Bubble": Bubble and Jet Formation Within a Wine Bottle

When a liquid-filled bottle is inverted and allowed to empty, aside from the "glug" we hear, what do we see? What happens to the first bubble that rises into the neck? How does it form and evolve over time? We report on a set of experiments to address those questions, qualitatively and quantitatively, using a wine bottle. Due to the brief timespan of the first bubble evolution, a high-speed camera was needed to enable detailed observations of behavior. A MATLAB program was written to analyze these high-speed images and collect quantitative information. To explore the effects of liquid viscosity, we utilized a range of water-glycerin mixtures which yielded a wide range of Reynolds (10–20,000) and Weber (10–500) numbers, and limited range of Eötvös numbers (250-370). In our experiments we observed transitions in bubble characteristics (shape, size, motion, etc.) as liquid viscosity increased. After initial pinch-off within the bottleneck, bubbles in low viscosity liquids produced ejector jets which penetrated the top surface of the bubbles. Jet behavior varied with viscosity, exhibiting distinct changes in shape, pattern, and jet tip velocity. Supported by striking visuals, our findings provide deeper insight into the first bubble's formation and breakup as a function of viscosity.