Particle Image Velocimetry Measurement of Wall Shear Flow Around a Bubble Growing in Carbonated Water

An experimental technique was developed for two-dimensional Particle Image Velocimetry (PIV) measurement of wall shear flow around a bubble growing under dissolved gas supersaturation. Carbonated water was used as dissolved-gas-supersaturated liquid, and its flow was created in a small container with a tube pump. An isolated CO₂ bubble nucleated from an intentionally created scratch on the glass surface was placed in the flow. The mass-diffusion-driven growth of the bubble (from nucleation to detachment from the surface) was recorded using a video camera with backlighting; the radius of the detached bubble was below 1 mm in the present experimental conditions. The velocity field without and with the wall-attached bubble was obtained through PIV with the water (seeded with fluorescent particles) and with a planar laser sheet, which enables one to obtain local shear flow. With the measured liquid velocity at the bubble center, the particle Reynolds number was found to be below 1. The proposed PIV measurement technique allows for careful examination of bubble detachment dynamics and convective mass transfer around attached bubbles.