Dynamics of floating two-dimensional bubbles rafts

Turbulent liquid jets impacting a liquid surface can entrain air and push bubbles underneath the liquid. The entrained air eventually rises to the free surface and may either form a collective "raft" of bubbles, or remain as isolated islands of bubbles. The stability and structure of these bubble rafts are determined by the turbulence and the surface tension of the air-water interface. Here we explore the statistical behavior of 2D bubbles rafts formed by an impinging jet, and the gravity-capillary waves emanating from the intermittent coalescence and bursting of the bubbles. We characterise the raft in terms of it's average radius, the radial distribution function, and the trajectories of the individual bubbles using particle tracking methods. We observe swarm-like collective dynamics for this passive particle-laden system, wherein cheerios-like capillary forces clump the bubbles together, while the turbulence and the background advective flow field pull the bubble raft apart. Simultaneously, we reconstruct the gravity-capillary waves generated on the free surface and the share insights into the audio spectrum.