Pair dispersion of bubbles in turbulence

Pair dispersion is a classical tool to understand the mixing and transport of pollutants by turbulent flows. For light bubbles, the dispersion dynamics deviate from the tracer limit and provide a new way of understanding their coalescence and transport. One of the challenges for tracking a pair of bubbles with a very small initial separation experimentally is associated with triangulating bubbles and tracking them in a dense cloud. We approached the problem by leveraging our new bubble tracking method, which utilizes a novel feature correlation method combined with our open-sourced Shake-the-Box code. This method allows us to track pairs of bubbles very close to each other and enables us to obtain sufficient statistics to study bubble pair dispersion in homogeneous and isotropic turbulence. The results clearly show not only the ballistic and superdiffusive scaling but also a new transition scaling, which possibly implies the mutual trapping of the pairs in the turbulent vortices.