Interaction of a thin vortex ring with a deforming and non-deforming bubble: Similarities and differences

In bubbly turbulent flows, the deformation of the bubble is known to play an important role in the interaction between the carrier phase and the dispersed phase. In order to understand the role of bubble’s deformability on these complex interactions, we experimentally study an idealization, namely, the interaction of a deforming air bubble (ρ_bubble/ρ_water ≈ 0.001) and a rigid buoyant particle (ρ_particle/ρ_water≈0.008, a rigid bubble), with a single water vortex ring (Re=6000–67300), with the main difference being the distinct difference in their deformability. The rigid and the deforming bubbles are directly engulfed into the vortex core. The deforming bubble undergoes elongation outside the ring during its capture, followed by elongation (azimuthally) and breakup inside the ring. In contrast, the rigid bubble remains spherical during capture, and stays more localized within the ring. We capture the deformability effects on the bubble dynamics and in modifications to the ring core's vorticity, the former measured using high speed imaging, and the latter with time-resolved PIV. The differences in deformability lead to distinct differences in the ring’s convection speed, azimuthal vorticity, and enstrophy. The details of these interactions, including both differences and similarities across the deforming and rigid bubble cases at low and large ring Reynolds numbers, will be presented at the conference.