Experimental study of vortex dynamics in eccentric collision of vortex rings

Abstract This study investigates eccentrically colliding vortex rings using Particle Image Velocimetry (PIV) measurements. Under a fixed Reynolds number, we explore how eccentricity influences flow characteristics and behavior. Diverse collision dynamics at various eccentricities are revealed by analyzing flow structures from Lagrangian and Eulerian frames. When the eccentricity H/Rring = 0, frontal collisions cause significant deformation and breakup due to induced radial flow between oppositely rotating vortices. Increasing eccentricity (H/Rring = 0.893) leads to similar dynamics with noticeable trajectory deviations. At H/Rring = 1.786, momentum exchange altered the trajectory of the vortex rings and led to material exchange between them. The opposing flow induced by the neighboring vortex ring increases the vortex strength, and the vortex ring is eventually stretched and broken apart gradually. Further increasing to H/Rring = 2.679, the vortex cores merged, underwent subsequent splitting, 1 and involved material exchange. They eventually returned to their initial state. The vortex strength experiences an initial increase, followed by a decrease, and then a recovery. At the highest eccentricity (H/Rring = 3.572) and beyond, there is no interaction between the vortex rings. This study provides insights into vortex dynamics during eccentric collisions, highlighting eccentricity’s role in shaping flow dynamics.