This study examines the dynamics of axis-offset collisions between two vortex rings using particle image velocimetry(PIV)measurements.At a fixed Reynolds number,the influence of axial separation on the flow evolution ...This study examines the dynamics of axis-offset collisions between two vortex rings using particle image velocimetry(PIV)measurements.At a fixed Reynolds number,the influence of axial separation on the flow evolution is systematically investigated.Finite-time Lyapunov exponent(FTLE)fields and combined vorticity-velocity analyses reveal three distinct interaction regimes.(1)In the collision and radial outflow regime(H/R_(ring)0.893,where H is the axial separation distance and R_(ring)is the ring radius),vortex rings undergo axial compression and generate strong radial outflows,with negligible material exchange between oppositely signed vortices.(2)In the collision and rebound regime(H/R_(ring)=1.786),the rings—bearing the same sign—experience a near-elastic rebound,leading to disintegration without reconnection.(3)In the merging-splitting and recovery regime(H/R_(ring)=2.679),the rings exhibit transient merging followed by splitting and coherence recovery,accompanied by significant material exchange.For even larger offsets(H/R_(ring)=3.572),interactions are negligible.These findings categorize axis-offset vortex ring interactions into three regimes based on flow behavior and yield insights relevant to enhanced mixing and heat dissipation in engineering applications.展开更多
基金supported by the NSFC Excellence Research Group Program on“Multiscale Problems in Nonlinear Mechanics”(Grant No.12588201)the National Natural Science Foundation of China(Grant Nos.12432011,12102246,12422208,12372219,12502258)。
文摘This study examines the dynamics of axis-offset collisions between two vortex rings using particle image velocimetry(PIV)measurements.At a fixed Reynolds number,the influence of axial separation on the flow evolution is systematically investigated.Finite-time Lyapunov exponent(FTLE)fields and combined vorticity-velocity analyses reveal three distinct interaction regimes.(1)In the collision and radial outflow regime(H/R_(ring)0.893,where H is the axial separation distance and R_(ring)is the ring radius),vortex rings undergo axial compression and generate strong radial outflows,with negligible material exchange between oppositely signed vortices.(2)In the collision and rebound regime(H/R_(ring)=1.786),the rings—bearing the same sign—experience a near-elastic rebound,leading to disintegration without reconnection.(3)In the merging-splitting and recovery regime(H/R_(ring)=2.679),the rings exhibit transient merging followed by splitting and coherence recovery,accompanied by significant material exchange.For even larger offsets(H/R_(ring)=3.572),interactions are negligible.These findings categorize axis-offset vortex ring interactions into three regimes based on flow behavior and yield insights relevant to enhanced mixing and heat dissipation in engineering applications.
