Reynolds number effect on vortex ring colliding with a solid wall

Flow-visualization experiments have been conducted in a water tank to demonstrate the Reynolds number effect on a vortex ring colliding upon a flat plate with a trajectory of the vortex ring normal to the flat plate. These experiments take place in different Reynolds numbers (Re = 1000, Re = 3000, Re = 5000, and Re = 7000), which allows for both the laminar and turbulent states of a vortex ring at the same temperature. The planar laser-induced fluorescence technique is adapted to directly visualize the continuous changes of a vortex ring, and the particle image velocimetry technique is employed to initially measure the basic characteristics of the flow field. Upon Reynolds numbers, we observe the vivid variation of vortex ring motion ranging from laminar to turbulent. The flow-visualized results indicate that, as the Reynolds number increases, the dynamics and physics of the collision process have become increasingly complex, and the unstable properties of the vortex ring have been enhanced.