Experimental study on the kinetic energy transfer mechanism of underwater vortex rings

The mechanism of vortex ring kinetic energy transfer is still unclear, which severely hinders the optimized design of underwater unmanned vehicles powered by vortex ring propulsion. The origin, evolution, and kinetic energy transfer of vortex rings are investigated through dye tracing, time-resolved particle image velocimetry, and coherent structure analysis techniques. The results reveal that the shape of the vortex ring plays a very important role in kinetic energy transfer. Vortex rings formed by circular and square orifices exhibit stable vorticity evolution and minimal dissipation, making them suitable for applications requiring consistent vortex behavior and energy propagation. In contrast, vortex rings from rectangular and elliptical orifices show greater instability, with axis-switching phenomena and increased vorticity dissipation, suggesting their potential use in applications where higher mixing efficiency and dynamic flow are needed. This study provides valuable insights into the role of orifice shape in determining the stability and performance of vortex rings, offering guidance for optimizing synthetic jets in various engineering applications such as fluid mixing and energy transmission.