Figure 1.

Anatomical features of a jellyfish and the vortex arrangement over the course of a swim cycle for the moon jellyfish (Aurelia aurita). Red = stopping vortex, blue = starting vortex. Black arrows = direction of fluid circulation. (1) and (5) Passive energy recapture mechanism (Gemmell et al. [16]). (2) Utilization of suction thrust from the upstream stopping vortex (Colin et al. [25]; Gemmell et al. [22]). The significance of the early stages of vortex–vortex interactions at the subumbrellar surface has not been investigated and is the focus of the present study. (3) Completion of the bell contraction. The starting vortex travels downstream in the wake after cancellation of the stopping vortex (Dabiri et al. [17]). (4) The stopping vortex is enhanced and repositioned inside the subumbrellar cavity (Gemmell et al. [22]). The newly formed stopping vortex and the downstream starting vortex interact to form a laterally oriented vortex superstructure (Dabiri et al. 2005 [23]). (Online version in colour.)