The flow induced by a jellyfish

Abstract

The purpose of this study is to understand the propulsion mechanism of a jellyfish during its swimming. We observed the motion of a jellyfish (Aurelia aurita) by a motion-capture camera, and measured the vector field of flow around a jellyfish by using a PIV (Particle Image Velocimetry) measurement. A jellyfish is considered to be principally propelled by a jet at the contracting phase of its motion. If that is true, it is interesting that a jellyfish never stops traveling even at the expanding phase. We found that a vortex ring with the opposite vorticity to shed vortex ring was inside a jellyfish body in the expanding phase. We discussed a cause of an increase in thrust force and keeping constant speed in the expanding phase.

Morphological Considerations of Fish Fin Shape on Thrust Generation

“…Both types of these fins were reported to contribute to vortex generation related to thrust. The thrust generated by aquatic organisms has been attributed to the production of a vortex ring using a digital particle image velocimetry (DPIV) technique (Ichikawa and Mochizuki 2008;Kikuchi and Mochizuki 2010;Sakakibara 2004).…”

Consideration of thrust in escaping motion of a mosquito larva

“…It is clear that the flow is a result of wriggling, but the thrust generation mechanism has not been clarified yet. A flow visualization around an aquatic animal was demonstrated by Stamhuis and Videler (1995) [7], Duren, et al (2002) [8], Leeuwen, et al (2007) [9] and Ichikawa and Mochizuki(2008) [10] for investigating kinematics of swimming motion. They investigated the induced flow patterns by swimming by using particle tracking velocimetry (PTV) and particle image velocimetry (PIV) methods.…”