Jellyfish-like robot for underwater surveillance

November 23, 2011 - via Virginia Tech

A biomimetic jellyfish surveillance robot // Source:

Researchers at the Department of Mechanical Engineering at Virginia Tech built an unmanned underwater vehicle (UUV) inspired by jellyfish morphology and propulsion mechanism. The UUV, dubbed Robojelly, was used to analyze the effects of the flexible margin on jellyfish propulsion.

The researchers say the natural animal has a bell section which deforms at a different phase then the rest of the bell. This lagging section, referred to as flexible margin or flap, is delimited by the bell margin and an inflexion point. The flap was replicated on the robotic vehicle by a flexible passive material to conduct a systematic parametric study.

In a preliminary experiment, Robojelly was tested without a flap and with a flap. This revealed a thrust increase over an order of magnitude. The researchers hypothesize that the length of this passive flap affects the vortex ring circulation strength of the jellyfish which can lead to higher efficiency and thrust. Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV) to analyze the change in vortex structures as a function of flap length. The robot input parameters stayed constant over the different configurations tested, thus maintaining a near constant power consumption.

The researchers say that the results clearly demonstrate that the flap plays an important role in the propulsion mechanism of Robojelly and provides an anatomical understanding of natural jellyfish.

— Read more in Alex Villanueva et al., “Effects of a fexible margin on Robojelly vortex structures” (paper presented at the 64th Annual Meeting of the APS Division of Fluid Dynamics, Baltimore, Md., 20-22 November 2011

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