ISSN:
1662-0356
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Natural Sciences in General
,
Technology
Notes:
Pulsed-jets are commonly used for aquatic propulsion, such as squid and jellyfishlocomotion. The sudden ejection of a jet with each pulse engenders the formation of a vortex ringthrough the roll-up of the jet shear layer. If the pulse is too long, the vortex ring will stop formingand the remainder of the pulse is ejected as a trailing jet. Recent results from mechanical pulsedjetshave demonstrated that vortex rings lead to thrust augmentation through the acceleration ofadditional ambient fluid. This benefit is most pronounced for short pulses without trailing jets.Simulating vehicle motion by introducing background co-flow surrounding the jet has shown thatvortex ring formation can be interrupted, but only if the co-flow is sufficiently fast. Recent in situmeasurements on squid have captured vortical flows similar to those observed in the laboratory,suggesting thrust augmentation may play a role in their swimming performance. Likewise, recentmeasurements with a mechanical self-propelled pulsed-jet vehicle (“robosquid”) have shown acruise-speed advantage obtained by pulsing
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/42/transtech_doi~10.4028%252Fwww.scientific.net%252FAST.58.237.pdf
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