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Whiskers reduce drag: harbor seals

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Harbor seal / Mike Baird / LicenseCC-by - Attribution

The highly sensitive whiskers of harbor seals reduce vortex-induced vibrations during swimming thanks to their undulated surface structure.

BIOMIMICRY TAXONOMY
Summary
"Harbor seals (Phoca vitulina) often live in dark and turbid waters, where their mystacial vibrissae, or whiskers, play an important role in orientation. Besides detecting and discriminating objects by direct touch, harbor seals use their whiskers to analyze water movements, for example those generated by prey fish or by conspecifics. Even the weak water movements left behind by objects that have passed by earlier can be sensed and followed accurately (hydrodynamic trail following). While scanning the water for these hydrodynamic signals at a swimming speed in the order of meters per second, the seal keeps its long and flexible whiskers in an abducted position, largely perpendicular to the swimming direction. Remarkably, the whiskers of harbor seals possess a specialized undulated surface structure, the function of which was, up to now, unknown. Here, we show that this structure effectively changes the vortex street behind the whiskers and reduces the vibrations that would otherwise be induced by the shedding of vortices from the whiskers (vortex-induced vibrations). Using force measurements, flow measurements and numerical simulations, we find that the dynamic forces on harbor seal whiskers are, by at least an order of magnitude, lower than those on sea lion (Zalophus californianus) whiskers, which do not share the undulated structure. The results are discussed in the light of pinniped sensory biology and potential biomimetic applications." (Hanke et al. 2010:2665)
About the inspiring organism
Med_1352607487_8802d654f5_b Harbor Seal
Phoca vitulina Linnaeus, 1758
Common name: Harbor seal

Learn more at EOL.org
Some organism data provided by: ITIS: The Integrated Taxonomic Information System
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist

Threat Categories LONG_LC IUCN Red List Status: Least Concern

Bioinspired products and application ideas

Application Ideas: Reducing drag on rod-like objects caused by vortex-shedding. Flow sensors for underwater vehicles or parts of buildings and offshore facilities with reduced vibrations from wind or water flow. Suppression of vortex-induced vibrations in flexible structures with low mass.

Industrial Sector(s) interested in this strategy: Aquatics, architecture, building, automotive

Experts
Marine Science Center
Prof. Dr. Guido Dehnhardt
University of Rostock
References
Hanke W; Witte M; Miersch L; Brede M; Oeffner J; Michael M; Hanke F; Leder A; Dehnhardt G. 2010. Harbor seal vibrissa morphology suppresses vortex-induced vibrations. Journal of Experimental Biology. 213: 2665-2672.
Learn More at Google Scholar Google Scholar  

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