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FLUKEPRINTS OF CETACEANS AND THE CORRESPONDING SHEAR FLOW PHENOMENON

Germain Rousseaux
Pprime Institute, UPR 3346, CNRS - Universite de Poitiers - ISAE ENSMA, 11 Boulevard Marie et Pierre Curie, Teieport 2, BP 30179, 86962 Futuroscope Cedex, France

David Uminsky
Department of Mathematics, University of San Francisco, 2130 Fulton Street, San Francisco, CA 94117-1080, USA

Rachel Levy
Harvey Mudd College 301 Platt Blvd, Claremont, CA 91711, USA

Résumé

When walking in the snow, mud or sand, our feet leave a characteristic imprint in the medium. The naturalists, hunters or paleontologists use them to identify animals. The medium have plastic properties which allow the persistence of the footprint. Here, we consider another kind of footprint, in a fluid medium, whose essential property is its ephemeral nature much like wake vortices after the take-off of an aircraft. We study the flukeprint of cetaceans at the surface of water. We will present laboratory experiments with an artificial fluke which show that the formation of flukeprints is mainly a wave-current interaction process with a peculiar shear flow.