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Updated: Jul 6, 2026

Flapping Soft Fin Deformation Modeling using Planar Laser-Induced Fluorescence Imaging
Published on: April 28, 2022
Transitions in the wake of a flapping foil
Ramiro Godoy-Diana1, Jean-Luc Aider, José Eduardo Wesfreid
1Physique et Mécanique des Milieux Hétérogènes (PMMH) UMR 7636 CNRS, ESPCI, Paris 6, Paris Cedex 5, France. ramiro@pmmh.espci.fr
Abstract:
We study experimentally the vortex streets produced by a flapping foil in a hydrodynamic tunnel, using two-dimensional particle image velocimetry. An analysis in terms of a flapping frequency-amplitude phase space allows the identification of (i) the transition from the well-known Bénard-von Kármán (BvK) wake to the reverse BvK vortex street that characterizes propulsive wakes, and (ii) the symmetry breaking of this reverse BvK pattern giving rise to an asymmetric wake. We also show that the transition from a BvK wake to a reverse BvK wake precedes the actual drag-thrust transition and we discuss the significance of the present results in the analysis of flapping systems in nature.
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