Transitions in the wake of a flapping foil
Abstract
We study experimentally the vortex streets produced by a flapping foil in a hydrodynamic tunnel, using 2D Particle Image Velocimetry (PIV). An analysis in terms of a flapping frequency-amplitude phase space allows to identify: 1) the transition from the well-known B\'enard-von K\'arm\'an (BvK) wake to the reverse BvK vortex street that characterizes propulsive wakes, and 2) 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.
Keywords
Cite
@article{arxiv.physics/0702219,
title = {Transitions in the wake of a flapping foil},
author = {Ramiro Godoy-Diana and Jean-Luc Aider and José Eduardo Wesfreid},
journal= {arXiv preprint arXiv:physics/0702219},
year = {2011}
}
Comments
Revised version includes minor changes in the discussion of the drag coefficient calculation. The 4 figures are unchanged