Wake structure and thrust generation of a flapping foil in two-dimensional flow
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Date
2017-02-10
Publication Type
Journal Article
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yes
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Abstract
We present a combined numerical (particle vortex method) and experimental (soap film tunnel) study of a symmetric foil undergoing prescribed oscillations in a two-dimensional free stream. We explore pure pitching and pure heaving, and contrast these two generic types of kinematics. We compare measurements and simulations when the foil is forced with pitching oscillations, and we find a close correspondence between flow visualisations using thickness variations in the soap film and the numerically determined vortex structures. Numerically, we determine wake maps spanned by oscillation frequency and amplitude, and we find qualitatively similar maps for pitching and heaving. We determine the drag–thrust transition for both pitching and heaving numerically, and we discuss it in relation to changes in wake structure. For heaving with low oscillation frequency and high amplitude, we find that the drag–thrust transition occurs in a parameter region with wakes in which two vortex pairs are formed per oscillation period, in contrast to the common transition scenario in regions with inverted von Kármán wakes.
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published
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Journal / series
Volume
812
Pages / Article No.
Publisher
Cambridge University Press
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Subject
Propulsion; Vortex shedding; Wakes/jets
Organisational unit
03499 - Koumoutsakos, Petros (ehemalig) / Koumoutsakos, Petros (former)
Notes
It was possible to publish this article open access thanks to a Swiss National Licence with the publisher.