Publication: Flow interaction of three-dimensional self-propelled flexible plates in tandem
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2021-11-22
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Cambridge University Press
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Abstract
Tandem configurations of two self-propelled flexible flappers of finite span are explored
by means of numerical simulations. The same sinusoidal vertical motion is imposed on
the leading edge of both flappers, but with a phase shift (φ). In addition, a vertical offset,
H, is prescribed between the flappers. The configurations that emerge are characterized
in terms of their hydrodynamic performance and topology. The flappers reach a stable
configuration with a constant mean propulsive speed and a mean equilibrium horizontal
distance. Depending on H and φ, two different tandem configurations are observed,
namely compact and regular configurations. The performance of the upstream flapper
(i.e. the leader) is virtually equal to the performance of an isolated flapper, except in
the compact configuration, where the close interaction with the downstream flapper (i.e.
the follower) results in higher power requirements and propulsive speed than an isolated
flapper. Conversely, the follower’s performance is significantly affected by the wake of the
leader in both regular and compact configurations. The analysis of the flow shows that
the follower’s performance is influenced by the interaction with the vertical jet induced
by the vortex rings shed by the leader. This interaction can be beneficial or detrimental
for the follower’s performance, depending on the alignment of the jet velocity with
the follower’s vertical motion. Finally, a qualitative prediction of the performance of a
hypothetical follower is presented. The model is semi-empirical, and it uses the flow field
of an isolated flapper.
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Keywords
Swimming/flying, Flow-structure Interactions, Vortex interactions
Bibliographic citation
Arranz; G., Flores, O., García Villalba, M. (2022). Flow interaction of three-dimensional self-propelled flexible plates in tandem. Journal of Fluid Mechanics, 931, A5