title: Collective Flow Enhancement by Tandem Flapping Wings.
abstract: We examine the fluid-mechanical interactions that occur between arrays of flapping wings when operating in close proximity at a moderate Reynolds number (Re≈100-1000). Pairs of flapping wings are oscillated sinusoidally at frequency f, amplitude θ_{M}, phase offset ϕ, and wing separation distance D^{*}, and outflow speed v^{*} is measured. At a fixed separation distance, v^{*} is sensitive to both f and ϕ, and we observe both constructive and destructive interference in airspeed. v^{*} is maximized at an optimum phase offset, ϕ_{max}, which varies with wing separation distance, D^{*}. We propose a model of collective flow interactions between flapping wings based on vortex advection, which reproduces our experimental data.
authors.affiliation: SEAS, Harvard University, Cambridge, Massachusetts 02138, USA.|OEB, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Nick
authors.initials: N
authors.lastname: Gravish
authors.affiliation: OEB, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Peters
authors.affiliation: NPB, University of California Davis, Davis, California 95616, USA.
authors.forename: Stacey A
authors.initials: SA
authors.lastname: Combes
authors.affiliation: SEAS, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wood