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Aerospace 2019, 6(2), 21; https://doi.org/10.3390/aerospace6020021

The Replication Hypothesis along the Take-Off Run and a System of Equilibrium Equations at the Lift-Off of a Protobird

School of Arts and Sciences, Embry-Riddle Aeronautical University, San Diego, CA 92123, USA
Received: 3 November 2018 / Revised: 3 January 2019 / Accepted: 2 February 2019 / Published: 15 February 2019
(This article belongs to the Special Issue Bio-Inspired Aerospace System)
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Abstract

An extant bird resorts to flapping and running along its take-off run to generate lift and thrust in order to reach the minimum required wing velocity speed required for lift-off. This paper introduces the replication hypothesis that posits that the variation of lift relative to the thrust generated by the flapping wings of an extant bird, along its take-off run, replicates the variation of lift relative to the thrust by the flapping wings of a protobird as it evolves towards sustained flight. The replication hypothesis combines experimental data from extant birds with evidence from the paleontological record of protobirds to come up with a physics-based model of its evolution towards sustained flight while scaling down the time span from millions of years to a few seconds. A second hypothesis states that the vertical and horizontal forces acting on a protobird when it first encounters lift-off are in equilibrium as the protobird exerts its maximum available power for flapping, equaling its lift with its weight, and its thrust with its drag. View Full-Text
Keywords: aerodynamics; protobird; replication hypothesis; equilibrium equations; normalized lift; normalized thrust; normalized drag; evolution; sustained flight; flapping; Strouhal number; take-off run; lift-off aerodynamics; protobird; replication hypothesis; equilibrium equations; normalized lift; normalized thrust; normalized drag; evolution; sustained flight; flapping; Strouhal number; take-off run; lift-off
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Burgers, P. The Replication Hypothesis along the Take-Off Run and a System of Equilibrium Equations at the Lift-Off of a Protobird. Aerospace 2019, 6, 21.

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