The Leading-Edge Vortex of Swift Wings

Abstract

A dual leading-edge vortex is recorded on a swift shaped wing, suggesting that the common swift exploits this flow feature while gliding. AbstractRecent investigations on the aerodynamics of natural fliers have illuminated the significance of the Leading-Edge Vortex (LEV) for lift generation in a variety of flight conditions. A well documented example of an LEV is that generated by aircraft with highly swept, delta shaped wings. While the wing aerodynamics of a manoeuvring aircraft, a bird gliding and a bird in flapping flight vary significantly, it is believed that this existing knowledge will serve to add understanding to the complex aerodynamics of natural fliers. In this investigation, the wing of a common swift Apus apus is simplified to a model with swept wings and a sharp leading-edge, making it readily comparable to a model delta shaped wing of the same leading-edge geometry. Particle image velocimetry provides an understanding of the effect of the tapering swift wing on LEV development and stability, compared with the delta wing model. For the first time a dual LEV is recorded on a swift shaped wing, where it is found across all tested conditions. It is shown that the spanwise location of LEV breakdown is governed by the local chord rather than Reynolds number or angle of attack. These findings suggest that the common swift is able to generate a dual LEV while gliding, potentially delaying vortex breakdown by exploiting other features non explored here, such as wing twist and flexibility. It is further suggested that the vortex system could be used 1 . CC-BY 4.0 International license not peer-reviewed) is the author/funder. It is made available under a

Kütle ve Kanat Alanı Grafiğinden Kanat Formlarının İncelenmesi

“…Since the effect of wing structure is more dominant in flapping wing flight, it is necessary to examine the arm-wings and hand-wings in detail. There are many studies on the flight style of swifts [26][27][28][29] however, there is no studies in the literature on the difference of swifts' hand-wings and arm-wings from the typical high-speed wings. In this study, based on the difference in wing structure, the wing form difference between scythe-shaped wing (SSW) and high-speed wings (HSW) was shown descriptively using photoshop, not quantitatively due to absence of experimental data.…”

Performance enhancement of downwind sails due to leading edge flapping: A wind tunnel investigation

“…Numerical simulations in Viola et al (2014) have also been performed on a fixed sail shape validated with wind tunnel experiments on flexible (Viola and Flay (2009, 2011) and semi-rigid sails (Bot et al (2013(Bot et al ( , 2014). Recent projects focused on the leading edge vortex flow pattern observed on downwind sail shape show promising results in the possible use of this phenomenon in other applications (Arredondo and Viola, 2016;Viola and Muir, 2017).…”