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Lift-induced drag

About: Lift-induced drag is a research topic. Over the lifetime, 2861 publications have been published within this topic receiving 41094 citations.


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Journal ArticleDOI
28 Feb 2014-PLOS ONE
TL;DR: This work hypothesised that, if a bird is limited in its ability to morph its wings and adapt its wing shape to suit both flight modes, then a preference towards flapping flight optimization will be expected since this is the most energetically demanding flight mode and tested this by studying a well-known flap-gliding species, the common swift.
Abstract: Many flying animals use both flapping and gliding flight as part of their routine behaviour. These two kinematic patterns impose conflicting requirements on wing design for aerodynamic efficiency and, in the absence of extreme morphing, wings cannot be optimised for both flight modes. In gliding flight, the wing experiences uniform incident flow and the optimal shape is a high aspect ratio wing with an elliptical planform. In flapping flight, on the other hand, the wing tip travels faster than the root, creating a spanwise velocity gradient. To compensate, the optimal wing shape should taper towards the tip (reducing the local chord) and/or twist from root to tip (reducing local angle of attack). We hypothesised that, if a bird is limited in its ability to morph its wings and adapt its wing shape to suit both flight modes, then a preference towards flapping flight optimization will be expected since this is the most energetically demanding flight mode. We tested this by studying a well-known flap-gliding species, the common swift, by measuring the wakes generated by two birds, one in gliding and one in flapping flight in a wind tunnel. We calculated span efficiency, the efficiency of lift production, and found that the flapping swift had consistently higher span efficiency than the gliding swift. This supports our hypothesis and suggests that even though swifts have been shown previously to increase their lift-to-drag ratio substantially when gliding, the wing morphology is tuned to be more aerodynamically efficient in generating lift during flapping. Since body drag can be assumed to be similar for both flapping and gliding, it follows that the higher total drag in flapping flight compared with gliding flight is primarily a consequence of an increase in wing profile drag due to the flapping motion, exceeding the reduction in induced drag.

47 citations

Journal ArticleDOI
TL;DR: In this article, an experimental investigation of rotor/wing aerodynamic interactions in hover is described, which consisted of both a large-scale and a small-scale test with a 0.658-scale V-22 rotor and wing.
Abstract: An experimental investigation of rotor/wing aerodynamic interactions in hover is described. The investigation consisted of both a large-scale and a small-scale test. A 0.658-scale V-22 rotor and wing was used in the large-scale test. Wing download, wing surface pressure, rotor performance, and rotor downwash data from the large-scale test are presented. A small-scale experiment was conducted to determine how changes in the rotor/wing geometry affected the aerodynamic interactions. These geometry variations included the distance between the rotor and wing, wing incidence angle, wing flap angle, rotor rotation direction, and configurations both with the rotor axis at the tip of the wing (tilt rotor configuration) and with the rotor axis at the center of the wing (compound helicopter configuration).

46 citations

Journal ArticleDOI
TL;DR: In this article, the experimental measurement and the numerical calculation of both the steady-state and the transient natural convective drag force around spheres at low Grashof numbers were performed in an electrodynamic balance for Grashoff numbers ranging from 0.002 to 0.03.

46 citations

Journal ArticleDOI
TL;DR: In this paper, a transversely oscillating cylinder in a uniform flow is modeled to investigate frequency effects of flow-induced wake on lift and drag of the cylinder, and the effects of frequency lock-in, superposition and demultiplication are discussed based on the spectral analysis of time histories of lift and drags.

46 citations

Journal ArticleDOI
TL;DR: In this article, a numerical analysis is performed to investigate the aerodynamic characteristics and static height stability of the endplate on an aspect-ratio-one wing in ground effect, which shows that the ground effect increases the lift by high pressure on the lower surface, reduces the induced drag, increases the suction on the upper surface, and consequently considerably enhances the lift-drag ratio.
Abstract: A numerical analysis is performed to investigate the aerodynamic characteristics and static height stability of the endplate on aspect-ratio-one wing in ground effect. The investigation is carried out on angles of attack from 0° to 10° and ground clearances at a trailing edge from 5% of chord to 50%. The analysis shows that the ground effect increases the lift by high pressure on the lower surface, reduces the induced drag, increases the suction on the upper surface, and consequently considerably enhances the lift-drag ratio. The endplate, which prevents the high-pressure air escaping from the air cushion and reduces the influence of wing-tip vortex, augments lift and lift-drag ratio further. Interestingly, the drag with the endplate does not increase as much as the lift does when the airfoil is brought close to the ground. From the analysis and visualization of computation results with the endplate, it is found that two wing-tip vortices are generated from each wing surface, their strengths are stronger, diminished rapidly and the influence of the wing-tip vortices are decreased. The outward drift of wing-tip vortex, which is generated from the lower wing surface, is observed. Irodov’s criteria are also numerically evaluated to investigate the static height stability of wings with and without the endplate. The comparison of Irodov’s criteria shows that the endplate is not favorable for static height stability but reduces the deviation of the static height stability with respect to pitch angles and heights.

46 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
2022105
202138
202046
201944
201849