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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
TL;DR: A two-way coupled aeroelastic model of a plunging spanwise flexible wing is presented, suggesting that the wing aspect ratio of the abstracted passerine and goose models corresponds to the optimal aeroElastic response, generating the highest thrust while minimizing the power required to flap the wings.
Abstract: Flying animals possess flexible wings that deform during flight. The chordwise flexibility alters the wing shape, affecting the effective angle of attack and hence the surrounding aerodynamics. However, the effects of spanwise flexibility on the locomotion are inadequately understood. Here, we present a two-way coupled aeroelastic model of a plunging spanwise flexible wing. The aerodynamics is modelled with a two-dimensional, unsteady, incompressible potential flow model, evaluated at each spanwise location of the wing. The two-way coupling is realized by considering the transverse displacement as the effective plunge under the dynamic balance of wing inertia, elastic restoring force and aerodynamic force. The thrust is a result of the competition between the enhancement due to wing deformation and induced drag. The results for a purely plunging spanwise flexible wing agree well with experimental and high-fidelity numerical results from the literature. Our analysis suggests that the wing aspect ratio of the abstracted passerine and goose models corresponds to the optimal aeroelastic response, generating the highest thrust while minimizing the power required to flap the wings. At these optimal aspect ratios, the flapping frequency is near the first spanwise natural frequency of the wing, suggesting that these birds may benefit from the resonance to generate thrust.

15 citations

01 Jan 1975
TL;DR: In this article, the authors trace the origins of helicopter drag and show that the problem (primarily due to bluff body flow separation) can be solved by the adoption of a comprehensive research and development plan.
Abstract: Current helicopters have parasite drag levels 6 to 10 times as great as fixed wing aircraft. The commensurate poor cruise efficiency results in a substantial degradation of potential mission capability. The paper traces the origins of helicopter drag and shows that the problem (primarily due to bluff body flow separation) can be solved by the adoption of a comprehensive research and development plan. This plan, known as the Fuselage Design Methodology, comprises both nonaerodynamic and aerodynamic aspects. The aerodynamics are discussed in detail and experimental and analytical programs are described which will lead to a solution of the bluff body problem. Some recent results of work conducted at the Naval Ship Research and Development Center (NSRDC) are presented to illustrate these programs. It is concluded that a 75-per cent reduction of helicopter drag is possible by the full implementation of the Fuselage Design Methodology.

15 citations

Proceedings ArticleDOI
24 Jun 2013
TL;DR: In this paper, an experimental study on droplet deformation and breakup near the leading edge of an airfoil was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain.
Abstract: This work presents results of an experimental study on droplet deformation and breakup near the leading edge of an airfoil. The experiment was conducted in the rotating rig test cell at the Instituto Nacional de Tecnica Aeroespacial (INTA) in Madrid, Spain. An airfoil model was placed at the end of the rotating arm and a monosize droplet generator produced droplets that fell from above, perpendicular to the path of the airfoil. The interaction between the droplets and the airfoil was captured with high speed imaging and allowed observation of droplet deformation and breakup as the droplet approached the airfoil near the stagnation line. Image processing software was used to measure the position of the droplet centroid, equivalent diameter, perimeter, area, and the major and minor axes of an ellipse superimposed over the deforming droplet. The horizontal and vertical displacement of each droplet against time was also measured, and the velocity, acceleration, Weber number, Bond number, Reynolds number, and the drag coefficients were calculated along the path of the droplet to the beginning of breakup. Results are presented and discussed for drag coefficients of droplets with diameters in the range of 300 to 1800 micrometers, and airfoil velocities of 50, 70 and 90 meters/second. The effect of droplet oscillation on the drag coefficient is discussed.

15 citations

01 Jan 1956
TL;DR: In this article, the problem of shaping an adjoining fuselage so that the combination will have a low wave drag is considered, but only fuselages that can be simulated by singularities (multipoles) distributed along the body axis are studied.
Abstract: For a given wing and supersonic Mach number, the problem of shaping an adjoining fuselage so that the combination will have a low wave drag is considered. Only fuselages that can be simulated by singularities (multipoles) distributed along the body axis are studied. However, the optimum variations of such singularities are completely specified in terms of the given wing geometry. An application is made to an elliptic wing having a biconvex section, a thickness-chord ratio equal to 0.05 at the root, and an aspect ratio equal to 3. A comparison of the theoretical results with a wind-tunnel experiment is also presented.

15 citations

Proceedings ArticleDOI
28 Jun 2010
TL;DR: In this article, a swept-back grid-fin configuration was proposed to further reduce the unfavorable effects of the transonic choking phenomenon by adding a 20° sharp angle to the leading edges of the lattice walls.
Abstract: A swept-back grid-fin configuration was proposed in a previous study as a mean for reducing the drag associated to flow choking in the lattice cells at transonic speeds. The current follow-on study aims to further reduce the unfavorable effects of the transonic choking phenomenon by adding a 20° sharp angle to the leading edges of the lattice walls. Viscous computational fluid dynamic simulations were performed to investigate the flow of an ogive-cylinder body with conventional and with swept-back grid fins with sharp leading edges at transonic and supersonic speeds and zero angle of attack. These data were further validated with wind-tunnel measurements in the transonic regime of models of the two types of fin. The results indicate that swept-back grid fins with sharp leading edges offer a significant drag reduction.

15 citations


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