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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: In this article, the flight of a small bird under the influence of the ground effect is numerically investigated with a complete three-dimensional model including the bird's body and wings.
Abstract: The flight of a small bird under the influence of the ground effect is numerically investigated with a complete three-dimensional model including the bird's body and wings. The flight mode is not the conventional steady gliding flight but an unsteady flight consisting of flapping, twisting, and folding motions. As the bird approaches the ground, the average lift force gradually increases while the average drag force decreases. At a particular distance, the average lift force increases by approximately 47%, whereas the average drag force decreases by nearly 20%, relative to the absence of the ground effect. Because of the ground, the improved aerodynamic performance in flapping flight is much more significant than in steady flight, in which the modification of the lift-drag ratio is typically less than 10%. On the basis of the flow field, regardless of the presence or absence of the ground, there exists no evidence for an obstruction of a wing-tip vortex, which is a remarkable phenomenon and accounts for the improved performance in steady flight. The extent of the region of high pressure beneath the wing in the near-ground case seems to surpass that in the far-ground case, accounting for the greater lift and thrust forces in the near-ground case. This air cushion beneath the wing, known as the cram effect, is the dominant factor of the ground effect on a flapping bird.

26 citations

Proceedings ArticleDOI
05 Jan 2004
TL;DR: In this article, a numerical treatment in Prandtl lifting-line theory of the nonlinearity associated with a 2D lift curve, when the local incidence is larger than the incidence of maximum lift, is proposed.
Abstract: Numerical treatment in Prandtl lifting-line theory of the nonlinearity associated with a 2-D lift curve, when the local incidence is larger than the incidence of maximum lift, is proposed. It is shown that the use of an artificial viscosity term makes the solution unique and allows the iterative method to converge to a physically meaningful solution, that is in agreement with the exact solution for the test case. The design and analysis of winglets is presented. The winglets considered are small fences placed upward at the tip of the wing to improve the wing efficiency by decreasing the induced drag. The effect of yaw on a wing equipped with such optimal winglets indicates that they provide weathercock stability.

26 citations

Journal ArticleDOI
Tim Lee1
TL;DR: In this paper, the aerodynamic and near-wake characteristics of a NACA 0012 airfoil equipped with perforated Gurney-type flaps of different heights and porosities at Re = 2.32 × 10 5.
Abstract: A low-speed wind-tunnel experiment was conducted to examine the aerodynamic and near-wake characteristics of a NACA 0012 airfoil equipped with perforated Gurney-type flaps of different heights and porosities at Re = 2.32 × 10 5 . The perforation-generated jet flows disrupted the periodic wake behind the flap, reducing the effective camber effects, and led to a reduced lift and drag coefficient as well as a less negative peak C m , compared with the solid flap. The magnitude of C l,max , C d , and C m,peak decreased with increasing amount of perforation. The decrease in drag, however, outweighed the loss in lift and rendered an improved lift-to-drag ratio. The reduction of drag alongside the lowered lift was found to be closely coupled to the characteristics of the unsteady wake. A significantly narrowed extent of the unsteady wake with a weakened fluctuating intensity was observed.

26 citations

Proceedings ArticleDOI
06 Jun 1988
TL;DR: In this paper, a computer program is developed that optimizes span loads with structural weight taken into account, and the program optimizes the twist distribution to minimize a combination of wing drag and weight, based on a Trefftz plane induced drag analysis and on an empirical profile drag estimation.
Abstract: A computer program has been developed that optimizes spanloads with structural weight taken into account. The program optimizes the twist distribution to minimize a combination of wing drag and weight. The wing drag is based on a Trefftz plane induced drag analysis and on an empirical profile drag estimation. The wing weight is based on a simple beam model where weight is based on bending strength design for a critical condition spanload. The program can be used to analyze multiple non-planer lifting surface configurations with realistic constraints such as trim and material limitations.

26 citations

Patent
13 May 1996
TL;DR: A lifting fuselage/wing aircraft having low drag at a selected cruise condition is defined in this article, where the aircraft includes a lift fuselage having a cross-section constituting an airfoil in a majority of vertical planes taken parallel to the flight direction and an aspect ratio (AR f ) of 0.33 to 1.10.
Abstract: A lifting-fuselage/wing aircraft having low drag at a selected cruise condition. The aircraft includes (a) a lifting fuselage having a cross-section constituting an airfoil in a majority of vertical planes taken parallel to the flight direction and an aspect ratio (AR f ) of 0.33 to 1.10; (b) wings fixed to the fuselage having an aspect ratio (AR w ) of at least 5.0; (c) a mechanism controlling aircraft attitude; and (d) a mechanism propelling the aircraft; wherein the wings and fuselage produce lift in varying proportions depending upon flight conditions as follows: (i) the aircraft has a cruise design point in which the fuselage lift coefficient (C LF ) is 0.08 or less, and (ii) the fuselage lift coefficient is at least 0.50 at an angle of attack (α LZo ) of 10°, in level flight at sea level (ISA) with all movable lift enhancing devices retracted.

26 citations


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