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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
M. S. Howe1
TL;DR: In this paper, an analysis of the force and moment exerted on a rigid body in unsteady motion in a uniform incompressible, viscous or inviscid fluid is made, and integral formulae are derived which express the forces and moments in terms of the velocity and vorticity of the fluid and the velocity of the body.
Abstract: An analysis is made of the force and moment exerted on a rigid body in unsteady motion in a uniform incompressible, viscous or inviscid fluid. Integral formulae are derived which express the force and moment in terms of the velocity and vorticity of the fluid and the velocity of the body. The results extend a previous investigation of this problem (1), and permit the identification of the separate influences of added mass, normal stresses induced by free vorticity, and viscous skin friction. Illustrative applications are made to airfoil theory, to the calculation of the induced drag of a vortex street and the force on a cylinder moving in a slowly varying rotational mean flow, and to the determination of the viscous drag experienced by solid spheres and bubbles. The theory gives a direct prediction of the drag on a bubble in high-Reynolds-number motion, in contrast to the usual approach in which the drag is determined by equating the viscous dissipation to the work done by the drag force.

112 citations

Proceedings ArticleDOI
01 Dec 1997
TL;DR: Progress on issues such as instability studies, nose-bluntness and angle-of-attack effects, and leading-edge-contamination problems from theoretical, computational, and experimental points of view are discussed.
Abstract: This paper discusses progress on issues such as instability studies, nose-bluntness and angle-of-attack effects, and leading-edge-contamination problems from theoretical, computational, and experimental points of view. Also included is a review of wind-tunnel and flight data, including high-Re flight transition data, the levels of noise in flight and in wind tunnels, and how noise levels can affect parametric trends. A review of work done on drag accounting and the role of viscous drag for hypersonic vehicles is also provided.

110 citations

Journal ArticleDOI
TL;DR: In this article, the authors identify the differences between two commonly used definitions of span efficiency and show that for the case of airfoil sections and finite wings at chordwise Reynolds numbers less than 10 5, neither one has values close to those commonly assumed in the aeronautics literature.
Abstract: Elegant and inviscid analytical theory can predict the induced drag on lifting wings of finite span. The theoretical prediction is then often modified by multiplication with a dimensionless coefficient for which the departure from a value of 1 is used as a way to incorporate realistic and necessary departures from the idealized model. Unfortunately, there are conflicting definitions of these dimensionless coefficients, often known as span efficiencies, so that even if numerical values are assigned in a clear and transparent fashion, their application and validity remain unclear. Here, the differences between two commonly used definitions of span efficiency are identified and it is shown that for the case of airfoil sections and finite wings at chordwise Reynolds numbers less than 10 5 , neither one has values close to those commonly assumed in the aeronautics literature. The cause of these significant viscous modifications to inviscid theory is traced to the movement of separation points from the trailing edge of real airfoils. A modified nomenclature is suggested to reduce the likelihood of confusion, and appropriate formulations for the drag of streamlined bodies in viscous flows at moderate Reynolds number are considered, with application to small-scale flying devices, both natural and engineered.

109 citations

Journal ArticleDOI
TL;DR: In this paper, a method for direct numerical simulation of polymer-induced friction drag reduction in turbulent boundary layers is described, where the effect of the polymer additives that induce spatial variations of skin-friction drag is included in the momentum equation through a continuum constitutive model for the viscoelastic stress, based on the evolution of a parameter describing the fluid microstructure.
Abstract: We describe a method for direct numerical simulation of polymer-induced friction drag reduction in turbulent boundary layers. The effect of the polymer additives that induce spatial variations of skin-friction drag is included in the momentum equation through a continuum constitutive model for the viscoelastic stress, which is based on the evolution of a parameter describing the fluid microstructure. We demonstrate that the turbulence structure and polymer microstructure evolve asynchronously as one moves in the streamwise direction. We observe an initial development length, which is followed by a quasisteady region where variations in drag reduction are weak. High drag reduction behavior can be present at short downstream distances from the inflow plane.

109 citations

Journal ArticleDOI
TL;DR: The three-dimensional flow structure of a tip vortex in the near wake of both a rectangular, square-tipped NACA 0015 and a high-lift cambered airfoil was investigated by using a seven-hole pressure probe at Re = 2.01 x 10 5.
Abstract: The three-dimensional flow structure of a tip vortex in the near wake of both a rectangular, square-tipped NACA 0015 airfoil and a high-lift cambered airfoil was investigated by using a seven-hole pressure probe at Re = 2.01 x 10 5 . Lift-induced drag was computed based on vorticity and was compared with force-balance data. For both the airfoils tested, the vortex strength reached a maximum immediately behind the trailing edge and remained nearly constant up to two chord lengths downstream. As the airfoil incidence increased, the increase in the lift force resulted in a basically linear increase in the vortex strength and the peak values of the tangential velocity and vorticity, whereas the vortex radius did not appear to have a clear dependence on the vortex strength. Depending on the airfoil incidence, the core axial velocity could be wake-like or jet-like. The normalized circulation within the inner region of the nearly axisymmetric tip vortex exhibited a universal, or self-similar, structure. The NACA 0015 airfoil, however, possessed smaller tangential velocities but similar vortex core diameters compared to those of a cambered airfoil

108 citations


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