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.

Turbulent drag reduction using riblets on a supercritical airfoil at transonic speeds

Abstract: Numerous studies have shown that viscous drag reduction of 4-8% at low speeds can be achieved in simple two-dimensional flows at wind-tunnel Reynolds numbers. Because of the encouraging benefits realized at low speeds, an evaluation of riblet effectiveness at subsonic and transonic speeds, both in wind tunnels and flight, has been reported. Realistic applications involve, among other factors, pressure gradient (eg, airfoil and wing) and three-dimensionality. Drag reductions under these conditions are being assessed currently. This paper presents recent results of drag reduction using 3M riblets on a supercritical airfoil at transonic speeds covering an angle of attack range of -0.5 to 1 deg, which is relevant to cruise conditions. (Authors)

Evaluation of installed performance of a wing-tip-mounted pusher turboprop on a semispan wing

Abstract: An exploratory investigation has been conducted at the Langley Research Center to determine the effect of a wing-tip-mounted pusher turboprop on the aerodynamic characteristics of a semispan wing. Tests were conducted on a semispan model with an upswept, untapered wing and an airdriven motor that powered an SR-2 high-speed propeller located on the tip of the wing as a pusher propeller. All tests were conducted at a Mach number of 0.70 over an angle-of-attack range from approximately -2 to 4 deg at a Reynolds number of 3.82 x 10 to the 6th based on the wing reference chord of 13 in. The data indicate that, as a result of locating the propeller behind the wing trailing edge at the wing tip in the crossflow of the wing-tip vortex, it is possible to improve propeller performance and simultaneously reduce the lift-induced drag.

Basic Induced Drag Study of the Joined-Wing Aircraft

Abstract: J OINED-WING configuration was considered for the first time by Prandtl in 1924 [1] The first attempt to build a joinedwing airplane was undertaken by the Moscow Institute of Aviation in the 1940s, when they redesigned a classic biplane called the Polikarpow Po-2 to create the joined-wing airplane [2] More recently, the configuration was studied by Wolkovitch [3] and Kroo and Gallman [4] in the 1980s A project described in [5] was inspired by these works It consisted of a series of wind-tunnel tests with models of a small transport airplane (see Fig 1) The most interesting result obtained in this project was that a greater L=Dwas achieved for negative angles of attack than for positive ones (see Fig 2) This observation suggests that the front wing of the aircraft in a joined-wing configuration should be located on top of the fuselage and the rear wing at the bottom to obtain greater aerodynamic efficiency This complicates the design because it is not possible to use the fin as a pylon for the rear wing and fuselages usually are not particularly high Anyway, this front-high-joinedwing configuration can be considered in cases of small 2–4 seat general aircraft, small transport aircraft, and very large commercial double-deckers Later, in the 1990s, a few papers on the joinedwing configuration were published [6], most of them focusing on mass-strength analysis

Nonlinear Negative Stiffness Wingtip Spring Device for Gust Loads Alleviation

Abstract: A recent consideration in aircraft design is the use of folding wingtips with the aim of enabling higher-aspect-ratio configurations with less induced drag while also meeting airport gate limitations. This study builds on previous work investigating the effect of exploiting the folding wingtips in flight as a device to reduce dynamic gust loads, but now with the introduction of a passive nonlinear negative stiffness hinge spring. A single-degree-of-freedom model and a representative civil jet aircraft aeroelastic model are used to investigate the dynamic gust responses for different hinge device designs. It is found that significant reductions in the dynamic loads are possible.

Conceptual design and evaluation of blended-wing-body aircraft

Abstract: Blended wing body (BWB) aircraft represent a paradigm shift in jet transport aircraft design that promise benefits over conventional aircraft. A method is presented to enable the conceptual design of BWB aircraft, enabling comparison studies with tube-and-wing aircraft (TAW) based on the same top-level requirements and analysis fidelity. The aim of this work is to make comparative studies between the blended-wing-body aircraft and its conventional tube-and-wing counterpart based upon the same design requirements at conceptual level. By developing a novel geometric parametrisation of the blended wing body, the design possibilities have been increased while maintaining straightforward shaping manipulation and robustness. The mass estimation methods that have been implemented are verified and validated to be within approximately 5% of reference blended wing bodies. Drag estimations perform less accurately with drag being overpredicted by approximately 20%. The cause of this over prediction was largely due to empirical corrections for miscellaneous and unaccounted drag sources as well as induced drag predicted by a vortex-lattice method. Test-case BWB and TAW aircraft were formed in the 150, 250 and 400 passenger classes. The comparisons of the resulting aircraft show that the blended wing body have reduced mass, improved aerodynamic efficiency and higher fuel economy. Trends also show that the improvements over tube-and-wing aircraft increase with aircraft size.