Topic
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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04 Jan 2010
TL;DR: In this paper, the aerodynamic influence of a half-span model installation is assessed with changing a height of a spacer, which locates between a fuselage and wind tunnel wall.
Abstract: Lowspeed wind tunnel experiment of a high-lift configuration aircraft model JSM (Jaxa high-lift configuration Standard Model) is implemented at 6.5m by 5.5m low-speed wind tunnel in JAXA (JAXA-LWT1). The aerodynamic influence of a half-span model installation is assessed with changing a height of a spacer, which locates between a fuselage and wind tunnel wall. Variation of the aerodynamic characteristics depending on the spacer height in the experiment agrees well with computational results which is assumed wind tunnel wall boundary layer. Aerodynamic coefficients obtained in the experiment become closer to the result of a free-flight computation when the spacer height becomes lower. Local lift distribution estimated by the pressure distribution around the wing cross section changes continuously along spanwise direction when the spacer height increases or decreases. On the other hand, the local drag changes mainly in the inboard area. The variation of the induced drag evaluated by the relation between CD and square of CL shows that an effect of the spacer installation mainly appears as an increment of the effective aspect ratio and resultant changes in slope of the lift curve and reduction of the induced drag. However, an influence of the flow interaction near wind tunnel wall is not negligible. An estimation of desirable height of the spacer for the half-span model experiment is performed by comparing the computational result for the full-span model in free-flight condition and the half-span model installed on non-slip wall condition. Based on the effective aspect ratio of free-flight condition, the spacer height approximately 2 ~ 3 times of the displacement thickness of the floor boundary layer is a best candidate for the spacer height.
38 citations
TL;DR: In this paper, a procedure was developed for the accurate computation of the minimum induced drag of nonplanar wings with pylon-like panels, provided the wing front view consists of straight line segments.
Abstract: A procedure has been developed for the accurate computation of the minimum induced drag of nonplanar wings with pylonlike panels, provided the wing front view consists of straight line segments. As is well known, the induced drag may be expressed as an integral in an auxiliary mapping plane. Previously, the main computational difficulty had been the determination of the Schwarz-Christoffel mapping between the real and the auxiliary planes. By means of the electrostatic analogy to potential flow, the constants of the mapping are determined with a small experimental error by using an analog field plotter. The mapping is then integrated by numerical techniques, and the constants are adjusted until the desired geometry is achieved to any order of accuracy. The induced drag is determined by quadrature and is shown by comparison with known test cases to be accurate to 10~ 4. Comparison of results with earlier approximate solutions (Mangier, Cone) shows that some of the earlier approximate solutions give more favorable predictions (less drag) than the solution derived here. The discrepancies in the earlier work are shown to be due to improper boundary conditions, and some suggestions are made to minimize these effects. The results show a potential reduction of minimum induced drag of less than 1% for a current subsonic jet transport when the pylons are properly loaded.
38 citations
TL;DR: In this paper, minimum induced drag for fixed gross weight and wingspan is obtained from the elliptic lift distribution for steady level flight, but this is not obtained by imposing the constrain.
Abstract: Minimum induced drag for fixed gross weight and wingspan is obtained from the elliptic lift distribution. However, minimum induced drag for steady level flight is not obtained by imposing the const...
38 citations
01 Nov 1967
TL;DR: In this paper, the behavior of wing sections in low-turbulence stream in Reynolds number range from 20,000 to 170,000, and the number of wing segments in the Reynolds number was estimated to be between 170, 000 and 200,000.
Abstract: Airfoil measurements that show behavior of wing sections in low-turbulence stream in Reynolds number range from 20,000 to 170,000
38 citations
TL;DR: In this article, an approach to extend the classical methods by allowing the bending constraints to be imposed at different lift coefficients than that at which induced drag is minimized is presented. But this approach requires the bending constraint at a limiting structural load condition, such as a maneuver lift coefficient.
Abstract: The previous works of Prandtl, Jones, and Klein and Viswanathan addressed the problem of determining the lift distribution that minimizes induced drag for a given lift and specified bending moment. In these formulations, bending moment is considered to be a surrogate for wing weight. These classical methods require the bending constraints to be imposed at the same lift coefficient at which drag is minimized. In practice, however, it is commonly desired to minimize drag at a representative cruise lift coefficient while imposing the bending constraints at a limiting structural load condition, such as a maneuver lift coefficient. This paper presents an approach to extend the classical methods by allowing the bending constraints to be imposed at different lift coefficients than that at which induced drag is minimized. An example for a wing planform similar to that of a Boeing 737 shows that the penalty for optimizing induced drag at the maneuver lift coefficient as implied in the classical methods results in ...
38 citations