Showing papers on "Lift-induced drag published in 1968"
TL;DR: A technique for training pigeons to fly in a tilting wind tunnel, and a method of determining lift and drag in gliding flight is explained, which shows that changes of wing area and shape keep it near its maximum, up to speeds at least twice the minimum gliding speed.
Abstract: 1. A technique for training pigeons to fly in a tilting wind tunnel is described, and a method of determining lift and drag in gliding flight is explained. 2. Drag measurements were made on wingless bodies and preserved feet in supplementary experiments. The results were used to analyse the measured total drag of live pigeons into ( a ) body drag, ( b ) foot drag, ( c ) induced drag, and ( d ) wing profile drag. 3. As speed is increased, gliding pigeons drastically reduce their wing span, wing area and aspect ratio. The increased induced drag resulting from this is more than offset by a very large reduction in wing profile drag. 4. Although the lift: drag ratio is at best 5.5-6.0, changes of wing area and shape keep it near its maximum, up to speeds at least twice the minimum gliding speed.
198 citations
01 Aug 1968
TL;DR: In this paper, the leading edge suction analogy of vortex lift was used to predict delta wing drag by applying of leading edge SUction analogy to vortex lift, and the results showed that the resulting prediction was correct.
Abstract: Sharp edge delta wing drag prediction by application of leading edge suction analogy of vortex lift
67 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
Patent•
22 Jul 1968
TL;DR: In this article, the stabilizing fins and the drag brake were deployed to a position perpendicular to the missile axis to produce aerodynamic drag, as well as rotate the stabilising fins to rotate them.
Abstract: Retractable stabilizing fins and drag brake apparatus having coactive connection between the stabilizing fins and drag brakes. The stabilizing fins when deployed to a position perpendicular to the missile axis present an edge to air stream. The drag brakes when deployed to a position perpendicular to the missile axis produce aerodynamic drag as well as rotate the stabilizing fins to a position to produce aerodynamic drag.
24 citations
17 Jun 1968
TL;DR: In this paper, the authors presented three numerical methods for obtaining the subsonic load distribution on a thin wing of arbitrary twist and camber: NPL, NLR (Netherlands) and BAC (Warton).
Abstract: Independent numerical methods for obtaining the subsonic load distribution on a thin wing of arbitrary twist and camber have been developed at NPL, NLR (Netherlands) and BAC (Warton), The three methods have been studied jointly and their novel features have been reviewed critically. The best solutions by each method show excellent agreement for wings, at uniform incidence, having smooth leading and trailing edges. Spanwise loading, local aerodynamic centres, lift, pitching moment, vortex drag and chordwise loadings are tabulated for circular and rectangular planforms, for a wing of constant chord with hyperbolic leading and trailing edges, and for a tapered sweptback wing. The convergence of the solutions is examined in detail with respect to separate parameters representing the numbers of spanwise integration points and spanwise and chordwise collocation points. The tapered sweptback planform is considered with different amounts and types of artificial central rounding, but the crucial problem of a central kink under lifting conditions remains a subject for research.
16 citations
TL;DR: In this paper, the authors show that the vortex drag factor is closely related to the half-wing spanwise center of pressure on simple planforms without camber or twist, and that lifting-line theory is useless for predicting the spanwise distribution of vortex drag on swept wings.
Abstract: Summary Theoretical data from lifting-surface theory are presented to illustrate (i) that the vortex drag factor is closely related to the half-wing spanwise centre of pressure on simple planforms without camber or twist, (ii) that lifting-line theory is useless for predicting the spanwise distribution of vortex drag on swept wings, (iii) that recent numerical improvements in lifting-surface theory help to reconcile the concepts of wake energy and leading-edge suction in relation to vortex drag.
14 citations
01 Oct 1968
TL;DR: In this paper, it was shown that recessing the base has practically no effect on boattail drag and that the ratio of the amount of base concavity to base radius necessary to achieve maximum base-drag reduction depends on the boattails angle and length.
Abstract: to 0.03, depending on the boattail, and hence a reduction in base drag. For a given boattail, base drag decreases with increasing base concavity up to a certain point, but, beyond this point, further concaving the base has little or no effect. The ratio of the amount of base concavity to base radius necessary to achieve maximum base-drag reduction depends on the boattail angle and length. Recessing the base has practically no effect on boattail drag. INTRODUCTION The base drag of an aircraft, unpowered projectile, or missile with a blunt base Considerable work has been can represent a large portion of the total drag; and the effectiveness of ways of reducing this drag has been the objective of many investigations. done on the reduction of base drag by the base-bleed and splitter-plate methods (e&, see refs. 1 and 2). One method of interest, on which a lesser amount of work has been done, particularly for axisymmetric flow, is recessing the base. The present work
12 citations
Book•
01 Jan 1968
TL;DR: User manual for computer program 55VD for computation of minimum induced drag and load distribution of nonplanar wings.
Abstract: User manual for computer program 55VD for computation of minimum induced drag and load distribution of nonplanar wings
12 citations
Patent•
19 Feb 1968
12 citations
5 citations
01 Nov 1968
01 Mar 1968
TL;DR: In this article, a wind tunnel investigation of techniques for reducing cowl drag of external compression inlet at Mach 2.49 was conducted, and the results showed that the inlet inlet can be reduced by approximately 50% at the expense of increased wind tunnel drag.
Abstract: Wind tunnel investigation of techniques for reducing cowl drag of external compression inlet at Mach 2.49
01 Oct 1968
TL;DR: Aeroelastic divergence characteristics of moveable control surfaces, including drag loadings, are analyzed in this article. But the authors focus on a single control surface and do not consider the effect of other surfaces.
Abstract: Aeroelastic divergence characteristics of moveable control surfaces, including drag loadings
01 Apr 1968
TL;DR: In this article, a wind tunnel model one component magnetic support and balance system for sphere drag investigation at subsonic Mach numbers is presented, which is based on the one component magnetometer.
Abstract: Wind tunnel model one component magnetic support and balance system for sphere drag investigation at subsonic Mach numbers
01 Nov 1968
TL;DR: In this article, the authors present a user manual for computer program 55VD for computation of minimum induced drag and load distribution of nonplanar wings for non-planar aircraft.
Abstract: User manual for computer program 55VD for computation of minimum induced drag and load distribution of nonplanar wings
01 Dec 1968
TL;DR: In this article, the aerodynamic characteristics of these configurations were obtained at Mach numbers 1.5, 2.0 and 3.0 at angles of attack from -12 to 12 deg and Reynolds numbers, based on the 10-in. model root chord, from 1,300,000 to 6,000,000.
Abstract: : Tests were conducted in a 40-in. supersonic wind tunnel on a 70-deg- sweep delta wing. A gap between the leading edge and main body was varied from a sealed condition to a nominal 0.030-in. opening for three leading edges of various camber. The aerodynamic characteristics of these configurations were obtained at Mach numbers 1.5, 2.0, and 3.0 at angles of attack from -12 to 12 deg and Reynolds numbers, based on the 10-in. model root chord, from 1,300,000 to 6,000,000. Results are presented showing the variation in lift/drag for various combinations of gap width and leading-edge camber.
01 Jan 1968
TL;DR: In this article, minimum drag airfoils at moderate supersonic speeds are determined using second-order theory using second order theory under the assumption that the length is prescribed: given thickness and given enclosed area.
Abstract: : Minimum drag airfoils at moderate supersonic speeds are determined using second-order theory. Two cases are investigated under the assumption that the length is prescribed: (a) given thickness and (b) given enclosed area. If the thickness is given, the minimum drag airfoil is a diamond shape. If the enclosed area is given, the minimum drag airfoil is biconvex. In both cases, the maximum thickness occurs in the rear half of the airfoil; while, if the linear theory is employed, it occurs exactly at midchord. (Author)
TL;DR: In this article, the lift and drag of a half-circular cross-section cone mounted above or below a delta wing of zero thickness with subsonic leading edges and placed in a supersonic flow was studied using the slender-body theory.
Abstract: Configurations, composed of a cone with a half-circular cross-section mounted above or below a delta wing of zero thickness with subsonic leading edges and placed in a supersonic flow, are studied using the slender-body theory in order to determine their lift and drag characteristics. These are compared to the lift and drag of configurations composed of the same wing and a symmetrically disposed circular cone with equal volume as the half-cone. The comparison is made to investigate whether it is possible to attain better lift efficiency by placing the body on one side of the wing. For configurations having a body diameter-wing span ratio larger than approximately 0.45, a disposition of a half-cone on one side of the delta wing shows a drag reduction at a given lift, and therefore a higher value of (CL/CD)max, compared to the corresponding symmetrical combination. However, the high-wing combination is preferable to the low-wing, since lower angles of incidence are needed to attain a certain CL. If the body diameter-wing span ratio is less than this value, the symmetrical system appears to be more favourable. The lift curve slope dCL/dα of the asymmetrical configurations studied is larger than that of the symmetrical configurations.
15 Jan 1968
TL;DR: In this article, a wind-tunnel investigation has been conducted in the Langley High-Speed 7- by 10-Foot Tunnel to determine the buffet and static aerodynamic characteristics of a systematic wing series at Mach numbers ranging from 0.23 to 0.94.
Abstract: A wind-tunnel investigation has been conducted in the Langley High-Speed 7- by 10-Foot Tunnel to determine the buffet and static aerodynamic characteristics of a systematic wing series at Mach numbers ranging from 0.23 to 0.94. The results have indicated that for a given Mach number, the wings which display superior aerodynamic efficiency characteristics generally display the highest buffet free lift coefficient. The characteristics exhibited by the wings which were considered have indicated that correlations can be made between the onset of buffet and selected divergences in the static aerodynamic characteristics. Axial force has been found to be the most sensitive static component to the onset of buffeting.
01 Mar 1968
TL;DR: In this article, volume addition effects on leeward surface of high lift drag ratio winged body at hypersonic speeds were studied for a single-winged aircraft at high speed.
Abstract: Volume addition effects on leeward surface of high lift drag ratio winged body at hypersonic speeds