Showing papers on "Lift-induced drag published in 1973"
TL;DR: In this paper, the effect of wing span loading on the development of fully rolled-up wing trailing vortices is discussed, and it is shown that parabolic wing loadings produce potential flow maximum core rotary speeds which are finite and less than 50% greater than the downwash speeds at the plane of symmetry.
Abstract: The effect of wing span loading on the development of fully rolled-up wing trailing vortices is discussed. It is shown that parabolic wing loadings produce potential flow maximum core rotary speeds which are finite and less than 50% greater than the downwash speeds at the plane of symmetry. The development of turbulent cores is analyzed and core growth is predicted to occur as the two-thirds power of time, whereas the peak velocities fall off as the inverse one-third power. Axial flow effects of the wing profile drag and lifting system are shown to lead to axial jets on the vortex axis which may either follow the aircraft or exceed the freestream velocity, depending on the ratio of profile drag to enduced drag.
60 citations
TL;DR: In this article, the force acting on a fish-like body with combined thickness and lifting effects is analyzed on the assumption of inviscid flow and a general expression is developed for the pressure force on the body, which is analogous to the momentum-flux analysis for nonlifting bodies in classical hydrodynamics.
Abstract: The force acting on a fish-like body with combined thickness and lifting effects is analysed on the assumption of inviscid flow A general expression is developed for the pressure force on the body, which is analogous to the momentum-flux analysis for non-lifting bodies in classical hydrodynamics For bodies with constant volume, the mean drag (or propulsive) force is expressed in terms of a contour integral around the vortex sheet behind the body Attention is focused on the case of steady-state motion with constant angle of attack, and the induced drag is analysed for finned axisymmetric bodies using the slender-body approximation developed by Newman & Wu (1973) Unlike earlier results of Lighthill (1970), the lift–drag ratio in this case depends on the body thickness
41 citations
TL;DR: In this article, a 10% scale-model disk-gap-band-type parachute assemblies trailing in the Viking forebody wake were conducted over the range of Mach 0.2 to 2.6.
Abstract: Several experimental investigations to obtain the drag performance of 10% scale-model disk-gap-band-type parachute assemblies trailing in the Viking forebody wake were conducted over the range of Mach 0.2 to 2.6. The wind-tunnel tests varied both the canopy trailing distance and ratio of suspension line length to canopy diameter. The data obtained permitted optimization of both parameters. Parachute drag performance in the forebody wake is markedly degraded transonically beginning at Mach 0.6, reaching a minimum value at Mach 1.0, then approaches the subsonic value for the selected configuration as Mach number is increased to 1.4. Further increase in Mach number causes the drag coefficient to again decline. A 20% increase in parachute-alone transonic drag coefficient was obtained by increasing suspension-line length ratio from 1.16 to 1.73.
32 citations
TL;DR: In this paper, the span-wise aerodynamic loading of a wing with minimum induced drag was derived for prescribed lift and root-bending moment, in the case that the lift and its moment of inertia about the longitudinal axis of the aircraft are given.
Abstract: The spanwise aerodynamic loading of wings having minimum induced drag is derived for prescribed lift and root-bending moment. THis problem is an alternative to Prandtl's solution for the case that the lift and its moment of inertia about the longitudinal axis of the aircraft are given.
32 citations
01 Jan 1973
TL;DR: In this article, a flight and wind tunnel investigation was conducted to determine the effects of Reynolds number on the installed boattail drag of an underwing nacelle of an F-106B aircraft.
Abstract: A flight and wind tunnel investigation was conducted to determine the effects of Reynolds number on the installed boattail drag of an underwing nacelle. Tests were run on a modified F-106B aircraft and 0.05 and 0.22 scale wind tunnel models. Tests were conducted at Mach numbers of 0.6 and 0.9 and over a 16 to 1 range of Reynolds numbers. Highest drag was obtained at intermediate Reynolds numbers corresponding to about the lowest flight values and that of the 0.22 scale model. Significantly lower drag was obtained at both higher and lower Reynolds numbers.
14 citations
TL;DR: In this paper, the induced drag for a hemi-circular front view wing with both tips in close proximity to the ground surface is considered. And the exact expression of the span efficiency factor is discussed analytically and numerically.
Abstract: The induced drag is considered for a hemi-circular front view wing with both tips in close proximity to the ground surface. The integral equation is exactly solved using Sohngen's inversion formula. Assuming an optimum downwash distribution, the exact expression of the span-efficiencyfactor is discussed analytically and numerically.
11 citations
01 May 1973
TL;DR: In this paper, the effects of variations in fineness ratio and closure ratio on the boattail drag of circular arc afterbody models were investigated at static conditions and at Mach numbers from 0.40 to 1.30.
Abstract: The effects of variations in fineness ratio and closure ratio on the boattail drag of circular-arc afterbody models were investigated at static conditions and at Mach numbers from 0.40 to 1.30. Jet total-pressure ratio was varied from jet off to about 6, depending on Mach number. Reynolds number based on model maximum diameter varied from about 1.2 million to 2.18 million. Angle of attack was varied from -4 deg to 8 deg. The results indicate that, at subsonic speeds before the drag rise and at a scheduled pressure ratio, the total drag (pressure plus calculated skin friction) is approximately equal for configurations with the same closure ratio. Also, for configurations with the same closure ratio, increasing fineness ratio results in an increased drag-rise Mach number; and for configurations with the same fineness ratio, increasing closure ratio results in an increased drag-rise Mach number.
10 citations
TL;DR: The purpose of this investigation is to develop a suitable numerical method for solving the problem of completely arbitrary lifting wings flying in the close proximity to arbitrary planar or nonplanar ground.
Abstract: THE search for new high-speed ground transportation water and rough terrain vehicles has spread in many directions. One of these directions involves the use of aerodynamic lift to support and stabilize a high-speed vehicle above a planar or nonplanar (regular or irregular) ground surface. The ram wing and the terrafoil are the most popular names associated with this mode of transportation. A ram wing can be described as a vehicle which is geometrically similar to a large low-aspect-ratio airfoil flying close to the ground and is subject to aerodynamic ground effects. A detailed description of a terrafoil vehicle is presented in Ref. 1. In general, it can be described as a tandem winged vehicle subject to close ground effect and which aerodynamically interacts with a surface or guideway to achieve static and dynamic stability. The ram wing and terrafoil concepts for multiterrain travel have several advantages over other proposed guided and multiterrain vehicles, such as the air-cushion vehicle. Among these advantages are: 1) the utilization of ground augmented dynamic lift at high speeds, 2) the reduction in induced aerodynamic drag due to the presence of ground effect, 3) the reduction of wave and spray drag over water since these vehicles will in general (and particularly at high speeds) fly appreciably higher than the corresponding air-cushion vehicle, 4) the elimination of momentum or sink drag, which is the equivalent of induced drag for a wing, 5) the capability of being integrated with a captured air-bubble lift augmentation system, and 6) the capability for negotiating obstacles or drastic changes in height above the ground to facilitate travel over very rough terrain. There have been, however, some major difficulties impeding the development of these vehicles for use in highspeed surface transportation. One of these difficulties has been the absence of analytical or numerical methods for determining the flowfield about completely arbitrary nonplanar wings in the presence of any arbitrary nonplanar ground situation. Another difficulty stems from the fact that there has been a lack of investigations into the static and dynamic stability characteristics of three-dimensional wings in arbitrary ground effect. It is, therefore, the purpose of this investigation to develop a suitable numerical method for solving the problem of completely arbitrary lifting wings flying in the close proximity to arbitrary planar or nonplanar ground. A fu-
9 citations
8 citations
01 May 1973
TL;DR: In this article, the results of wind tunnel tests of three parachute configurations in the wake of a cone-cylinder are presented, and the results are correlated with some published subsonic and supersonic data.
Abstract: The results of wind tunnel tests of three parachute configurations in the wake of a cone-cylinder are presented. The tests were conducted to extend the drag and stability characteristics of selected parachutes through the transonic speed range. The configurations studied were the hemisflo ribbon, the cross, and the disk-gap-band types. The results are presented as the variation of the parachute drag coefficient with Mach number. General stability characteristics of the parachutes are discussed. The results are then correlated with some published subsonic and supersonic data.
TL;DR: In this paper, the problem of a non-planar wing of finite span very close to the ground is considered by the method of matched asymptotic expansions, which is valid for small ground clearance and moderately small aspect ratio, for the case when the configuration of the wing projected onto a transverse plane normal to the free stream is elliptic.
Abstract: The problem of a non-planar wing of finite span very close to the ground is considered by the method of matched asymptotic expansions. This method is based on the work of Widnall and Barrows, in which a planar wing very close to the ground was examined in detail. A simple analytic solution, to first-order approximation, is obtained for a non-planar wing which is uncambered. Expressions for the lift coefficient, induced angle and induced drag coefficient, which are valid for small ground clearance and moderately small aspect ratio, are derived for the case when the configuration of the wing projected onto a transverse plane normal to the free stream is elliptic. The problem of the optimum lift distribution around the wing and the rolling-moment coefficient for the inclined flat wing are discussed. The distribution of camber and of aerofoil angle of attack is given analytically for an optimally loaded non-planar wing, to first-order approximation. Moreover, it is seen that, to first-order approximation, the aerodynamic forces given for the small aspect ratio are independent of the wing planform and depend only on the wing configuration at the trailing edge projected onto a transverse plane.
TL;DR: In this paper, the induced drag of a front view wing with both tips in close proximity to the ground surface was considered for a hemicircular front-view wing with the lifting line theory.
Abstract: The induced drag is considered for a hemicircular front view wing with both tips in close proximity to the ground surface, using the lifting line theory. The integral equation is exactly treated and, assuming that the lift distribution is optimum, the exact expression of the span efficiency factor is obtained. Also, the lift distribution is discussed analytically and numerically.
01 Jun 1973
TL;DR: In this article, an experimental investigation was conducted in an 11- by 11-foot transonic wind tunnel to study the lift, drag and stability characteristics of a 0.087-scale model of an operational airplane fitted with an oblique wing.
Abstract: An experimental investigation was conducted in an 11- by 11-foot transonic wind tunnel to study the lift, drag and stability characteristics of a 0.087-scale model of an operational airplane fitted with an oblique wing. The model wing was of elliptical planform with an unswept aspect ratio of 12.7 and a thickness of 10 percent. All other external geometric features of the model were scaled to the basic full size operational airplane with the engine inlet faired closed. Longitudinal and lateral-directional stability data were obtained with the wing at sweep angles of 0 deg, 45 deg and 60 deg Test Mach numbers ranged from 0.6 to 1.4 deg Angles of attack were between minus 4 deg and 8 deg at zero sideslip. Angles of sideslip were between plus and minus 4 degrees for two angles of attack depending upon the wing configuration. Tests were conducted at a Reynolds number of 6 million per foot except for a few runs when balance capacity limited the Reynolds number to 4 million per foot.
28 Feb 1973
01 May 1973
TL;DR: In this paper, the authors describe a lifting surface theory for calculating the aerodynamic characteristics of jet-flapped wings based on a finite-element scheme -the method of elementary vortex distribution or the EVD method, which is represented by a set of overlapped elementary vortex distributions.
Abstract: : The report describes a lifting surface theory for calculating the aerodynamic characteristics of jet-flapped wings. Based on a finite-element scheme - the method of Elementary Vortex Distribution or the EVD method, the wing and jet sheet are represented by a set of overlapped elementary vortex distributions. A solution is obtained by satisfying a set of mixed-type boundary conditions on both the wing and jet sheet. The EVD method, as described, provides the following: spanwise and chordwise loading; spanwise variation of induced drag; a capability to investigate the effects of part span flaps, part span blowing, rolling, yawing, pitching, and sideslip; and total lift and induced drag (momentum method), pitching moment, yawing and rolling moments, and side force. (Modified author abstract)
01 May 1973
TL;DR: In this paper, a high speed wind tunnel test has been conducted to determine the effect on cruise drag for installing larger JT8D Refan engine nacelles on the Douglas DC-9.
Abstract: A high speed wind tunnel test has been conducted to determine the effect on cruise drag for installing larger JT8D Refan engine nacelles on the Douglas DC-9. Drag data and wing- and nacelle/pylon/fuselage-channel pressure data are presented. Reduced pylon spares, required to minimize effects of the nacelle installation on low-speed deep stall, were investigated. The reduce span pylons resulted in no adverse interference effects. At typical cruise Mach numbers the measured penalty for the Refan installation was less than estimated due to a favorable effect of the larger entering engine stream tube suppressing the wing upper-surface velocities with subsequent wing compressibility drag reduction. Channel pressures show no shock waves or boundary layer separations.
01 Jan 1973
TL;DR: In this paper, the authors considered the problem of a vehicle entering and passing through a tunnel and showed that the incompressible approximation provides the basic solution and the modifications from this basic solution caused by the compressible wave effects.
Abstract: The problem of a vehicle entering and passing through a tunnel is considered. It is shown that the incompressible approximation provides the basic solution and the modifications from this basic solution caused by the compressible wave effects. The effect on the aerodynamics of different propulsion systems is described. The effects of vehicle length, tunnel entrance configurations, and air shafts on vehicle drag and tunnel flow field are considered. The conditions under which the waves generated by the vehicle might escape from the tunnel exit to cause an "exit boom" are determined.
01 Jan 1973
TL;DR: In this paper, a design technique for rapidly computing lift, induced drag, and spanwise loading of unswept jet flap wings of arbitrary thickness, chord, twist, blowing, and jet angle, including discontinuities, is presented.
Abstract: Paper presents a design technique for rapidly computing lift, induced drag, and spanwise loading of unswept jet flap wings of arbitrary thickness, chord, twist, blowing, and jet angle, including discontinuities. Linear theory is used, extending Spence's method for elliptically loaded jet flap wings. Curves for uniformly blown rectangular wings are presented for direct performance estimation. Arbitrary planforms require a simple computer program. Method of reducing wing to equivalent stretched, twisted, unblown planform for hand calculation is also given. Results correlate with limited existing data, and show lifting line theory is reasonable down to aspect ratios of 5.