Showing papers on "Lift-induced drag published in 1969"

Effects of wingtip-mounted propellers on wing lift and induced drag.

Abstract: It is proposed that aircraft can be designed using propellers at the wingtips in such a way that the L/D ratio can be varied by changing the effective aspect ratio in flight. An experimental program testing a wing with propellers mounted at the wingtips is reported. It is shown that the use of a propeller at the wingtip, turning in the direction opposite to that of the wing vortex, shifts the trailing vortex core outboard, decreases the wing drag coefficient, increases the maximum lift coefficient and increases the effective aspect ratio. Rotating the propeller in the opposite direction has the reverse effect. A functional relationship is shown to exist between ACD/CD and Tcd/CLS-

Trim attitude, lift and drag of the Apollo command module with offset center-of-gravity positions at Mach numbers to 29

Abstract: Free flight test model measurement of drag, lift, and trim in wind tunnel for Apollo command module

Moving surface to reduce drag

Abstract: VEHICLES (E.G., BOATS AND SHIPS) ARE EQUIPPED WITH FREELY MOVABLE SURFACES CONTACTING THE FLUID MEDIUM THROUGH WHICH THE VENICLES TRAVEL. DURING TRAVEL THE SURFACES MOVE IN A DIRECTION OPPOSITE TO THE DIRECTION OF TRAVEL.

Aerodynamic effects of lift-jet and lift-fan inlets in transition flight.

Abstract: An investigation was conducted to determine the force and moment contribution of V/STOL lift-jet and lift-fan inlets in transition based on momentum theory. A lift-jet or lift-fan inlet with its axis perpendicular to the freestream develops strong forces that contribute to positive pitching moments at low forward speeds. The analysis is based on the addition of freestream flow with the static-induced flow at the inlet, which is represented by a sink flow over a hemispherical control surface. The results of the analysis, which provide total inlet force, inlet lift, and drag force, as well as inlet lip force and inlet pitching moment, agree reasonably well with a limited amount of published inlet test data. It is shown that the lift-fan inlet develops significantly greater lift, drag, and moment than the lift-jet inlet at comparable thrust and forward speed. Other comparisons are presented which show the close agreement between inlet drag and total incremental jet-induced drag developed by lift fan-in-fuselage and lift fan-in-wing configurations in transition flight. Nomenclature Ai — inlet area in plane of inlet D = drag Di = inlet momentum drag AD = interference drag increment due to freestream velocity di = inlet diameter F = force L = lift Li = inlet momentum lift AL = interference lift increment due to freestream velocity m = mass flow M = moment Mi = inlet moment of momentum AM = interference moment increment due to freestream velocity p = pressure r = inlet duct radius T = thrust V = velocity v = static inlet velocity y = moment arm of resultant inlet lift J3 = angle of resultant lip force measured from horizontal 6 = coordinate angle = coordinate angle p = air density

Optimum loading on nonplanar wings at minimum induced drag

Abstract: : A numerical technique was developed for computing the optimum spanwise load distribution on nonplanar wings of arbitrary shape. Munk's criterion for minimum induced drag was used. The problem is solved in the two- dimensional Trefftz plane. The two-dimensional shed vortex sheet is assumed to have the same shape as the nonplanar wing from which it was shed. The vortex sheet in the Trefftz plane is subdivided into 2N segments. Each vortex sheet segment is assumed to have a linear vorticity distribution. The velocity induced at N-Q stations is determined with the Biot-Savart law. The problem is then reduced to solving a set of linear algebraic equations. The technique was applied to nonplanar wings with various dihedral angles and locations of the nonplanar wing sections. It was concluded that if the span is the limiting factor then it may be advantageous to use nonplanar wings. On the other hand, if the wing total peripheral length is limited, then the planar wing is always the most desirable configuration, with the highest lift over drag ratio.

A one-component, magnetic support-and-balance system.

Abstract: Wind tunnel model one component magnetic support and balance system for sphere drag investigation at subsonic Mach numbers

Drag reduction due to gas injection through various discrete slots on a three-dimensional wing at Mach 2.01

Abstract: Force measurements in drag reduction by gas injection into turbulent boundary layer through supersonic wing slots

Drag and Performance Characteristics of Several Flexible Aerodynamic Decelerators at Mach Numbers From 1.5 to 6.0

Abstract: : An experimental investigation was conducted at Mach numbers from 1.5 to 6.0 to determine the drag and stability characteristics of several flexible aerodynamic decelerators located in the wake of double-strut-mounted forebodies. Data are presented which show a decrease in drag with an increase in free-stream Mach number and/or a decrease in drag for both guide surface decelerators and for a ballute. Because of differences in calibration techniques, riser line length, and test equipment, a 50- to 70-percent lower value of drag coefficient was obtained on a series of supersonic X decelerators when compared to previous tests. The present data do, however, agree reasonably well with drag data for a full-scale decelerator. An indication of the parachute stability is given in tabular form. All of the present data were obtained at a free-stream dynamic pressure of 1.0 psia and static pressures corresponding to pressure altitudes ranging from 70,000 to 130,000 ft.

An analytical method for predicting the lift and drag for slender sharp-edge delta wings in ground proximity

Abstract: Analytical method for predicting lift and drag for slender sharp-edge delta wings near ground level

Prediction of lift and drag for slender sharp-edge delta wings in ground proximity

Abstract: not considered, ground effect may produce large unexpected alterations in the characteristics of the aircraft during landing and take-off. Therefore, methods for the accurate prediction of the aero- dynamic characteristics of low-aspect-ratio delta wings in ground proximity are neces- sary to the aircraft designer. The present study

Evaluation of the Human Body as an Airfoil

Abstract: : Five subjects were used to determine the lift and drag characteristics of the human body held in a tracking attitude. The effects of eight different parachute pack configurations were tested to evaluate the influence of the pack upon lift and drag.