Showing papers on "Lift-induced drag published in 1971"

The spacing, position and strength of vortices in the wake of slender cylindrical bodies at large incidence

Abstract: Extensive schlieren studies and yawmeter traverses of the wake behind slender cone-cylinders at large angles of incidence have shown that the flow pattern is generally steady. Under certain flow conditions, however, the wake exhibits an instability which is not understood. For cross-flow Reynolds numbers in the subcritical region the wake can be described in terms of a cross-flow Strouhal number which has a constant value of 0·2 for cross-flow Mach number components (Mc) up to 0·7 and then increases steadily to a value of 0·6 at Mc = 1·6. The strength of the wake vortices varies substantially with Mc, increasing to a maximum at Mc ≈ 0·7 and then decreasing rapidly for higher values of Mc. Schlieren photographs of the wake have been analysed by means of the impulse flow analogy and also by considering the vortices to be part of a yawed infinite vortex street. The impulse flow analogy is shown to be of use in determining the cross-flow Strouhal number but estimates of vortex strength are too high. The Karman vortex street theory combined with the sweepback principle leads to reliable estimates of vortex strength up to Mc = 1·0.Information is given on the spacing, path and strength of the vortices shed from the body for flow conditions varying from incompressible speeds up to Mc = 1·0. Finally this information is used to determine the vortex drag of a two-dimensional circular cylinder below Mc = 1·0.

Control of gliding angle in Rüppell's Griffon Vulture Gyps rüppellii

Abstract: 1. The drag of the frozen, wingless body of a Ruppell9s griffon vulture was measured in a wind tunnel with a simple drag balance. The drag coefficient with feet and neck retracted was 0.43, based on the greatest cross-sectional area of the body. 2. The drag of the body was trebled by fully lowering the feet, and more than quadrupled when the tail was lowered as well, apparently owing to separation of the flow over the back. The drag coefficient of the legs and feet, based on their frontal area, varied from 0.89 to 1.08 in different positions. 3. At low speeds the use of the feet alone should reduce the glide ratio from about 15 to 10, but the airbrake effect becomes progressively more marked at higher speeds. At lower speeds reduction of the wing area produces a greater steepening of the gliding angle, but at the expense of increasing the minimum speed. Increase of induced drag would provide a highly effective gliding angle control at very low speeds, and it is suggested that this is achieved by raising the secondary feathers, which would alter the spanwise lift distribution by transferring a greater proportion of the lift to the primaries.

Theoretical and experimental aerodynamics of the sailwing

Abstract: The sailwing is a unique type of semiflexible foldable wing. A brief description of its construction, basic properties, and some past research, is used to introduce an analytical and experimental study of its aerodynamic characteristics. Emphasis is placed on an approximate structural analysis which treats the nonlinear behavior of the sail deflection. Twodimensional flexible airfoil theory and Prandtl lifting-line theory are used to establish the aerodynamic loading. The results allow prediction of the induced tensions, the nonlinear life curve, induced drag, and aeroelastic divergence of the sail chordwise deflection mode. Selected experimental results are presented for comparison with the theory, along with a brief discussion of the implications of the study regarding flight vehicle applications of the sailwing.

Sting-free drag measurements on ellipsoidal cylinders at transition Reynolds numbers

Abstract: Sting-free aerodynamic drag measurement on ellipsoidal cylinders in subsonic wind tunnel at transition Reynolds numbers

Lift and drag of a wing-cone configuration in hypersonic flow

Abstract: R a great interest has arisen in the study of hypersonic flight, in connection with high-speed transportation and re-entry vehicles. Requirements of maneuverability and long range flight impose the choice of vehicles with a relatively large lift-drag ratio. In order to gain information on the possible characteristics of such vehicles, a considerable effort is devoted to the study of bodies of simple shapes. A body which can give good lift and drag characteristics is a cone-wing configuration (Fig. 1); with this configuration an attempt is made to take advantage of the aerodynamic interference between the cone and the wing, which gives rise to a rather large increase in pressure on the windward side of the body, and a corresponding decrease on the leeward side. The present Note gives some results of a series of experiments performed to determine the pressure distribution and the total forces on a configuration consisting of a 20° cone with wings located at 60° from the plane of symmetry and sweepback angle of 75°. The Mach number of the experiments was equal to 5.8; in these conditions the leading edge of the wing was subsonic. The lift and drag coefficients have been determined from the pressure distribution and directly from balance measurements. The results are compared to those obtained with an isolated cone.

Drag of a Supercritical Body of Revolution in Free Flight at Transonic Speeds and Comparison with Wind Tunnel Data

Abstract: The forebody drag of a supercritical body of revolution was measured in free flight over a Mach number range of 0.85 to 1.05 and a Reynolds number range of 11.5 x 10 to the 6th power to 19.4 x 10 to the 6th power and was compared with wind-tunnel data. The forebody drag coefficient for a Mach number less than 0.96 was 0.111 compared with the wind-tunnel value of 0.103. A gradual increase in the drag occurred in the Langley 8-foot transonic pressure tunnel at a lower Mach number than in the Langley 16-foot transonic tunnel or in the free-flight test. The sharp drag rise occurred near Mach 0.98 in free flight whereas the rise occurred near Mach 0.99 in the Langley 16-foot transonic tunnel. The sharp rise was not as pronounced in the Langley 8-foot transonic pressure tunnel and was probably affected by tunnel-wall-interference effects. The increase occurred more slowly and at a higher Mach number. These results indicate that the drag measurements made in the wind tunnels near Mach 1 were significantly affected by the relative size of the model and the wind tunnel.

A comparison of the lift of flat delta wings and waveriders at high angles of incidence and high mach number

Abstract: It has been suggested that in the conditions of lifting re-entry caret wings are likely to have higher lift coefficients than flat-bottomed wings with the same ratio of lift to drag. Thus, for given speed and wing loading, they can re-enter at higher altitudes with a consequent reduction in stagnation point heating rate. In this paper thin-shock-layer theory is used to study the lifting properties of caret and flat-bottomed wings and of wings with concave lower surfaces. It is found that significant gains in lift coefficient can be achieved with moderately recessed lower surfaces. These results hold for both perfect and real gas flows.

Drag coefficients for partially inflated flat circular parachutes

Abstract: Free-body tests of flat circular parachutes and determination of aerodynamic drag coefficients during partial inflation

Longitudinal Static Stability and Drag Characteristics of A-7D and F-4E Aircraft with Various External Store Configurations at Transonic Speeds

Abstract: : Longitudinal aerodynamic characteristics of 0.05-scale models of A-7D and F-4E aircraft were obtained at Mach numbers from 0.50 to 1.30 to determine the effects of store configuration and location on stability and drag. Prototypes, as well as a family of proposed store configurations, were tested.

Computer programs for calculation of aerodynamic interference between lifting surfaces and lift and cruise fans

Abstract: Users manual for 3 computer programs for predicting aerodynamic interference between lifting surfaces and lift and cruise fans in transport-type aircraft

Longitudinal Static Stability and Drag Characteristics of F-4D Aircraft with Various External Store Configurations at Transonic Speeds

Abstract: : Force and moment data were obtained with a 005-scale model of the F- 4D aircraft at Mach numbers from 075 to l30 to determine the effects of different store and rack configurations on the static stability and drag of the aircraft Six proposed rack launchers and four proposed store shapes were tested for a total of 57 external loading configurations