Showing papers on "Leading edge published in 1968"

Analysis and design of wing-body combinations at subsonic and supersonic speeds.

Abstract: The method of aerodynamic influence coefficients has proved to be an effective tool for the analysis and design of wings, bodies, and wing-body combinations at supersonic speeds. This paper describes the extension of this method into the subsonic flow regime, and correlates the theory with experiment over a wide speed range. The method may be applied to the calculation of the pressures and forces acting on arbitrary wing-body combinations in steady flight, including aeroelastic effects, and to the design of wing camber surfaces in the presence of a body. Nomenclature A = aspect ratio b = span c =. chord C = aerodynamic coefficient d = distance / = singularity distribution function F = distribution function K = constant I = body length L — panel sweep M = Mach number r = radius Re = real part u, v, w = perturbation velocities U = freestream velocity x, y, z = Cartesian coordinates a. = angle of attack 0 = angular coordinate, panel inclination X = taper ratio A = leading edge sweep £, rj = integration variables

Aerodynamic loading on a two-dimensional airfoil during dynamic stall.

Abstract: A general theory is developed for the unsteady aerodynamic loading on an airfoil during dynamic stall. The dynamic stall process is represented by the shedding of vorticity from the vicinity of the airfoil leading edge. The theory is subsequently applied to the prediction of the stall-induced airloading on an airfoil experiencing a sudden onset of flow and on an airfoil performing oscillatory pitching motion. Satisfactory agreement between theoretical and experimental pressure distributions, forces and moments, and vortex trajectories is demonstrated.

Improved calculations of leading-edge separation from slender, thin, delta wings

Abstract: In previous calculations (Mangler & Smith 1959) of the vortex-sheet model of leading-edge separation, only qualitative agreement was found with experimental observations. Because the numerical treatment of the model was then necessarily incomplete, it was uncertain how far the lack of quantitative agreement was to be attributed to the limitations of the model. The use of an automatic digital computer has now made it possible to reduce the uncertainties in the calculation to a negligible level. The features of interest in the real flow are more accurately predicted and the remaining discrepancies can be ascribed to the deficiencies in the model. The paper describes the method used to locate the vortex sheet and determine its strength in terms of the two boundary conditions on it; assesses the credibility of the results; and relates them to the observations. It is concluded that the model successfully predicts the observed height of the vortex above the wing, though the predicted lateral position is in error by up to 6% of the semi-span of the wing. This error falls as the incidence increases and is less when transition occurs in the boundary-layer upstream of secondary separation. Normal force is predicted accurately as is the distribution of pressure on the lower surface and the inboard part of the upper surface. The observed suction peak below the vortex changes its character when transition occurs in the boundary-layer upstream of secondary separation. The model predicts the suction peak in the turbulent case fairly well, but it is clear that detailed prediction of the suction peak is not possible by a model which is wholly inviscid.

Hypersonic viscous flow over slender bodies with sharp leading edges.

Abstract: : The hypersonic viscous pressure interaction is treated by the development of a set of equations valid throughout the boundary layer, shock-wave structure and inviscid core. Primary interest is concerned with the nature of the leading edge continuum merged layer in which the shock wave and boundary layer are indistinguishable. Due to the parabolic nature of the equations, finite-difference solutions are attainable. The flow over a flat plate at zero incidence, as well as angle of attack, was considered. Velocity and state variable distributions across the viscous layer depict the formation of an outer shock wave and inner constant pressure boundary layer. The calculated values of surface pressure, heat transfer and shock jump conditions were at first significantly below the values predicted by strong interaction theory. Agreement was quite good downstream of the merged layer where Rankine-Hugoniot jump conditions were satisfied to within 8%. (Author)

Application of the leading-edge-suction analogy of vortex lift to the drag due to lift of sharp-edge delta wings

Abstract: Sharp edge delta wing drag prediction by application of leading edge suction analogy of vortex lift

Methods and high lift systems for making an aircraft wing more efficient for takeoffs and landings

Abstract: A highly efficient aircraft wing is formed by drooping the leading edge portion and extending a leading edge flap for transforming the wing into the most efficient condition for takeoff, and by drooping the leading edge portion and extending a multiplicity of leading edge flaps for transforming the wing into the most efficient condition for landing. Another method comprises extending a leading edge flap from retracted position in the leading edge portion of a wing for transforming the wing into the most efficient condition for takeoff, and extending three leading edge flaps from retracted position in the wing leading edge portion for transforming the wing into the most efficient condition for landing. At least two high lift systems for carrying out the above methods comprise mounting in the wing leading edge portion three interconnected, end-to-end, fore-and-aft, leading edge flaps and two different linkages for folding the three flaps internally of the leading edge portion operable by single and double actuators respectively.

Variable area cooled airfoil construction for gas turbines

Abstract: A cooled airfoil for gas turbines having a hollow airfoil-shaped body with an impingement tube disposed therein in spaced relation to the sidewalls. Such tube receives a cooling medium and is formed with openings disposed to direct the cooling medium against the inner surface of the leading edge wall. The inner surfaces of the body sidewalls have heat dissipating fins substantially engaging the impingement tube to provide passages extending chordwise of the airfoil to conduct the cooling medium to the rear where it is vented through openings in the airfoil trailing edge. The passage forming fins may be variably spaced and of variable height to vary the cooling medium flow area at predetermined variable height to vary the cooling medium flow area at predetermined regions of the airfoil sidewalls, and other fins of predetermined variable height may be provided in the passages to effect differential cooling effects as required by the temperatures to which different portions of the airfoil are exposed.

Microelectrode Study of Delayed Conduction in the Canine Right Bundle Branch

Abstract: The electrophysiology of conduction delay was investigated in the semi-isolated right bundle branch of 30 large mongrel dogs. Delay was produced by the external application of an electric blocking current to the bundle branch. Multiple recordings with glass capillary microelectrodes revealed two basic deflections associated with the delay phenomenon. An initial, or leading, deflection originated from the proximal or leading edge of the block and was rapidly transmitted through the block with progressive decay of voltage and rise velocity. A second, or trailing, deflection originated from the regenerative response at the distal or trailing edge of the block and was rapidly transmitted retrograde into the block, with progressive decay of voltage and rise velocity. The transmitted potentials appeared to be electrotonic in nature. The leading deflection appeared to be the transmitted event which maintained a conduction ratio of 1:1 through the block. The magnitude of delay was then related to the time required for this deflection to reach the threshold potential and initiate a regenerative response in the trailing portion of the block where the cells were less affected by the blocking current.

Corner edge connector for printed circuit boards

Abstract: Disclosed is an L-shaped edge connector for the use with circuit modules such as printed circuit boards. The inner L-shaped surface of the connector is formed with a slotted channel adapted to receive the leading edge of the board in its base portion. The base of the connector is further fitted with spring contacts for securing and making electrical contact with the leading edge of the board. The slotted channel within the upright portion of the connector is adapted to receive an adjacent edge of the board and provide lateral support thereto.

Pressure-loading functions for oscillating wings with control surfaces.

Abstract: In the linearized formulation of the oscillating-surf ace problem, singularities in the lift distribution occur at subsonic leading edges, at control surface leading edges, and in general wherever the up wash prescribed by the wing deformations is discontinuous. These singularities are examined by use of the method of matched asymptotic expansions. It is shown that for a known discontinuity in upwash (as in the case of the control surface) the form, as well as the strength, of the singularity are determined uniquely. For subsonic leading edges only the form, but not the strength, of the singularity can be determined. A discussion is also given of the proper shape of the loading functions near side edges. Nomenclature b = reference length (root semi chord) Cp = pressure coefficient k = reduced frequency, ub/Um M = Mach number of freestream MN = M cos A, Mach number normal to edge p — pressure amplitude, Cp = peikt t = time Um = freestream velocity w = amplitude of prescribed upwash on the wing X) y} z = Cartesian coordinates with x in the freestream and in the span wise direction xc = location of control-surfa ce leading edge and hinge Xj y, z = stretched variables

Saw guided splitter

Abstract: In combination with a saw machine having a relatively thin circular saw mounted upon an arbor with floating axial looseness and a saw guide defining a limiting control plane for guiding the leading edge of said saw, a splitter mounted for lateral movement and laterally positioned by the rear edge of said saw. A splitter for use in saw machines having a circular saw and comprising a pair of spaced contacts, each contact having a bearing surface for making contact with opposite sides of a circular saw, and a divider member having a plurality of resilient contacts that extend into a region above said spaced contacts and in trailing relation to the rear edge of a saw.

Straight feed press

Abstract: A sheet-fed lithographic offset printing press in which sheets are aerodynamically supported and directed in a single horizontal plane straight to and through individually driven and mechanically synchronized multi-color perfecting towers while the sheet is continuously gripped and moved by a single set of grippers at the leading edge so that only blanket printing cylinders touch the sheet, eliminating sheet transfer between the time the sheet leaves the feeder and the time it reaches the delivery.

The transverse curvature effect on the incompressible laminar boundary layer for longitudinal flow over a cylinder

Abstract: A solution to the partial differential equations governing incompressible laminar flow in the axial direction over a circular cylinder is presented. A method is employed which reduces the partial differential equations to a set of ordinary differential equations which are then solved consecutively. The solution is initiated at a leading edge and proceeds far downstream. Velocity profiles and values for the coefficient of skin friction, displacement thickness and momentum thickness are obtained. The results are compared to previously obtained solutions valid near the leading edge and asymptotic solutions valid far downstream.

Integrator-schmitt trigger circuit

Abstract: A transistorized integrator-Schmitt trigger circuit for delaying the leading edge of an input pulse for a first predetermined time duration and for delaying the trailing edge of the input pulse for a second predetermined time duration. An input transistor is rendered conducting on the leading edge of an input pulse whereby current flows through the transistor to charge a capacitor included in an integrator circuit connected to the input transistor. The charging rate of the capacitor is adjusted such that the upper threshold level of a conventional Schmitt trigger circuit connected to the capacitor is achieved at a first predetermined time duration after the occurrence of the leading edge of the input pulse. As a result, a transition in the output level of the Schmitt trigger circuit occurs at the first predetermined time duration after the leading edge of the input pulse. On the trailing edge of the input pulse, the input transistor is rendered nonconducting and the capacitor discharges. The discharge rate of the capacitor is adjusted such that the lower threshold level of the Schmitt trigger circuit is achieved at a second predetermined time duration after the occurrence of the trailing edge of the input pulse. As a result, the output of the Schmitt trigger circuit returns to its original level at the second predetermined time duration after the trailing edge of the input pulse. A charge reduction circuit is also provided for reducing the charge in the capacitor to zero after the output of the Schmitt trigger circuit has returned to its original level thereby increasing the duty cycle of the integrator-Schmitt trigger circuit.

Method of fabricating a turbine blade having a leading edge formed of weld metal

Abstract: THE PRODUCTION OF TURBINE BLADES IN WHICH A BLADE BLANK IS PROVIDED IN THE AREA OF THE INLET EDGE WITH A STEEL WELD PORTION, WHICH, AFTER SMOOTHING OF ANY UNEVEN SPOTS, IS SHAPED TOGETHER WITH THE BLADE BODY TO THE FINAL DIMENSIONS IN A DROP FORGE AND FINALLY SUBJECTED TO HEAT TREATMENT.

Flat magnetic heads

Abstract: This invention is directed to a magnetic transducing head for use with a moving magnetic recording medium. Specifically, the invention is directed to a physical construction for the magnetic transducing head for providing an improved contact between the magnetic medium and the magnetic transducing head wherein the magnetic transducing head includes a sharp leading edge constructed of wear-resistant material and wherein the leading edge forms an included angle of 90* or greater between the magnetic medium and the leading edge so that as the magnetic medium passes over the sharp leading edge, the leading edge removes air from the surface of the magnetic medium, which removal of air produces a pressure differential in a direction to urge the magnetic medium into contact with the face of the magnetic transducing head. Generally, the invention may also provide for a flat face for the magnetic transducing head so as to maintain the close contact between the magnetic medium and the face of the magnetic transducing head.

Angle of attack and leading edge effects on the flow about a flat plate at Mach number 18.

Abstract: Data concerning viscosity and bluntness-induced pressures on a flat plate at angle of attack are presented for the strong interaction regime. Values of the hypersonic viscous interaction parameter x vary between 25 and 50. Pitot probe surveys have been made to determine the shock-wave location. Both positive and negative angles of attack were considered and incidence was varied from — 6° to 9°. Leading edge Reynolds number extends over the range from 70 to 1500. The flat plate is water cooled and the corresponding ratio of wall-to-stagnation temperature is about 0.21. Results are compared with existing theoretical models.

Experimental investigation of the ventilation of vertical surface-piercing struts in the presence of cavitation

Abstract: : An experimental program was conducted in the Lockheed underwater missile facility to determine the mechanism, characteristics, and the significant parameters controlling ventilation in the presence of cavitation for three streamlined, vertically, surface-piercing strut models Tests were performed for speeds from 20 to 30 fps, for yaw angles from 6 to 10 degrees, for submergences of 1 to 15 chord lengths The radius of the leading edge of the struts ranged from 0 to 00327 chord lengths Forces were measured and flow photographs were obtained The importance of vapor cavitation number as the principal parameter influencing the inception of ventilation was demonstrated

Transpiration cooling in a laminar boundary layer with solid wall upstream effects.

Abstract: An analytical model is developed that considers the effect of a run of boundary-layer growth preceding a transpiration surface. The model consists of a laminar, incompressible boundary layer on a flat plate. The solution considers the classical Blasius solution to generate the initial conditions over the solid portion of the boundary layer and is extended into the transpiration region by applying a finite difference technique. It was found that the solid leading edge had a significant effect on the magnitude of the skin-friction coefficient over the transpiration surface. It is clear that further investigations are required for transpiration systems preceded by a run of boundary-layer growth over a solid leading edge.

Mechanism for successively delivering sheet articles from a stack thereof to a folding machine

Abstract: Bottom delivery feeders are employed in conjunction with a newspaper folding and wrapping machine and serve to sequentially feed sections of a newspaper into the machine for collation with the main body of the newspaper. One, two or three of such feeders of varying design may be used with the folding and wrapping machine in various operational configurations, depending upon the nature of the sections to be collated with the main newspaper. One feeder embodiment is particularly adapted to feed multileaved newspaper sections from a stack thereof. A hopper receives the stack of newspaper sections, a shelf beneath the stack being utilized to support the trailing edge portion of the lowermost section. A pair of stationary fingers supports the leading edge portion and feeding is effected from the bottom of the stack by a plurality of oscillatory grippers which frictionally engage the lowermost section and withdraw the leading edge portion thereof from between the next to the lowermost section and the support fingers. The trailing edge portion of the lowermost section is then withdrawn by pinch rollers which receive the leading edge portion upon return movement of the grippers as the same are continuously oscillated to provide sequential feeding. In a modified form of this embodiment, a single, reciprocable support finger is employed and is particularly adapted for use in the feeding of thin supplements with a hard edge at the fold only. A second feeder embodiment is particularly suited for the feeding of tabloid size sheets which require folding prior to collation with the main newspaper. The same basic operational principles are employed in the withdrawal of the leading edge portion of the lowermost sheet from the hopper. However, continuously rotating grippers are used in conjunction with a roller against which force is applied by the grippers to pinch the loop (formed upon withdrawal of the leading edge portion) between the grippers and the roller to guide the same into a delivery conveyor that transports the withdrawn sheet in folded form to the folding and wrapping machine. The feeders of the first and second embodiments may both be mounted on the machine and used singly depending upon the nature of the paper to be fed. When the feeder of the first embodiment is in operation, the sections being fed therefrom are conveyed through the other feeder, the operating components of the latter being adapted to assist in the conveying of the sections to the folding and wrapping machine. When it is desired to employ such other feeder to feed tabloid sheets to the machine, it operates in the normal manner and the first feeder is inoperative at this time. A top delivery feeder for sequentially delivering wrappers to the folding and wrapping machine operates in conjunction with either of the above feeders and employs a plurality of rotary grippers which are brought into frictional engagement with the uppermost wrapper of a stack thereof during each revolution of the grippers. The grippers are driven by a common shaft but are coupled with the shaft in a manner to permit the grippers to rotate ahead of the shaft free of the latter as each wrapper is advanced from beneath the grippers by a conveyor that receives the leading edge of each wrapper as it is fed from the stack.

Means for reducing air pressure against leading edge portions of airplane wings and ailerons

Abstract: This disclosure relates to means for reducing the back pressure of a fluid against a vehicle moving in, on or through said fluid. It can be applied to both air- and waterborne vehicles. When applied to waterborne ships and the like it reduces back pressure and friction of the water against their prow portions. When applied to air vehicles which travel at supersonic speeds it reduces air pressure and air friction against the leading edges of wings, ailerons, nose cones and the like and helps to prevent overheating and sonic boom.

Airfoil bridle apparatus

Abstract: The present invention relates to a bridle assembly for use with a semirigid airfoil supported by an aircraft fuselage. The airfoil includes a spar defining a rigid leading edge, a cable defining a trailing edge, and flexible material interconnecting the spar and cable and defining a spanwise camber distribution. The bridle assembly includes at least one bridle cable secured to the airfoil trailing edge cable, with the assembly being secured in tension to the fuselage, to create tension in the airfoil flexible material and retard changes in its camber distribution.

Hybrid circuit breaker having means for detecting the leading edge of the arc voltage at the contacts thereof

Abstract: A hybrid circuit breaker comprising a pair of contacts actuated by an electromagnet, a thyristor for shunting the contacts, an extinction condenser for the shunt thyristor, an extinction thyristor adapted to control the discharge of the condenser, and a circuit for controlling the firing of the thyristors comprising a circuit for differentiating the leading edge of the arc voltage across the contacts and a monostable multivibrator responsive to the leading edge of said arc voltage for generating an impulse for firing the shunt thyristor. D R A W I N G

On the Calculation of Unsteady Nonlinear Three-Dimensional Supersonic Flow Past Wings

Abstract: A comprehensive study is made of factors influencing the accuracy of predicted thickness effects on the flow due to oscillatory motion of a sweptback wing in supersonic flight. For a delta planform with its leading edge swept at or near the Mach angle, the streamlines and velocity pattern due to thickness are found to be highly three-dimensional. Based on this observation, improvements are suggested to previous approximate second-order theories for the unsteady loading. Numerical examples are presented for a 45 deg della which indicate a substantial difference between the linearized and nonlinear pressure distributions. Although a greater volume of computation is needed to guarantee adequate accuracy, practical means are described for the complete numerical solution of problems of this type.