Showing papers on "Leading edge published in 1981"

A coolable airfoil for a rotary machine

Abstract: A coolable airfoil 16 for a rotary machine is disclosed. The coolable airfoil includes a plurality of cooling passages 56, 86, 88 and 114 extending in the spanwise direction. A plurality of turning passages such as the turning passage 82 and the turning passage 90 turn the flow between the spanwisely extending passages. A vane 92 in the turning passage 90 is spaced from a spanwisely extending baffle 48 to form a sub-passage 94 therebetween upstream of a corner region 90c. A trip strip 96 extends between the vane and the wall and is angled with respect to the approaching flow. A similar construction is found in the turning passage 82. In one particular embodiment, the turbine blade includes a spanwisely extending leading edge passage connected to the trailing edge region by a chord-wisely extending tip passage 58.

Coolable airfoil for a rotary machine

Abstract: A coolable airfoil 10 for rotary machines is disclosed. The airfoil has a passage 54 extending spanwisely through the leading edge region 26 of the blade. The first passage has a plurality of trip strips 66s, 66p canted toward the approaching flow and angled with respect to the wall in the leading edge region to turbulently increase the amount of cooling flowed to the forward most portion of the passage in the leading edge region. In one embodiment, a hole 72 in fluid communication with a turning passage 64 in the tip region of the blade downstream of the first passage is in fluid communication with the trailing edge of the blade.

Visualization of Transition in the Flow over an Airfoil Using the Smoke-Wire Technique

Abstract: The smoke-wire technique was used for visualization of the transition of the free shear layer associated with the laminar separation bubble of a NACA 663-018 airfoil section at low Reynolds number (Rec = 50,000120,000). The smoke-wire technique allows for the introduction of fine smoke streaklines into the flowfield through the electrical resistive heating of a very fine wire which has been coated with oil and which is located upstream from the leading edge of the airfoil section. Streakline data were collected using both high speed still and motion picture photography.

On boundary layers in fluid mechanics that decay algebraically along stretches of wall that are not vanishingly small

Abstract: It is shown that certain "backward" boundary layers exist which exhibit an algebraic behaviour near the outer edge, but which still predict the correct wall conditions along an extended part of the boundary. This seems to be in contradiction with common knowledge which has it that such boundary-layer solutions can apply only at singular points in the flow field. However, the paper shows that the very same methods that prove the limited applicability of "algebraic" boundary layers in forward flows (flows with a definite leading edge) can be used to ascertain the extended applicability of such solutions in "backward" flows (when the leading edge recedes to stations infinitely far upstream).

The influence of mean shear on unsteady aperture flow, with application to acoustical diffraction and self-sustained cavity oscillations

Abstract: This paper discusses the linearized theory of unsteady flow through a two-dimensional aperture in a thin plate in the presence of a grazing mean flow on one side of the plate. The mean shear layer is modelled by a vortex sheet, and it is predicted that at low mean-flow Mach numbers there is a transfer of energy from the mean flow to the disturbed motion of the vortex sheet provided (i) the Kutta condition is imposed at the leading edge of the aperture, resulting in the unsteady shedding of vorticity from the edge, and (ii) the width of the aperture 2s satisfies ½ < 2s/λ < 1.1, where λ is the hydrodynamic wavelength of the disturbance on the vortex sheet within the aperture. The theory is used to examine the effect of mean shear on the diffraction of sound by a perforated screen, and to predict the spontaneous excitation and suppression of self-sustained oscillations in a wall-cavity beneath a nominally steady mean flow. In the latter case support for the proposed theory is provided by a favourable comparison of theoretical results with experimental data available in the literature.

Leading edge vortex flap for wings

Abstract: A series of flaps (21) along the leading edge of a highly swept-back wing (20) for a supersonic airplane; wherein, the spanwise series of the flaps (21) comprise a double-flap chordwise having fore and aft flap segments (22, 24). When the leading edge double-flap is positioned at a forward and downward angle-of-deflection relative to the wing (20), the fore-flap segment (22) is further positioned at an angle-of-deflection relative to the aft-flap segment (24). This difference in the deflection angles, between the fore-flap segment (22) and the aft-flap segment (24), creates a vortex flow region ahead of the wing leading edge; and this vortex functions to control separation of an upper surface boundary layer airflow, over the remainder of the upper surface of the wing (20). Also, the vortex flow will move in a spanwise direction outboard toward the tip of a swept-back wing (20), while remaining forward or ahead of the upper surface of the aft-flap segment (24). Additional embodiments relate to various other arrangements for creating a leading edge vortex flow to maintain attached flow over the remainder of the upper surface of the wing.

Variable camber leading edge mechanism with Krueger flap

Abstract: An actuating mechanism for variable camber leading edges of aerodynamic airfoils characterized by its rigidity and structural stability and which permits varying the camber of a flexible continuous airfoil skin through leading edge deflection angles ranging from on the order of 14° to on the order of 22° with reference to the wing box chord line without deployment of a Krueger flap and up to on the order of 32° with deployment of a Krueger flap; and, which permits varying the camber of a flexible continuous airfoil skin while maintaining a uniform, essentially constant curvature throughout the chordal extend of deflection for any given degree of deflection; yet, wherein: (a) the upper continuous flexible airfoil skin (i) is not required to provide load bearing support, (ii) is not subjected to chord-wise stress from movement of the actuating linkage, and (iii) is not subjected to localized stress resulting from non-uniform deflection; (b) the actuating linkage is contained entirely within the airfoil aerodynamic contour or airfoil envelope at all operating positions; (c) the actuating linkage may be readily employed with a wide range of conventional structural wing box configurations; and (d), which permits of deployment of either " slotted" Krueger flaps to meet operating requirements during take-off and landing operations or to function as an inflight speedbrake under both high speed and low speed flight conditions More specifically, the variable camber leading edge actuating mechanism comprises a simple 4-bar linkage arrangement which readily permits of incorporation of Krueger flaps actuated by a suitable torque tube extending span-wise through the deflectable leading edge of the airfoil

Vortex-Lattice Method for the Calculation of the Nonsteady Separated Flow over Delta Wings

Abstract: An analysis is made of the wake structure and the forces on a delta wing as it undergoes nonsteady motion, wherein the flow separates at the leading edge. Comparisons of these predictions with existing experimental and theoretical data for the nonsteady linear and nonlinear motions indicate good agreement. It was found that the time-dependent, wake-shedding numerical procedure applied here for the wake rollup and the lift force calculation resulted in considerable saving of computer time over methods using the iterative wake rollup procedure. Calculated results for various motions of the delta wing, including the plunging motion, are presented for both the separated and the attached flow cases.

Coolable airfoil for a rotary machine

Abstract: A coolable airfoil 10 for rotary machines is disclosed. The airfoil has a passage 54 extending spanwisely through the leading edge region 26 of the blade. The passage has a plurality of trip strips 68 canted toward the direction flow. Each trip strip includes a vortex generator integrally formed with the trip strip which is spaced from the wall of the airfoil. In one embodiment, a plurality of trip strips each having an integral vortex generator are disposed in the passageway and at least one of the vortex generators is of greater height than the remaining vortex generators.

Extendible airfoil track assembly

Abstract: An actuation and extension mechanism for aerodynamic high-lift devices such as a wing leading edge slat or a wing trailing edge flap; wherein an aerodynamic panel (20) is connected to one end of an extendible track member (23) that is supported and guided by its other end through rollers (26) fixedly mounted to wing rib structure (15). The track member incorporates a separate rack gear segment (24) internally thereof as part of the extension or retraction mechanism and this combination of track and gear segment provides the primary support and drive means to the high-lift device. without compromising the structural strength, safety, or operational reliability of said combination.

Moving surface boundary layer control for aircraft operation at high incidence

Abstract: The paper studies effectiveness of the moving-surface boundary-layer control on a NACA 63-218 (modified) two-dimensional wing used in the Canadair CL-84, a twin-propeller V/STOL design. Tests with rotating cylinder(s) at the leading edge of the airfoil and/or of the flap show the former to have a significant effect on the maximum lift, stall characteristics, and lift/drag ratio. On the other hand, the advantage gained by the presence of the rear cylinder is relatively small for the slotted flap configuration. The availability of a high value of lift suggests the approach velocity with this form of boundary-layer control is likely to be limited only by the lateraldirectional stability characteristics. The concept presents several possible applications including a mechanism for delaying the vortex-induced resonance of bluff bodies.

Mounting apparatus for rear-view mirrors and the like

Abstract: A rear-view mirror mounting apparatus for attaching a rear-view mirror to a windshield includes a substantially flat, receiving member and a hollow, inserting member which is slidably received within the receiving member. The receiving member includes a tapered, dovetail-like receiving channel which is symmetrical about the longitudinal centerline of the receiving member. The inserting member is contoured at one end with a spherical element suitable for receipt by a pivot mechanism or similar interconnection means and the opposite end is contoured with a flared, conical shape. The bottom edge of this flared, conical shape includes a leading edge portion, a trailing edge portion and two side edge portions. The two side edge portions are disposed in a first plane and the leading and trailing edge portions are disposed in a second geometric plane parallel to the first, the two side portions are suitably sized and spaced so as to fit beneath the undercut side edges of the receiving channel. Thus, as this inserting member is advanced downwardly in the direction of narrowing taper, the two side edge portions as well as the leading and trailing edge portions make contact with the receiving member at four primary points of contact interference which are approximately 90 degrees apart.

Utilization of wind energy

Abstract: A wind energy device comprising a first airfoil having a leading edge, a trailing edge and a tip, means supporting the airfoil above a surface, the airfoil being adapted, when traversed by a prevailing wind, to generate a vortex at its tip, an air deflector associated with the airfoil and arranged so as to deflect prevailing wind traversing the deflector into the vortex to augment the energy of the vortex, means to vary the orientation of the airfoil relative to the prevailing wind, and a rotary device located in the path of the vortex and adapted to be driven by the wind in the vortex.

Cooled turbine blades

Abstract: 1. Improvement in cooled turbine blades, comprising two cavities separated over the height of the blade by an internal partition each supplied at the lower part with a flow of cooling fluid of which an uspstream cavity with radial flow and a downstream cavity divided into two radial tangential flow zones in the direction of the trailing edge, characterized in this that the upstream cavity (1) has ribs (11) facilitating heat exchange and holes formed in the leading edge and the downstream cavity (2) comprises, in the central zone for the radial flow of fluid, bridge members (12) of large section, whilst in the trailing edge zone (3) with tangential flow towards the trailing edge, the said downstream cavity comprises bridges (13) of small section completed by deflecting members (14) guiding the radial flow, tangentially towards the orifices at the trailing edge (3), and in this that a part of fluid flows is exhausted through outlet orifices provided at the upper part of each cavity.

Aircraft wing provided with a high-lift system in its leading edge

Abstract: The invention relates to aircraft wings, wherein the fairing element between the leading edge of a wing and the fuselage comprises a streamlining flap movable between a folded position in which it is housed in a recess in the fairing element and forms a part of the leading edge and the part adjacent the lower surface of said fairing element, and an extended position in which it ensures continuity of the leading edge between the fuselage and the high-lift spoiler likewise in extended position. Moreover, there is a communication between the housing of the streamlining flap and the housing of the high-lift spoiler so that, when these two flap elements are in their extended positions, the air penetrating in the housing of the streamlining flap disposed on the lower surface side emerges through the housing of the high-lift spoiler disposed on the upper surface side, with the result that there is an increased upper surface blowing.

Boundary-Layer Control on Wings Using Sound and Leading-Edge Serrations

Abstract: T study systematically examined the effect of leadingedge serrations, sound emitted from periodically spaced holes near the wing leading edge, and external sound upon the flow over two low-speed wings, one with camber (NACA 2412) and one without (NACA 0015). The main purpose of the study was to determine whether these techniques could be used to increase the lift coefficient of these wings. These techniques were all found to have a beneficial effect upon the aerodynamic properties of these airfoils. The first two techniques could be practically used to improve the low-speed lift and stall performance of light aircraft during takeoff and landing and could be used for stall/flutter suppression on rotor and propeller blades.

Analytical Prediction of Vortex Lift

Abstract: General integral expressions are derived for the nonlinear lift and pitching moment of arbitrary wing planforms in subsonic flow The analysis uses the suction analogy and an assumed pressure distribution based on classical linear theory results The potential flow lift constant and certain wing geometric parameters are the only unknowns in the integral expressions Results of the analysis are compared with experimental data and other numerical methods for several representative wings, including ogee and double-delta planforms The present method is shown to be as accurate as other numerical schemes for predicting total lift, induced drag, and pitching moment b c c CL CD Cm CT Cs cc, ccd E2 Nomenclature = aspect ratio = wing span =chord = reference length = lift coefficient = drag coefficient = pitching moment coefficient = thrust coefficient = suction coefficient = section lift coefficient = section induced drag coefficient = section suction coefficient = pressure loading coefficient = drag = proportionality constant, Eq (32) = proportionality constant, Eq (53) = chordwise function, Eq (44) ff(rj) = span wise f unction, Eq (28) K = potential constant L =lift loading constant, Eq (5) S = suction force SR = reference area s = suction force per unit length T = leading edge thrust, Eq (7) T' = leading edge thrust per unit length V = freestream speed Wj = downwash velocity component, Eq (11) a = angle of attack F = vorticity p = freestream density £ = nondimensional chordwise coordinate 77 = nondimensional spanwise coordinate A = leading edge sweep angle Subscripts P = potential flow E =edge / = induced VLE = leading edge vortex VSE = side edge vortex

Closed-Form Solutions for Finite Length Crack Moving in a Strip Under Anti-Plane Shear Stress

Abstract: In this paper exact expressions for the anti-plane dynamic stress distributions around finite length cracks propagating with constant velocity in infinitely long finite width strips are determined. Two cases of practical importance are investigated. Firstly, the lateral boundaries of the strip are clamped and displaced in equal and opposite directions, to produce anti-plane shear resulting in a tearing motion along the leading edge of the crack and, secondly, the lateral boundaries of the strip are subjected to shearing stresses. Employing Fourier transforms the solution of each problem is reduced to solving a pair of dual integral equations. Closed-form solutions of these integral equations are obtained leading to exact expressions for the stress intensity factors. Numerical results are presented in graphical form.

Deformation and secondary faulting near the leading edge of a thrust fault

Abstract: Summary Elastic dislocation models are used to calculate the displacements of the ground surface produced by a thrust fault climbing section. The models show that the surface uplift is asymmetrical with the steepest slope above and ahead of the fault. The gradient of the surface uplift becomes steeper and the magnitude of the uplift increases as: (1) the fault dip increases; (2) the fault becomes shallower; and (3) the shear modulus of the material above the fault decreases relative to the shear modulus of the material containing the fault. Elastic dislocation, photoelastic, and clay models are used to predict the orientation of secondary faults which might be produced by a thrust fault climbing section. In general, the secondary faults strike parallel to the master fault, but the dislocation models show that there are regions in both the hanging and foot walls where the secondary fault strikes are not parallel to the master fault. The models suggest that a thrust fault in a homogeneous medium is likely to extend itself with about the same dip, while a thrust fault moving from a stronger material into a weaker material is likely to flatten and become layer-parallel. High-angle antithetic faults or back thrusts in the hanging wall are associated with a thrust fault propagating through a homogeneous medium, but layer-parallel antithetic faults are more likely than high-angle antithetic faults in the hanging-wall when a thrust fault is propagating from a stronger to a weaker medium.

Design, Analysis, and Tests of a Shuttle-Type Heat-Pipe-Cooled Leading Edge

Abstract: A one-half-scale heat-pipe-cooled leading edge model was designed and fabricated to verify feasibility and performance of a full-scale Shuttle-type orbiter design. Model performance was investigated experimentally by radiant heating and aerothermal tests and analytically by using a simple technique which predicts heat pipe startup from the frozen state and also predicts transient and steady-state thermal behavior. Analytical results agree well with experimental results for startup and steady-state heat pipe operation. The results indicate that variations in angle of attack and roll orientation had a negligible effect on heat pipe performance. The heat pipes effectively isothermalized the leading edge, and reduced peak temperatures to levels compatible with the use temperatures of superalloys. Results of these tests demonstrated the durability of the heat-pipe-cooled leading edge in withstanding Earth-entry thermal and mechanical loads and indicate that the use of heat pipes in leading edge structures is a reliable concept for fully reusable hypersonic cruise and space transportation systems.

Low-Speed Aerodynamic Characteristics of a Small, Fixed-Trailing-Edge Circulation Control Wing Configuration Fitted to a Supercritical Airfoil

Abstract: : Excellent high-lift and cruise performance of a small, round, fixed circulation control wing (CCW) trailing edge fitted to a supercritical airfoil has been confirmed by subsonic wind tunnel investigations. This fixed-trailing- edge blown high-lift airfoil generates a negligible subsonic cruise drag penalty, but can generate a section lift coefficient near 7.0. This configuration is a significant improvement over the flight-proven A-6/CCW airfoil that had similar lift performance, but had a large trailing edge requiring mechanization for transition to cruise flight. Further, the large leading edge radius of the supercritical airfoil allows operating at high lift over a moderate angle-of-attack range. These results imply the feasibility of a mono-element airfoil with no moving components required for high lift; the transition from the cruise to the high-lift configuration is accomplished by blowing from a fixed slot. The favorable characteristics of both the cruise and high-lift airfoils are retained without compromise to either. (Author)

The Role of Displacement Thickness Fluctuations in Hydroacoustics, and the Jet-Drive Mechanism of the Flue Organ Pipe

Abstract: This paper re-examines a proposal due to Liepmann in which the hydroacoustic effects of a turbulent boundary layer are represented in terms of the displacement thickness fluctuations. The influence of the curvature of the surface that supports the boundary layer is discussed, and in particular the asymptotic condition is obtained under which Liepmann's formalism is applicable in the vicinity of leading and trailing edges. This is important for the theoretical treatment of the interaction of nominally steady flows with wall cavities, slots in aerofoils, splitter plates, etc. Displacement thickness fluctuations in the form of Tollmien-Schlichting waves generated at a leading edge by a disturbance, such as an incident sound wave, are shown to result in a conversion of mean flow energy into sound. At a trailing edge, however, acoustic-mean flow interaction results in the absorption of acoustic energy. A consequence of the leading-edge effect is that it provides an energy transfer mechanism which is capable of maintaining edge tone and cavity oscillations, and this is illustrated by application of the theory to the flue organ pipe. In this case encouraging support for the asymptotic analysis is provided by a comparison with recently published experimental data.

Method and apparatus for producing a plastic sleeve

Abstract: The making of a tubular sleeve of thermoplastic material wherein a strip of sheet stock is fed to a rotatable turret having a plurality of rotatable mandrels thereon, the strip is severed into individual rectangular blanks, each having a leading edge and a trailing edge, each blank is formed into a cylindrical shaped sleeve wrapped around a mandrel with the trailing edge overlapping the exterior of the leading edge of the blank, the mandrels are moved past a sealing station and a plurality of bars are rotated so they move successively in an arcuate path generally tangentially to the path of the blank to bring the sealing surface of each bar into engagement with the overlapped edges and apply radial pressure thereto to fuse the edges together and form a seam.

Leading edge flap for an airfoil

Abstract: © A leading edge flap is provided for an airfoil. The leading edge (24) is rotatably mounted to the airfoil (14). A first flap segment is (48) attached to the leading edge (24) and has an external aerodynamic surface (50a) adapted to form a portion of the bottom aerodynamic surface of the airfoil (14), when the flap (20) is in the retracted position. A second flap segment (60) is pivotally attached to the first flap segment (48) and is adapted to be retracted within a recess (80) within the airfoil (14). A link (70) is pivotally connected to both the second flap segment (60) and the airfoil rib structure (22) such that rotation of the leading edge (24) extends the first and second flap segments (48 and 60) from their retracted positions downwardly and forwardly of the leading edge (24), forming an aerodynamic extension of the airfoil (14). In an additional embodiment, the rotatable leading edge is coupled to a source of heated and/or pressurized air, and contains a spanwise duct (26 ' ) which is adapted to distribute the air along the airfoil (14) heating the leading edge (24') surface so as to remove or prevent ice forming thereon. A plurality of nozzles in the first flap segment (48') are coupled to the duct (26) and/or the bottom surface (142) and adapted to distribute pressurized air over the top surface of the airfoil (14), providing boundary layer control.

Deployable inlet for aeroplane center boost engine

Abstract: A deployable inlet for use with a center boost engine on a jet propelled aircraft having the capability of aerodynamically fairing the air inlet located in the leading edge of the vertical stabilizer at such times as the center boost engine is shut down and non-operative, thus minimizing drag. More particularly, an inlet construction for use with aircraft of the type commonly employing multiple main power plants and an auxiliary center boost engine of the type which is commonly used only: (i) during take-off; (ii) during air refueling operations; and/or (iii), under certain emergency operating conditions; and, wherein the air inlet for such center boost engine is located at the root leading edge of the aircraft's vertical stabilizer. The stabilizer's lower leading edge quarter chord panels define inlet doors for the air inlet, with such doors completely sealing the inlet and lying in the same general plane as the skin surface of the vertical stabilizer when such doors are in the closed position so as to define a smooth continuous airfoil stabilizer surface. In use, the inlet doors defined by the vertical stabilizer lower leading edge quarter chord panels are opened by pivoting outwardly to form the inlet's highlight and throat geometry; yet, when not in use, the inlet doors define a smooth continuation of the vertical stabilizer aerodynamic surfaces, thereby eliminating the need to dedicate additional structure and/or volumetric storage space for such doors.

Airfoil shape for aircraft

Abstract: The invention relates to an airfoil shape for flight at high subsonic speeds, of the type comprising a flat convex upper surface, a thick leading edge and a lower surface convex towards the leading edge and concave towards the trailing, in which airfoil the upper surface comprises a maximum curvature in the vicinity of its rear part, in a zone delimited by points located at distances from the leading edge equal to 65 and 90% of the chord of the airfoil. The invention is applicable to the production of fixed or rotary wings for aircraft, having a high divergence Mach number and a low drag.

The coupling between flow instabilities and incident disturbances at a leading edge

Abstract: It is now generally agreed that an external disturbance field, such as an incident acoustic wave, can effectively couple to instabilities of a flow past a trailing edge. One purpose of the present paper is to show that there are situations where a similar coupling can occur at a leading edge. The process is analyzed and the effects of experimentally controllable parameters are assessed. It is important to account for such phenomena when evaluating the effect of external disturbances on transition.

Calculation of vortex lift effect for cambered wings by the suction analogy

Abstract: An improved version of Woodward's chord plane aerodynamic panel method for subsonic and supersonic flow is developed for cambered wings exhibiting edge separated vortex flow, including those with leading edge vortex flaps. The exact relation between leading edge thrust and suction force in potential flow is derived. Instead of assuming the rotated suction force to be normal to wing surface at the leading edge, new orientation for the rotated suction force is determined through consideration of the momentum principle. The supersonic suction analogy method is improved by using an effective angle of attack defined through a semi-empirical method. Comparisons of predicted results with available data in subsonic and supersonic flow are presented.

Vortex controlled radial diffuser for centrifugal compressor

Abstract: The present invention is an improvement in radial diffusers employed in a turbine engine having a centrifugal compressor The walls of the diffuser define at least one flow passage through the diffuser having a first portion with a first cross-sectional area and a second portion having a larger, second cross-sectional area The first wall section is spaced apart from the second wall section so as to define a bleed aperture therebetween A vortex fence extends outwardly from the wall surface at the leading edge of the second wall portion Preferably, the bleed aperture and the vortex fence are disposed on the suction surface of each vane in a vaned radial diffuser