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  • AERODYNAMICS  (460)
  • Witterung
  • Animals
  • 1975-1979  (463)
  • 1925-1929
  • 1976  (463)
  • 1
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    Direkte und indirekte Folgen der diesjährigen Dürre- und Hitzeperiode (1976)
    In:  Informationen der Hauptstelle für Forstlichen Pflanzenschutz; Nr. 5
    Details
    Publication Date: 1976
    Description: Beschreibung der auf die Dürre- und Hitzeperiode folgenden Schäden durch nadel- und blattfressende Insekten KATASTER-BESCHREIBUNG: Einfluss der Witterung (Temperatur, Niederschlag) auf die Schädlingspopulationen KATASTER-DETAIL: Delta Nied -- und Delta T +, dann Abwehrkraft (Kiefern) - und somit Raupenmortalität -; Delta T (April/Mai) -, dann Zeitpunkt Falterflug - (später); Delta Nied - und Delta T +, dann Buchenrindensterben +;
    Keywords: DDR ; 1975-1976 ; Insekten ; Luftfeuchte ; Buche ; Fichte ; Forst ; Kiefer ; Niederschlag ; Pflanzenschädling ; Temperatur ; Trockenheit ; Wassermangel ; Witterung ; Witterungsextreme
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  • 2
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    Gesamtübersicht des Auftretens der Forleule und der Begleitarten (1976)
    In:  Information der Hauptstelle für Forstlichen Pflanzenschatz; Nr. 3
    Details
    Publication Date: 1976
    Description: Informationen zum Gradationsverlauf der Forleule und ihrer Begleitarten KATASTER-BESCHREIBUNG: Einfluss der Witterung (Temperatur, Niederschlag) auf die Schädlingspopulation KATASTER-DETAIL: Delta T (Winter) + und Delta Nied -, dann Vermehrung (Forleule) ++; Delta T (Frühjahr und Sommer) --, dann Population -; Delta T (März, April) - und Delta Nied (März, April) +, dann Population (Forleule) -;
    Keywords: DDR ; 1972-1976 ; Insekten ; Forst ; Kiefer ; Niederschlag ; Pflanzenschädling ; Temperatur ; Witterung
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  • 3
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    Zentrale Forstschutzkonzeption zur Vermeidung von Folgeschäden in sturmgeschädigten Kiefernbeständen (1976)
    In:  Informationen der Hauptstelle für Forstlichen Pflanzenschutz; Nr. 1
    Details
    Publication Date: 1976
    Description: Beschreibung des Befalls von Kiefernschädlingen und der Maßnahmen zur Vermeidung von Folgeschäden in sturmgeschädigten Kiefernbeständen KATASTER-BESCHREIBUNG: Einfluss der Witterung auf die Entwicklung von Kiefernschädlingen KATASTER-DETAIL: Delta T (Winter) +, dann Entwicklung (rindenbrütende Insekten) +; Delta T (April bis August) und Delta Nied --, dann Entwicklung (rindenbrütende Insekten) +; Delta Wind (=Sturm) +, dann Entwicklung (rindenbrütende Insekten) +;
    Keywords: DDR ; 1976 ; Forst ; Kiefer ; Niederschlag ; Pflanzenschädling ; Sturmschaden ; Temperatur ; Trockenheit ; Witterung
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  • 4
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    Economy of flight at supersonic speeds (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: Prandtl's theory is used to determine the airflow over bodies and wings adapted to supersonic flight. By making use of these results, and by incorporating in them an allowance for the probable skin friction, some estimates of expected lift-drag ratios are made for various flight speeds with the best configuration. At each speed a slender body and wings having the best angle of sweepback are considered. For the range of supersonic speeds shown an airplane of normal density and loading would be required to operate at an altitude of the order of 60,000 feet. The limiting value of 1-1/2 times the speed of sound corresponds to a flight speed of 1000 miles per hour. At this speed about 1.5 miles per gallon of fuel are expected. It is interesting to note that this value corresponds to a value of more than 15 miles per gallon when the weight is reduced to correspond to that of an ordinary automobile.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 499-514
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  • 5
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    Aeroelastic characteristics of an oblique wing (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: In theory, the most efficient wing shape for transonic and low supersonic speeds is simply a long narrow straight subsonic wing turned at an oblique angle to the flight direction. This theory has been verified by tests at Mach numbers from .6 to 1.4 in supersonic wind tunnel and by comparative studies of transonic transport designs.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 867-883
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  • 6
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    Aerodynamic design for supersonic speeds (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: Recent theoretical and experimental work in supersonic aerodynamics is reviewed with its practical application in mind. Several arrangements of supporting surfaces and bodies are discussed and in some cases comparisons of theory and experiment are made. Finally, certain phenomena connected with lift and drag in a rarefied medium are considered briefly.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 625-644
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  • 7
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    Theoretical determination of the minimum drag of airfoils at supersonic speeds (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: A method is reported for determining mathematically the combined disturbance field, and in certain cases the minimum drag, of wings at supersonic speeds. The simplest analytic example is provided by the wing of elliptic planform, which achieves its minimum drag when the lift is distributed uniformly over the surface. With a symmetrical distribution of thickness, the requirement of minimum drag for a given total volume is found to lead to profiles of constant curvature.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 567-578
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  • 8
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    The minimum drag of thin wings in frictionless flow (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: The assumptions of the thin airfoil theory are found to provide certain necessary conditions for the minimum drag of airfoils having a given total lift, a given maximum thickness, or a given volume. The conditions are applicable to steady or unsteady motions and to subsonic or supersonic speeds without restriction on the planform. The computation of drag and the statement of the conditions for minimum drag depend on the consideration of a combined flow field, which is obtained by superimposing the disturbance velocities in forward and reversed motions. If the planform of the airfoil and its total lift are given, it is found that, for minimum drag, the lift must be distributed in such a way that the downwash in the combined field is constant over the entire planform. If the planform is given and the thickness of the airfoil is required to contain a specified volume, then the thickness must be distributed over the planform in such a way that the pressure gradient of the combined field in the direction of flight is constant at all points of the wing.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 557-565
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  • 9
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    Calculation of the motion of an airplane under the influence of irregular disturbances (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: The application of mathematical advances made in electricity and other branches to problems of airplane dynamics is demonstrated. The Heaviside-Bromwich methods of solution of linear differential equations are described and it is shown how these methods avoid the consideration of boundary conditions and of particular or complementary integrals. It is pointed out that if the solution of the differential equation is obtained for the case of a unit disturbance, the effect of varying disturbances may be found therefrom by Carson's theorem. A graphical solution of Carson's integral for irregular disturbances is given. The procedure of obtaining unit solutions of the equations is then taken up and the analogy between Heaviside's symbolic series solution and a physical procedure of approximation is shown. It is suggested that a fictitious impulsive disturbance be used in the treatment of initial motions.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 21-29
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  • 10
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    Three-dimensional wings of minimum pressure drag (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: In linearized flow theory, certain very interesting extremal properties of wings can be derived under rather broad conditions without the use of a complicated mathematical apparatus. The present chapter reviews certain results of this theory and indicates some rather obvious extensions to incorporate various auxiliary conditions. Several examples illustrating the relation between the geometrical features of the wing and the lift distribution for minimum drag are given.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Collected Works of Robert T. Jones; p 645-656
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  • 11
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    Some recent developments in the aerodynamics of wings for high speeds (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: The items discussed are: (1) a recently proposed correction formula for the effect of compressibility in two dimensional subsonic flow; (2) the equivalence rule and the area rule for transonic speeds; (3) reciprocal relations in linearized wing theory; and (4) some general results connected with the problem of minimum wave resistance. The paper concludes with an example showing indentation of the fuselage to obtain favorable interference with the wing at supersonic speeds.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 601-608
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  • 12
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    Theoretical correction for the lift of elliptic wings (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: In the wing section theory the magnitude of the circulation, and hence of the lift, is determined by the velocity that would be induced near the trailing edge of the section in a non-lifting potential flow. In three dimensional flow the problem is complicated by the presence of the wake and no simple basic solution has been found. Treatment of the problem of a wing of finite span is reported on the basis of the two dimensional theory, corrected for the effect of the wake.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 245-249
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  • 13
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    Reduction of wave drag by antisymmetric arrangement of wings and bodies (1976)
    In:  CASI
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    Publication Date: 2010-11-08
    Description: In theory, antisymmetric arrangements of wings and bodies can have smaller wave drag than corresponding mirror-symmetric arrangements. Thus, a long narrow oblique wing which presents the same aspect for two opposite directions of flight is potentially more efficient than corresponding (i.e., structurally equivalent) swept wing. The single continuous wing panel also adapts itself more readily to varying angles of obliquity, and hence, to varying flight speeds. Previous work on the aerodynamics and flight stability of oblique wing combinations is reviewed and a possible mode of application to transport aircraft operating at moderate supersonic speeds is suggested.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 657-664
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  • 14
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    The compressibility rule for drag of airfoil noses (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: It is shown that the drag of any semi-infinite airfoil section in purely subsonic inviscid flow follows precisely the Prandtl-Glauert compressibility rule. The result for the parabola has application to leading edge corrections in thin airfoil theory.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 619-623
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  • 15
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    Possibilities of efficient high-speed transport airplanes (1976)
    In:  CASI
    Details
    Publication Date: 2010-11-08
    Description: Comparisons of wing-body combinations may not disclose the full effect of a loss in aerodynamic efficiency. If the thrust needs to be increased at a given altitude then more or larger engines will have to be used and the possibility of concealing them becomes less. In this process the lift drag ratio of the complete airplane may become still more unfavorable than indicated by the comparison. Primarily aerodynamic and structural considerations point toward the development of turbojet engines specifically adapted to operation in an atmosphere of one tenth normal density. In addition to the numerous other technological problems associated with operation at these high altitudes, the problems of safe descent and effective limitation to low speeds at low altitudes seem important.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 579-592
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  • 16
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    Leading-edge singularities in thin-airfoil theory (1976)
    In:  CASI
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    Publication Date: 2010-11-08
    Description: If the thin airfoil theory is applied to an airfoil having a rounded leading edge, a certain error will arise in the determination of the pressure distribution around the nose. It is shown that the evaluation of the drag of such a blunt nosed airfoil by the thin airfoil theory requires the addition of a leading edge force, analogous to the leading edge thrust of the lifting airfoil. The method of calculation is illustrated by application to: (1) The Joukowski airfoil in subsonic flow; and (2) the thin elliptic cone in supersonic flow. A general formula for the edge force is provided which is applicable to a variety of wing forms.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 533-538
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  • 17
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    The use of conical and cylindrical fields in supersonic wing theory (1976)
    In:  CASI
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    Publication Date: 2010-11-08
    Description: Some of the recent advances in the theory of thin airfoils are presented with particular reference to extensions of the theory to three dimensional flows and to supersonic speeds. The problem discussed herein is the calculation of the small disturbance velocities u, v, and w in the external field produced by the flight velocity V of the airfoil.
    Keywords: AERODYNAMICS
    Type: Collected Works of Robert T. Jones; p 483-497
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  • 18
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    The lateral flying qualities of the Bell XP-77 airplane as estimated from full-scale tunnel tests, 16 June 1944 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Results are presented for tests made of the full scale model of the airplane in the NACA full scale tunnel. These tests were planned so as to cover as completely as possible the lateral flying quality requirements for pursuit-type airplanes contracted for by the United States Army Air Forces.
    Keywords: AERODYNAMICS
    Type: Collected Works of Charles J. Donlan; 23 p
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  • 19
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    Three dimensional boundary layer separation in supersonic flow (1976)
    In:  CASI
    Details
    Publication Date: 2011-10-14
    Description: An account is given of a detailed experimental investigation of three dimensional boundary layer separation in supersonic flow. In investigating three dimensional effects on supersonic separation, models were chosen which exhibited departures from two dimensional flow in the simplest way. The plane compression corner was replaced by a plate attached to a swept back wedge formed by two obliquely intersecting planes. Maintaining a constant tunnel Mach number of 2.5, surface pressure measurements were made on these models at static orifices spaced along the centerline and along three parallel lines. The flow parameters in the boundary layer and separated regions adjacent to the model surface were measured by traversing hot wire and pitot probes. The traverses were taken across the boundary layer and reversed flow regions in a direction normal to the body surface; they were made in several vertical planes, including the plane of symmetry.
    Keywords: AERODYNAMICS
    Type: AGARD Flow Separation; 13 p
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  • 20
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    Numerical solution of the steady-state Navier-Stokes equations for hypersonic flow about blunt axisymmetric bodies (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The steady-state Navier-Stokes equations are solved for hypersonic flow about blunt axisymmetric bodies. The equations of motion are solved by successive approximations using an implicit finite-difference scheme. The results are compared with viscous shock-layer theory, experimental data, and time-dependent solutions of the Navier-Stokes equations. It is demonstrated that viscous shock-layer theory is sufficiently accurate for the range of flight conditions normally encountered by entry vehicles.
    Keywords: AERODYNAMICS
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  • 21
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    Aerodynamic heat transfer to a hypersonic research aircraft model /X-24C/ at Mach 6 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper reports on results of heat-transfer tests conducted on a 1/29-scale model of the X-24C-12I hypersonic research aircraft configuration in a Mach 6 tunnel at a Reynolds number of thirteen million using the phase-change heat transfer technique. Sequences of phase-change heat transfer pattern photographs are presented showing windward side and leeward side heating processes. Theoretical predictions of dimensionless heat transfer coefficients along a data line on lower fuselage and on fuselage side bracket the experimental values. A turbulent heating theory gives good agreement with data when shifted to a new virtual origin.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 13; Dec. 197
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  • 22
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    Skin friction on a flat perforated acoustic liner (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The report concerns the measurement of friction coefficients of a typical perforated acoustic liner installed in the side of a wind tunnel. The results are compared with measured friction coefficients of a smooth hard wall for the same mean flow velocities in a wind tunnel. At a velocity of 61 m/sec, an increase in the local skin coefficient of only a few percent was observed, but at the highest velocity of 213 m/sec an increase of about 20% was obtained. This velocity is a realistic velocity for turbo-machinery components utilizing such liners, so a loss in performance is to be expected. Some tests were also performed to see if changes in the mean boundary layer induced by imposed noise would result in friction increase, but only at low velocity levels was such an increase in friction noted.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 14; Nov. 197
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  • 23
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    Steady supersonic flowfields with embedded subsonic regions (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Supersonic flow past a blunt body is considered, where the flow contains an embedded subsonic region which lies between the shock wave and the body surface and is bounded by sonic lines from the body to the shock. A numerical approach is taken, which uses a basic finite difference scheme that solves the unsteady fluid dynamic equations in integral form. The unsteady equations are everywhere hyperbolic in time so no distinction need be made between subsonic and supersonic regions. Solutions to the mixed elliptic and hyperbolic steady flow equations are approached asymptotically in time. The method is illustrated for two-dimensional flows.
    Keywords: AERODYNAMICS
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  • 24
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    Improved interactive calculation procedure for supersonic flows (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An interactive numerical procedure has been developed for supersonic viscous flows (either two-dimensional or axisymmetric configurations). The flow field is divided into two regions: (1) an inner region which is highly viscous and mostly subsonic, and (2) an outer region where the flow is supersonic and in which viscous effects are small, but not negligible. This paper presents a detailed description of: I. Outer Region - numerical solution obtained by applying the method of characteristics to a system of equations which includes viscous and conduction transport terms only normal to the streamlines; II. Inner Region - treated by a system of equations of the boundary-layer type that includes higher order effects, such as longitudinal and transverse curvature and normal pressure gradients (equations are coupled and solved simultaneously in physical coordinates, using an implicit finite-difference scheme); III. Interactive Procedure - in the interaction mode, the two regions are coupled iteratively along a matching line, where the Mach number is of the order of 1.2.
    Keywords: AERODYNAMICS
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  • 25
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    Influence of nonconservative differencing on transonic streamline shapes (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A computer program recently developed by South and Brandt (1976) which contained the Murman (1973) conservative finite-difference scheme is easily modified to use the Garabedian and Korn (1971) nonconservative finite difference scheme. This program solves the transonic small disturbance equation for only symmetric flow, but incorporates several iterative solution techniques. Results are presented for the case where the equally spaced computational grid extended to infinity in both the streamwise and normal directions. Streamline shapes are obtained along several grid lines by a streamwise integration of the normal component of the perturbation velocity. Comparison cases are run for a 10% thick parabolic arc airfoil at zero incidence for freestream Mach numbers of 0, 0.70, 0.84, and 0.95. It is shown that the use of a nonconservative finite-difference scheme in transonic flow calculations destroys the global mass balance when shocks are present. This lack of mass balance may prove to be more crucial in the case of an unconfined external flow.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 14; Aug. 197
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  • 26
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    Vortex shedding from a blunt trailing edge with equal and unequal external mean velocities (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A flow-visualization study has shown that strong Karman vortices develop behind the blunt trailing edge of a plate when the free-stream velocities over both surfaces are equal and that the vortices tend to disappear when the surface velocities are unequal. This observation provides an explanation for the occurence and disappearance of certain discrete tones often found to be present in the noise spectra of coaxial jets. Both the vortex formation and the tones occur at a Strouhal number based on the lip thickness and the average of the external steady-state velocities of about 0.2. Results from theoretical calculations of the vortex formation, based on an inviscid incompressible analysis of the motion of point vortices, were in good agreement with the experimental observations.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 75; June 25
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  • 27
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    Atmospheric entry into Jupiter's atmosphere in view of recent flyby results (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The paper examines the heating levels experienced by a probe entering Kliore's (1974) model of Jupiter's atmosphere and compares the results with those of the Jupiter model atmospheres given elsewhere (NASA SP-8069, 1971), with the heating levels of Tauber (1969) and Tauber and Wakefield (1971). The computations are made using a point-mass atmospheric entry trajectory program, i.e., the Allen-Eggers (1958) analysis and simple correlations of heating. Results of heating calculations are compared and discussed. It is found that the warm temperature bulge exists at a level too low in the atmosphere to affect any heating and that the nominal atmosphere fits Kliore's model atmosphere best insofar as heating is concerned. Previous estimates of the heating levels to be expected for a probe entering Jupiter's atmosphere are therefore unaffected by Kliore's postulated atmospheres.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets; 13; Feb. 197
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  • 28
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    Roughness induced transition criteria for space shuttle-type vehicles (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Tripping effectiveness of surface roughness on a delta wing shuttle orbiter model at 20 deg angle of attack is compared to that on plane and axisymmetrical bodies with and without longitudinal pressure gradients. The experimental data presented are compared on the basis of effective roughness Reynolds number since this parameter is not sensitive to flow conditions downstream of the roughness. The discussion covers the effective roughness Reynolds number as a function of roughness position Reynolds number, effective size ratio as a function of pressure gradient and distance from vehicle nose, and effect of spanwise roughness position on roughness effectiveness. It is shown that conventional criteria for sizing roughness elements which promote transition in two-dimensional zero-pressure gradient flows are insufficient for high-pressure gradient flows and three-dimensional flows. Roughness much smaller than that given by conventional criteria can cause transition and significantly increase the heating load.
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets; 13; Feb. 197
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  • 29
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    A complete second-order theory for the unsteady flow about an airfoil due to a periodic gust (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A uniformly valid second-order theory is developed for calculating the unsteady incompressible flow that occurs when an airfoil is subjected to a convected sinusoidal gust. Explicit formulas for the airfoil response functions (i.e., fluctuating lift) are given. The theory accounts for the effect of the distortion of the gust by the steady-state potential flow around the airfoil, and this effect is found to have an important influence on the response functions. A number of results relevant to the general theory of the scattering of vorticity waves by solid objects are also presented.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 74; Apr. 22
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  • 30
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    A technique for accelerating iterative convergence in numerical integration, with application in transonic aerodynamics (1976)
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    Publication Date: 2011-08-16
    Description: A technique is described for the efficient numerical solution of nonlinear partial differential equations by rapid iteration. In particular, a special approach is described for applying the Aitken acceleration formula (a simple Pade approximant) for accelerating the iterative convergence. The method finds the most appropriate successive approximations, which are in a most nearly geometric sequence, for use in the Aitken formula. Simple examples are given to illustrate the use of the method. The method is then applied to the mixed elliptic-hyperbolic problem of steady, inviscid, transonic flow over an airfoil in a subsonic free stream.
    Keywords: AERODYNAMICS
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  • 31
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    Inlets for high angles of attack (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Different inlet designs for high angle of attack STOL and VTOL applications were tested in a subsonic wind tunnel. Three removable entry lips having contraction ratios of 1.30, 1.34 and 1.38 were tested with a single diffuser. The internal contour of each entry lip was an ellipse with a major to minor axis of 2.0. Each lip and diffuser assembly was tested to determine its tolerance to angle of attack, first with a conventional centerbody and then with an extended centerbody. Results indicate that a large improvement in separation angle (determined as a function of lip contraction ratio and inlet flow) was obtained for the extended centerbody for all contraction ratios. Improved inlet tolerance to angle of attack was obtained by reducing the adverse pressure gradient downstream of the throat.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 13; Apr. 197
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  • 32
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    Effect of geometry modifications on effectiveness of slot injection in hypersonic flow (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The study presents wind-tunnel measurements of surface static pressures, equilibrium temperatures, and skin friction downstream of tangential slot injection into a thick turbulent hypersonic boundary layer from two modified slot configurations. The data are compared with results obtained for baseline configurations reported by Cary and Hefner (1970, 1972) to determine whether simple modifications to the slot configuration can produce improved cooling effectiveness and skin friction reduction. The baseline slot configurations are simply modified by thickening the slot lip and by elevating the location of the slot exit above the flat plate. Although the results indicate that simple modifications of the baseline slot configurations can enhance the skin friction reductions obtained with tangential slot injection, slot base drag estimates show that neither of the modifications will lessen the impact of the systems penalties for collecting, ducting, and injecting the slot air.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 14; June 197
    Format: text
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  • 33
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    Turbulence measurements in hypersonic shock-wave boundary-layer interaction flows (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Turbulent intensity and Reynolds shear stress measurements are presented for two nonadiabatic hypersonic shock-wave boundary-layer interaction flows, one with and one without separation. These measurements were obtained using a new hot-wire probe specially designed for heated flows. Comparison of the separated and attached flows shows a significant increase above equilibrium values in the turbulent intensity and shear stress downstream of the interaction region for the attached case, while for the separated case, the turbulent fluxes remain close to equilibrium values. This effect results in substantial differences in turbulence lifetime for the two flows. We propose that these differences are due to a coupling between the turbulent energy and separation bubble unsteadiness, a hypothesis supported by the statistical properties of the turbulent fluctuations.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 14; May 1976
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  • 34
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    Application of radial-splitters for improved wide-angle diffuser performance in a blowdown tunnel (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Severe flow separation in the 15:1 area-ratio, 38 deg total angle conical diffuser preceding the settling-chamber of an intermittent blowdown wind tunnel was eliminated by the use of a novel radial-splitter arrangement. As a consequence, the operating life of settling-chamber screens was greatly extended and test-section flow steadiness improved, with no penalty in the tunnel running time.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 13; July 197
    Format: text
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  • 35
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    Status and prospects of computational fluid dynamics (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The use and limitations on using computational aerodynamics in approximating inviscid linear, inviscid nonlinear, vicous time averaged, and viscous time dependent flow past airfoils, wings, and aircraft is reviewed. The current status of two- and three-dimensional time averaged Navier-Stokes equation is discussed and possible applications for the 1980 and 1985 to 1990 period is projected for three-dimensional applications.
    Keywords: AERODYNAMICS
    Type: Von Karman Inst. for Fluid Dyn. Computational Fluid Dyn., Vol. 2; 36 p
    Format: text
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  • 36
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    Some recent progress in transonic flow computation (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Although the development of a finite difference relaxation procedure to solve the steady form of equations of motion gave birth to the study of computational transonic aerodynamics and considerable progress has been made using the small disturbance theory, no general analytical solution method yet exists for transonic flows that include three dimensional unsteady, and viscous effects. Two techniques are described which are useful in computational transonic aerodynamics applications. The finite volume method simplifies the application of boundary conditions without introducing the constriction associated with small disturbance theory. Governing equations are solved in a Cartesian coordinate system using a body-oriented and shock-oriented mesh network. Only the volume and surface normal directions of the volume elements must be known. The other method, configuration design by numerical optimization, can be used by aircraft designers to develop configurations that satisfy specific geometric performance constraints. Two examples of airfoil design by numerical optimization are presented.
    Keywords: AERODYNAMICS
    Type: Von Karman Inst. for Fluid Dyn. Computational Fluid Dyn., Vol. 1; 122 p
    Format: text
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  • 37
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    Calculation methods for compressible turbulent boundary layers (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Calculation procedures for non-reacting compressible two- and three-dimensional turbulent boundary layers were reviewed. Integral, transformation and correlation methods, as well as finite difference solutions of the complete boundary layer equations summarized. Alternative numerical solution procedures were examined, and both mean field and mean turbulence field closure models were considered. Physics and related calculation problems peculiar to compressible turbulent boundary layers are described. A catalog of available solution procedures of the finite difference, finite element, and method of weighted residuals genre is included. Influence of compressibility, low Reynolds number, wall blowing, and pressure gradient upon mean field closure constants are reported.
    Keywords: AERODYNAMICS
    Type: Von Karman Inst. for Fluid Dyn. Compressible Turbulent Boundary Layers, Vol. 2; 124 p
    Format: text
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  • 38
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    USB environment measurements based on full-scale static engine ground tests (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Flow turning parameters, static pressures, surface temperatures, surface fluctuating pressures and acceleration levels were measured in the environment of a full-scale upper surface blowing (USB) propulsive lift test configuration. The test components included a flightworthy CF6-50D engine, nacelle, and USB flap assembly utilized in conjunction with ground verification testing of the USAF YC-14 Advanced Medium STOL Transport propulsion system. Results, based on a preliminary analysis of the data, generally show reasonable agreement with predicted levels based on model data. However, additional detailed analysis is required to confirm the preliminary evaluation, to help delineate certain discrepancies with model data, and to establish a basis for future flight test comparisons.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 479-496
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  • 39
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    NASA participation in the AMST program (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The objectives of the NASA Advanced Medium STOL Transport Experiments Program are discussed and several of the NASA experiments currently implemented and conducted on the YC-14 and YC-15 prototype aircraft are described. Emphasis is placed on experiments related to powered lift aerodynamics and acoustics.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 465-478
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  • 40
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    Investigations of scaling laws for jet impingement (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The statistical properties of tangential flows over surfaces were investigated by two techniques. In one, a laser-Doppler velocimeter was used in a smoke-laden jet to measure one-point statistical properties, including mean velocities, turbulent intensities, intermittencies, autocorrelations, and power spectral densities. In the other technique, free stream and surface pressure probes connected to 1/8 inch microphones were used to obtain single point rms and 1/3 octave pressures, as well as two point cross correlations, the latter being converted to auto spectra, amplitude ratios, phase lags, and coherences. The results of these studies support the vortex model of jets, give some insights into the effects of surface impingement, and confirm that jet diameter and velocity are the scaling parameters for circular jets, while Reynolds number is relatively unimportant.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 445-463
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  • 41
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    Measured and calculated steady aerodynamic loads on a large-scale upper-surface blown model (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Static aerodynamic loads measurements from wind tunnel tests of a full-scale upper surface blown jet flap configuration are presented. The measured loads are compared with calculations using a method for predicting longitudinal aerodynamic characteristics of upper surface blown jet flap configurations.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 415-428
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  • 42
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    Acoustic-loads research for powered-lift configurations (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Data presented from large-scale model tests with jet engines having thrusts of 9 kN (2000 lb) and 36 kN (8000 lb) include acoustic loads for an externally blown wing and flap induced by a TF34 jet engine, an upper surface blown (USB) aircraft model in a wind tunnel, and two USB models in static tests. Comparisons of these results with results from acoustic loads studies on configurations of other sizes are made and the implications of these results on interior noise and acoustic fatigue are discussed.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 429-443
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  • 43
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    Acoustics and aerodynamics of over-the-wing thrust reversers (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: As part of the Quiet Clean Short-Haul Experimental Engine Program, model tests were conducted to determine the effects of thrust reverser geometric parameters on noise and reverse thrust. The acoustic tests used a 1/6 scale model thrust reverser while the aerodynamic performance tests used a 1/12 scale model reverser. Parameters which were varied in both tests include blocker spacing, blocker height, lip angle, and lip length. The impact of these parameters on peak sideline noise and reverse thrust performance is discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 403-414
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  • 44
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    Reverse-thrust technology for variable-pitch fan propulsion systems (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Tests conducted to develop the technology necessary to meet the unique reverse-thrust performance requirements of a variable pitch fan propulsion system are discussed. The losses and distortion associated with the air entering the fan and core compressor from the rear of the engine, the direction of fan blade pitch rotation for best reverse-thrust aeroacoustic performance, and engine response and operating characteristics during forward- to reverse-thrust transients are among the factors studied. The test results of several scale fan models as well as a full-size variable pitch fan engine are summarized. Results show the following: a flared exhaust nozzle makes a good reverse-thrust inlet; acceptable core inlet duct recovery and distortion levels in reverse flow were demonstrated; adequate thrust levels were achieved; forward- to reverse-thrust response time achieved was better than the goal; thrust and noise levels strongly favor reverse through feather pitch; and finally, flight-type inlets make the establishment of reverse flow more difficult.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 387-402
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  • 45
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    Inlet technology for powered-lift aircraft (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The concepts, analytical tools, and experimental data available for designing inlets for powered lift aircraft are discussed. It is shown that inlets can be designed to meet noise, distortion, and cruise drag requirements at the flight and engine operating conditions of a powered lift aircraft. The penalty in pressure recovery for achieving the required noise suppression was 0.3 percent.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 369-385
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  • 46
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    Inlet/nacelle/exhaust system integration for the QCSEE propulsion systems (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The key features of the integrated propulsion systems developed for short haul aircraft are discussed including the high Mach number, fixed geometry, near sonic inlet, the variable area nozzles, thrust reversing systems, and aircraft accessory location. The roles and interplay of each element are considered and comparisons are made with conventional state-of-the-art technology.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 357-367
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  • 47
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    Acoustic design of the QCSEE propulsion systems (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Acoustic design features and techniques employed in the Quiet Clean Short-Haul Experimental Engine (QCSEE) Program are described. The role of jet/flap noise in selecting the engine fan pressure ratio for powered lift propulsion systems is discussed. The QCSEE acoustic design features include a hybrid inlet (near-sonic throat velocity with acoustic treatment); low fan and core pressure ratios; low fan tip speeds; gear-driven fans; high and low frequency stacked core noise treatment; multiple-thickness treatment; bulk absorber treatment; and treatment on the stator vanes. The QCSEE designs represent and anticipated acoustic technology improvement of 12 to 16 PNdb relative to the noise levels of the low-noise engines used on current wide-body commercial jet transport aircraft.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 335-356
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  • 48
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    Overview of the QCSEE program (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Externally blown flap and upper surface blown flap powered lift concepts were investigated in the Quiet Clean Short-Haul Experimental Engine Program and briefly discussed along with propulsion system requirements. Noise limits, emission standards, thrust requirements, and thrust-to-weight ratios are among the factors considered.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 325-333
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  • 49
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    EBF noise reduction through nozzle/flap positioning (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results are presented of an experimental and analytical study of the dependence of externally blown flap (EBF) noise on the relative position and shape of engine exhaust nozzle. Tests, conducted on a 1/15 scale model of a triple-slotted EBF system, indicate that a significant reduction (of up to 10 to 15 db for no forward speed case and of up to 5 to 10 db for forward speed case) is possible in the low frequency (around 63 Hz) region of the noise spectrum of the full scale device for small nozzle/flap separation distances. The overall acoustic performance, measured in PNdb, does not exhibit significant reductions. The analysis of the EBF noise is carried out for two limiting airfoil in a free jet. The analytical results also suggest that low frequency noise can be reduced by placing the nozzle close to the flow turning elements.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 307-324
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  • 50
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    USB noise reduction by nozzle and flap modifications (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The development of concepts for reducing upper surface blown flap noise at the source through flap modifications and special nozzles is reviewed. In particular, recent results obtained on the aerodynamic and acoustic performance of flaps with porous surfaces near the trailing edge and multi-slotted nozzles are reviewed. Considerable reduction (6-10 db) of the characteristic low frequency peak is shown. The aerodynamic performance is compared with conventional systems, and prospects for future improvements are discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 283-305
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  • 51
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    Analytical modeling of under-the-wing externally blown flap powered-lift noise (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The sound field produced by the interaction of a subsonic jet with a large-scale model of the under the wing externally blown flap in an approach attitude was analyzed. The analysis was performed to obtain a better understanding of the dominant noise sources and the mechanisms governing the peak sound pressure level frequencies of the broadband spectra. An analytical expression is derived which incorporates two available theories and experimental data; the expression predicts the sound field along a circular arc of approximately 120 deg measured from the upstream jet axis in the fly-over plane. The analysis compares favorably with test results obtained from two large-scale models, one using cold air from a conical nozzle and the other using hot gas from a TF-34 turbofan engine having a conical exhaust nozzle with a 12 lobe internal forced mixer. The frequency at which the peak sound pressure level occurs appears to be governed by a phenomenon which produces periodic formation and shedding of large-scale turbulence structures from the nozzle lip.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 263-282
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  • 52
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    USB flow characteristics related to noise generation (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The effects of nozzle and flap geometry on upper surface blown flow field characteristics related to noise generation were examined experimentally using static models. Flow attachment and spreading characteristics were observed using flow visualization techniques. Velocity and turbulence profiles in the trailing edge wake were measured using hot-wire anemometry, and the effects of the geometric variables on peak velocity and turbulence intensity were determined. It is shown that peak trailing edge velocity is a function of the ratio of flow length to modified hydraulic diameter.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 213-226
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  • 53
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    Effects of nozzle design and power on cruise drag for upper-surface-blowing aircraft (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A high speed wind tunnel investigation was conducted on a series of upper surface blowing nozzles with D-shaped exits installed on a representative short haul aircraft model. Both two and four engine configurations were investigated. Powered engine simulators were used to properly represent nacelle flows. Large differences in cruise drag penalties associated with the various nozzle designs were seen. Some geometric parameters influencing nozzle cruise drag are identified.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 183-196
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  • 54
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    Distributed upper-surface blowing concept (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A low speed investigation was conducted in the Langley V/STOL tunnel to determine the powered lift aerodynamic performance of a distributed upper surface blown propulsive lift transport model. The model used blowing slots across the span of the wing to produce a thin jet efflux near the leading edge and at the knee of the trailing edge flap (internally blown jet flap). Results indicate that these concepts have both good propulsive related lift and low drag due to lift characteristics because of uniform spanwise propulsive thrust. The leading edge blowing concept provides low speed lift characteristics which are competitive with the flap-hinge-line blowing concept and does not require additional leading edge treatment for prevention of abrupt stall.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 159-164
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  • 55
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    Aerodynamic characteristics in ground proximity (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results from recent investigations in the Langley V/STOL tunnel of an externally blown flap and an upper surface blown flap configuration in ground proximity are presented. Comparisons of longitudinal aerodynamic characteristics indicate that in ground proximity, drag is reduced for both configurations, but changes in lift are configuration dependent. Steady state analyses of the landing approach indicate an increase in flight path angle for both configurations in ground proximity because of the drag reduction. Dynamic analyses with a fixed-base simulator indicate that the resultant flight path during landing approach is dependent on the initial flight path angle and the control technique used.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 145-158
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  • 56
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    Some measurements of an EBF powered-lift wake (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results from a wind tunnel investigation in which velocity vector measurements were obtained in the near wake of an externally blown flap powered lift configuration were analyzed. These measurements were used to develop spanwise distributions for the momentum strength and location of the engine exhaust stream tube with the results used as input parameters to one jet flap analytical method. It is shown that a comparison of the momentum coefficients obtained from forward speed wake surveys with the predicted values from static force data results in a good correlation, which verifies the use of the flap thrust recovery factor as a means of predicting the momentum strength at the flap trailing edge. Also, when wake survey distributions of momentum strength and direction are used as input parameters to one analytical jet flap method, the results show reasonable agreement between the experimental data and analytical results.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 135-143
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  • 57
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    Externally blown flap impingement parameters (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The performance of two externally blown flap (EBF) wind tunnel models was compared with an engine exhaust flap impingement correlation parameter. One model was a four engine EBF triple slotted flap transport. Isolated engine wake surveys were conducted to define the wake properties of five separate engine configurations for which performance data were available. The other model was a two engine EBF transport for which the engine wake properties were estimated. The correlation parameter was a function of engine exhaust dynamic pressure at the flap location, area of engine exhaust flap impingement, total exhaust area at the flap location, and engine thrust. The distribution of dynamic pressure for the first model was measured; however, the distribution for the second model was assumed to be uniform.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 119-134
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  • 58
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    Application of powered-lift concepts for improved cruise efficiency of long-range aircraft (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results of studies conducted to explore the use of powered lift concepts for improved low speed performance of long range subsonic and supersonic cruise vehicles are summarized. It is indicated that powered lift can provide significant improvements in low speed performance, as well as substantial increases in cruise efficiency and range for both subsonic and supersonic cruise configurations.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 89-101
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  • 59
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    Summary of low-speed aerodynamic characteristics of upper-surface-blown jet-flap configurations (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The results of recent wind tunnel investigations to provide fundamental information on the upper surface blown (USB) jet flap concept demonstrated that the USB concept provides good high-lift performance. It is shown that the low speed performance is dependent upon the jet turning angle and turning efficiency and on the use of proper leading and trailing edge treatment to prevent premature flow separation. The best means of achieving good turning performance in any particular USB application must be determined from overall operational considerations in which high speed performance, structures and noise, as well as low speed performance, are evaluated. The large diving moments generated at high lift coefficients can be trimmed satisfactorily with a large, conventional horizontal tail; a high tail position is best from longitudinal stability considerations. Large rolling and yawing moments are introduced with the loss of an engine, but these moments can be trimmed satisfactorily through the use of asymmetrical boundary layer control and through the use of spoiler and rudder deflection as needed.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 63-87
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  • 60
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    Results of static tests of a 1/4 scale model of the Boeing YC-14 powered-lift system (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: One quarter scale static ground tests of the Boeing YC-14 powered lift system were conducted for correlation with full scale test results. The 1/4 scale model utilized a JT-15D turbofan engine to represent the CF6-50D engine employed on the YC-14 advanced medium STOL transport prototype aircraft. The tests included evaluation of static turning performance, static surface pressure and temperature distributions, fluctuating loads, and accelerations of portions of the wing, flaps, and fuselage. Results are presented for the landing flap configuration over an appropriate range of fan pressure ratio as affected by several variables including ground height and vortex generator modifications. Static turning angles of the order of 60 deg were obtained. The highest surface pressures and temperatures were concentrated over the upper surface of the flaps in the region immediately aft of the upper surface blown nozzle.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 45-62
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  • 61
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    Comparison of aerodynamic theory and experiment for jet-flap wings (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Aerodynamic theory predictions made for a jet flapped wing were compared with experimental data obtained in a fairly extensive series of tests in the Langley V/STOL tunnel. The tests were made on a straight, rectangular wing and investigated two types of jet flap concepts: a pure jet flap with high jet deflection and a wing with blowing at the knee of a plain trailing edge flap. The tests investigated full and partial span blowing for wing aspect ratios of 8.0 and 5.5 and momentum coefficients from 0 to about 4. The total lift, drag, and pitching moment coefficients predicted by the theory were in excellent agreement with experimental values for the pure jet flap, even with the high jet deflection. The pressure coefficients on the wing, and hence the circulation lift coefficients, were underpredicted, however, because of the linearizing assumptions of the planar theory. The lift, drag, and pitching moment coefficients, as well as pressure coefficients, were underpredicted for the wing with blowing over the flap because of the failure of the theory to account for the interaction effect of the high velocity jet passing over the flap.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 103-118
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    Upper-surface-blowing flow-turning performance (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Jet exhaust flow-turning characteristics were determined for systematic variations in upper-surface blowing exhaust nozzles and trailing-edge flap configuration variables from experimental wind-off (static) flow studies. For conditions with parallel flow exhausting from the nozzle, jet height (as indicated by nozzle exit height) and flap radius were found to be the most important parameters relating to flow turning. Nonparallel flow from the nozzle, as obtained from an internal roof angle and/or side spread angle, had a large favorable effect on flow turning. Comparisons made between static turning results and wind tunnel aerodynamic studies of identical configurations indicated that static flow-turning results can be indicative of wind-on powered lift performance for both good and poor nozzle-flap combinations but, for marginal designs, can lead to overly optimistic assessment of powered lift potential.
    Keywords: AERODYNAMICS
    Type: Powered-Lift Aerodyn. and Acoustics; p 29-43
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  • 63
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    Overview of powered-lift technology (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The concept and application of powered lift and the effects of some fundamental design variables are discussed. A brief chronology of significant developments in the field is also presented and the direction of research efforts in recent years is indicated. All powered lift concepts are included, but emphasis is on the two externally blown schemes which involve blowing either above or below the wing and which are utilized in the YC-14 and YC-15 aircraft. Aerodynamics and vehicle design are emphasized. The areas of acoustics, propulsion, and loads are briefly considered.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Powered-Lift Aerodyn. and Acoustics; p 1-27
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  • 64
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    Experiments planned specifically for developing turbulence models in computations of flow fields around aerodynamic shapes (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Building block experiments and companion numerical simulations intended to verify and guide turbulence modeling are described. A series of experiments and computations being used to enhance modeling development for the shock wave turbulent boundary layer interaction problem is emphasized. Results are given for transonic flow over a circular arc airfoil undergoing shock wave induced, boundary layer separation for supersonic flow along a tube wall undergoing normal shock wave induced, boundary layer separation. Experimental data which use the complete Navier-Stokes equations are discussed.
    Keywords: AERODYNAMICS
    Type: AGARD Numerical Methods and Windtunnel Testing; 13 p
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  • 65
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    Persistence and decay of wake vorticity (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Some recent research relating to the nature of the lift-induced vortex wakes behind large aircraft was reviewed and the scaling laws that permit a comparison of results from ground facilities with those from flight test were provided. The maximum rotational velocities in the wake are shown to depend on a span loading shape parameter and on a characteristic length of persistence behind the aircraft. The effects of Reynolds number are also shown.
    Keywords: AERODYNAMICS
    Type: AGARD Flight(Ground Testing Fac. Correlation; 10 p
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  • 66
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    Prepared comment on the cone transition Reynolds number data correlation study (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: A sharp, smooth, 10-deg-included-angle cone was tested on twenty-one major wind tunnels of the United States and Western Europe to obtain correlation data on the effect of acoustic disturbances in wind tunnel flow on boundary layer transition Reynolds number. The cone is planned to be flight tested in order to obtain a basis of reference for the wind tunnel data over a nominal range of Mach numbers from 0.4 to approximately 2.0. Wind tunnel data obtained over a Mach number range from 0.2 to 4.6 are broadly characterized according to wind tunnel test section geometry and, in turn, to the types of acoustic disturbances associated with the geometry.
    Keywords: AERODYNAMICS
    Type: AGARD Flight(Ground Testing Fac. Correlation; 7 p
    Format: text
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  • 67
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    Some aspects on unsteady flow past airfoils and cascades (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The unsteady boundary layer due to a gust propagating past an isolated airfoil and on airfoils in cascade was measured with a hot wire anemometer in a low speed gust tunnel. Coherent signals were obtained by a phase lock averaging technique that was implemented in an on-line analysis using a PDP 12 computer. Changes in a boundary layer shape factor, noise level, and pressure gradient were correlated over a complete gust cycle. It is concluded that the character of the boundary layer changes from laminar to turbulent and back to laminar during the course of a gust cycle at certain chordwise positions. These measurements help explain certain anomalies that were observed during a previous study of the pressure fluctuations due to gust loadings on airfoils and cascades.
    Keywords: AERODYNAMICS
    Type: AGARD Unsteady Phenomena in Turbomachinery; 11 p
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  • 68
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    Comparisons of flight measurements with predictions from aeroelastic models in the NASA Langley Transonic Dynamics Tunnel (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The NASA Langley Transonic Dynamics Tunnel, which has a variable density Freon-12 (or air) test medium, was designed for the study of dynamics and aeroelastic problems of aerospace vehicles. During the 15 years of operation of this facility there have been various opportunities to compare wind tunnel and flight test results. Some of these opportunities arise from routine flight checks of the prototype, others from carefully designed comparative wind tunnel and flight experiments. Data obtained from various sources is presented. The topics covered are: gust and buffet response, control surface effectiveness, flutter, and active control of aeroelastic effects. Some benefits and shortcomings of Freon-12 as a test medium are also discussed. Although areas of uncertainly are evident and there is a continuing need for improvements in model simulation and testing techniques, the results indicate that predictions from aeroelastic model tests are, in general, substantiated by full scale flight tests.
    Keywords: AERODYNAMICS
    Type: AGARD Flight(Ground Testing Fac. Correlation; 9 p
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  • 69
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    Some current research in unsteady aerodynamics: A report from the Fluid Dynamics Panel (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The highlights of a recent discussion by representatives of the fluid dynamics and structures and materials panels are reported with emphasis on the fundamental aspects of unsteady fluid mechanics. Topics include linearized potential flow theory, transonic flow calculations, unsteady boundary layers, dynamic stall, transonic buffet, and techniques for measuring unsteady pressures.
    Keywords: AERODYNAMICS
    Type: AGARD Unsteady Phenomena in Turbomachinery; 13 p
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  • 70
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    Correlation with flight of some aeroelastic model studies in the NASA Langley transonic dynamics tunnel (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The NASA Langley transonic dynamics tunnel, which has a variable density Freon-12 (or air) test medium, was designed specifically for the study of dynamics and aeroelastic problems of aerospace vehicles. During the 15 years of operation of this facility, there have been various opportunities to compare wind tunnel and flight test results. Some of these opportunities arise from routine flight checks of the prototypes; others, from carefully designed comparative wind-tunnel and flight experiments. Such data obtained from various published and unpublished sources are presented. The topics covered are: gust and buffet response, control surface effectiveness, flutter, and active control of aeroelastic effects. Some benefits and shortcomings of Freon-12 as a test medium are also discussed. Although areas of uncertainty are evident and there is a continuing need for improvements in model simulation and testing techniques, the results presented indicate that predictions from aeroelastic model tests are, in general, substantiated by full scale flight tests.
    Keywords: AERODYNAMICS
    Type: Its Flutter Testing Tech.,; p 243-262
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  • 71
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    The design, analysis, and testing of a low-budget wind-tunnel flutter model with active aerodynamic controls (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A low budget flutter model incorporating active aerodynamic controls for flutter suppression studies was designed as both an educational and research tool to study the interfering lifting surface flutter phenomenon in the form of a swept wing-tail configuration. A flutter suppression mechanism was demonstrated on a simple semirigid three-degree-of-freedom flutter model of this configuration employing an active stabilator control, and was then verified analytically using a doublet lattice lifting surface code and the model's measured mass, mode shapes, and frequencies in a flutter analysis. Preliminary studies were significantly encouraging to extend the analysis to the larger degree of freedom AFFDL wing-tail flutter model where additional analytical flutter suppression studies indicated significant gains in flutter margins could be achieved. The analytical and experimental design of a flutter suppression system for the AFFDL model is presented along with the results of a preliminary passive flutter test.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Flutter Testing Tech.,; p 213-242
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  • 72
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    Curve fitting of aeroelastic transient response data with exponential functions (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The extraction of frequency, damping, amplitude, and phase information from unforced transient response data is considered. These quantities are obtained from the parameters determined by fitting the digitized time-history data in a least-squares sense with complex exponential functions. The highlights of the method are described, and the results of several test cases are presented. The effects of noise are considered both by using analytical examples with random noise and by estimating the standard deviation of the parameters from maximum-likelihood theory.
    Keywords: AERODYNAMICS
    Type: Flutter Testing Tech.,; p 43-58
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  • 73
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    Developments in steady and unsteady aerodynamics for use in aeroelastic analysis and design (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A review is given of seven research projects which are aimed at improving the generality, accuracy, and computational efficiency of steady and unsteady aerodynamic theory for use in aeroelastic analysis and design. These projects indicate three major thrusts of current research efforts: (1) more realistic representation of steady and unsteady subsonic and supersonic loads on aircraft configurations of general shape with emphasis on structural-design applications, (2) unsteady aerodynamics for application in active-controls analyses, and (3) unsteady aerodynamics for the frequently critical transonic speed range. The review of each project includes theoretical background, description of capabilities, results of application, current status, and plans for further development and use.
    Keywords: AERODYNAMICS
    Type: Proc. of the SCAR Conf., Pt. 2,; 31 p
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  • 74
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    Upper Surface Nacelle Influence on SCAR Aerodynamic Characteristics at Transonic Speeds (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The arrow-wing transport configuration with detached engines located over the wing to produce upper surface exhaust flow effects was tested at angles of attack from -4 deg to 8 deg and jet total-pressure ratios from 1 (Jet off) to approximately 10. Wing tip leading edge flap deflections of -10 deg to 10 deg were tested with the wing-body configuration only (no nacelles). Tests were made with various nacelle chordwise, spanwise, and vertical height locations over the Mach number, angle of attack, and jet total-pressure ratio ranges. Deflecting the wing tip leading edge flap from 0 deg to -10 deg increased maximum lift to drag ratio by 1.0 at subsonic speeds. Installation of upper surface nacelles (no wing/nacelle pylons) increased the wing-body pitching moment at all Mach numbers and decreased the drag of the wing-body configuration at subsonic Mach numbers. Jet exhaust interference effects were negligible.
    Keywords: AERODYNAMICS
    Type: Proc. of the SCAR Conf., Part 1; p 137-154
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  • 75
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    Results of recent NASA research on low-speed aerodynamic characteristics of supersonic cruise aircraft (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The relatively low values of lift-curve slope produced by highly swept arrow wings, coupled with the low scrape angle of the fuselage, resulted in relatively low values of take-off and approach lift coefficients. Through the use of more efficient high-lift systems and the application of propulsive-lift concepts, it is possible to optimize the engine-airframe design for maximum range potential and also to provide good low-speed performance. Nose strakes provide significant improvements in directional stability characteristics and the use of a propulsive lateral control system provides a solution to problems associated with inherently low levels of lateral control.
    Keywords: AERODYNAMICS
    Type: Proc. of the SCAR Conf., Part 1; p 123-135
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  • 76
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    Development of an aerodyanmic theory capable of predicting surface loads on slender wings with vortex flow (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Boeing Commercial Airplane Company developed an inviscid three-dimensional lifting surface method that shows promise in being able to accurately predict loads, subsonic and supersonic, on wings with leading-edge separation and reattachment.
    Keywords: AERODYNAMICS
    Type: Proc. of the SCAR Conf., Part 1; p 55-68
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  • 77
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    Theoretical and experimental pressure distributions for a 71.2 degree swept arrow-wing configuration at subsonic, transonic, and supersonic speeds (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A wind-tunnel test of an arrow-wing body configuration consisting of flat and twisted wings, as well as a variety of leading- and trailing-edge control-surface deflections, was conducted at Mach numbers from 0.40 to 2.50 to provide an experimental data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions were made using current state-of-the-art and newly developed attached- and separated-flow methods. Conditions were delineated under which these theories provide accurate basic and incremental aeroelastic loads predictions. Current state-of-the-art linear and nonlinear attached-flow methods were adequate only at small-angle-of-attack cruise conditions. Of the several separated-vortex methods evaluated, only the one utilizing a combination of linear source and quadratically varying doublet panels showed promise of yielding accurate loads distributions at moderate to large angles of attack.
    Keywords: AERODYNAMICS
    Type: Proc. of the SCAR Conf., Part 1; p 85-122
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  • 78
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    Advanced Transonic Aerodynamic Technology (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Supercritical airfoils and their applications to wings for various types of aircraft are studied. The various wings discussed were designed for a subsonic jet transport with increased speed, a variable sweep fighter with greater transonic maneuverability, a high subsonic speed STOL jet transport with improved low speed characteristics, and a subsonic jet transport with substantially improved aerodynamic efficiency. Results of wind tunnel and flight demonstration investigations are described. Also discussed are refinements of the transonic area rule concept and methods for reducing the aerodynamic interference between engine nacelles and wings at high subsonic speeds.
    Keywords: AERODYNAMICS
    Type: Advan. in Eng. Sci., Vol. 4; p 1521-1537
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  • 79
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    Separated laminar boundary layers (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Classical boundary layer theory is inadequate to deal with the problem of flow separation owing to its underlying assumption that the boundary layer has an insignificant effect on the external stream. This difficulty is resolved by a theory which includes interaction with the external flow. This theory is described from the viewpoint of the asymptotic triple deck structure. Several triple deck studies are reviewed with emphasis on results of interest in aeronautical applications.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 4; p 1437-1450
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  • 80
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    Three-dimensional boundary layers approaching separation (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The theory of semi-similar solutions of the laminar boundary layer equations is applied to several flows in which the boundary layer approaches a three-dimensional separation line. The solutions obtained are used to deduce the nature of three-dimensional separation. It is shown that in these cases separation is of the "ordinary" type. A solution is also presented for a case in which a vortex is embedded within the three-dimensional boundary layer.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 4; p 1409-1421
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  • 81
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    An application of the suction analog for the analysis of asymmetric flow situations (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A recent extension of the suction analogy for estimation of vortex loads on asymmetric configurations is reviewed. This extension includes asymmetric augmented vortex lift and the forward sweep effect on side edge suction. Application of this extension to a series of skewed wings has resulted in an improved estimating capability for a wide range of asymmetric flow situations. Hence, the suction analogy concept now has more general applicability for subsonic lifting surface analysis.
    Keywords: AERODYNAMICS
    Type: Advan. in Eng. Sci., Vol. 4; p 1331-1347
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  • 82
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    Improved computational treatment of transonic flow about swept wings (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Relaxation solutions to classical three-dimensional small-disturbance (CSD) theory for transonic flow about lifting swept wings are reported. For such wings, the CSD theory was found to be a poor approximation to the full potential equation in regions of the flow field that are essentially two-dimensional in a plane normal to the sweep direction. The effect of this deficiency on the capture of embedded shock waves in terms of (1) the conditions under which shock waves can exist and (2) the relations they must satisfy when they do exist is emphasized. A modified small-disturbance (MSD) equation, derived by retaining two previously neglected terms, was proposed and shown to be a consistent approximation to the full potential equation over a wider range of sweep angles. The effect of these extra terms is demonstrated by comparing CSD, MSD, and experimental wing surface pressures.
    Keywords: AERODYNAMICS
    Type: Advan. in Eng. Sci., Vol. 4; p 1311-1320
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  • 83
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    Application of the nonlinear vortex-lattice concept to aircraft-interference problems (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A discrete-vortex model was developed to account for the hazardous effects of the vortex trail issued from the edges of separation of a large leading wing on a small trailing wing. The model is divided into three main parts: the leading wing and its near wake, the near and far wakes of the leading wing, and the trailing wing and the portion of the far wake in its vicinity. The normal force, pitching moment, and rolling moment coefficients for the trailing wing are calculated. The circulation distribution in the vortex trail is calculated in the first part of the model where the leading wing is far upstream and hence is considered isolated. A numerical example is solved to demonstrate the feasibility of using this method to study interference between aircraft. The numerical results show the correct trends: The following wing experiences a loss in lift between the wing-tip vortex systems of the leading wing, a gain outside this region, and strong rolling moments which can change sign as the lateral relative position changes. All the results are strongly dependent on the vertical relative position.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 4; p 1321-1330
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  • 84
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    Sample wings for study (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Two simple wings were selected for study using the various implementations (old and new) of the vortex lattice method. These are: (1) a rectangular wing with an aspect ratio of 2, and (2) a tapered wing with an aspect ratio of 5, a taper ratio of 0.5, a leading sweep of 3.317 deg., and a trailing edge sweep of 1-11.308 deg. This was done in order to gain an appreciation for the accuracy of the various implementations. References were given where force, moment, and pressure data could be found for these wings.
    Keywords: AERODYNAMICS
    Type: Vortex-Lattice Utilization; p 423-424
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  • 85
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    Unsteady flow past wings having sharp-edge separation (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A vortex-lattice technique is developed to model unsteady, incompressible flow past thin wings. This technique predicts the shape of the wake as a function of time; thus, it is not restricted by planform, aspect ratio, or angle of attack as long as vortex bursting does not occur and the flow does not separate from the wing surface. Moreover, the technique can be applied to wings of arbitrary curvature undergoing general motion; thus, it can treat rigid-body motion, arbitrary wing deformation, gusts in the freestream, and periodic motions. Numerical results are presented for low-aspect rectangular wings undergoing a constant-rate, rigid-body rotation about the trailing edge. The results for the unsteady motion are compared with those predicted by assuming quasi-steady motion. The present results exhibit hysteretic behavior.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 407-421
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  • 86
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    A subvortex technique for the close approach to a discretized vortex sheet (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The close-approach problem associated with vortex-lattice methods was examined numerically with the objective of calculating velocities at arbitrary points, not just at midpoints, between the vortices. The objective was achieved using a subvortex technique in which a vortex splits into an increasing number of subvortices as it is approached. The technique, incorporated in a two-dimensional potential flow method using "submerged" vortices and sources, was evaluated for a cambered Joukowski airfoil. The method could be extended to three dimensions, and should improve non-linear methods, which calculate interference effects between multiple wings and vortex wakes, and which include procedures for force-free wakes.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 369-384
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  • 87
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    Some applications of the quasi vortex-lattice method in steady and unsteady aerodynamics (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The quasi vortex-lattice method is reviewed and applied to the evaluation of backwash, with applications to ground effect analysis. It is also extended to unsteady aerodynamics, with particular interest in the calculation of unsteady leading-edge suction. Some applications in ornithopter aerodynamics are given.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 385-406
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  • 88
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    Comparison of vortex lattice predicted forces with wind tunnel experiments for the F-4E(CCV) airplane with a closely coupled canard (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The F-4E (CCV) wind tunnel model with closely coupled canard control surfaces was analyzed by means of a version of a vortex lattice program that included the effects of nonlinear leading edge or side edge vortex lift on as many as four individual planforms. The results were compared with experimental data from wind tunnel tests of a 5% scale model tested at a Mach number M = 0.6. They indicated that a nonlinear vortex lift developed on the side edges due to tip vortices, but did not appear to develop on the leading edges within the range of angles of attack that were studied. Instead, substantial leading edge thrust was developed on the lifting surfaces. A configuration buildup illustrated the mutual interference between the wing and control surfaces. On the configuration studied, addition of the wing increased the loading on the canard, but the additional load on the canard due to adding the stabilator was small.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 261-283
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  • 89
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    Some recent applications of the suction analogy to asymmetric flow situations (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A recent extension of the suction analogy for the estimation of vortex loads on asymmetric configurations was reviewed. This includes the asymmetric augmented vortex lift and the forward sweep effect on side edge suction. Application of this extension to a series of skewed wings has resulted in an improved estimating capability for a wide range of asymmetric flow situations. Hence, the suction analogy concept now has more general applicability for subsonic lifting surface analysis.
    Keywords: AERODYNAMICS
    Type: Vortex-Lattice Utilization; p 219-236
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  • 90
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    A quadrilateral vortex method applied to configurations with high circulation (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A quadrilateral vortex-lattice method is briefly described for calculating the potential flow aerodynamic characteristics of high-lift configurations. It incorporates an iterative scheme for calculating the deformation of forcefree wakes, including wakes from side edges. The method is applicable to multiple lifting surfaces with part-span flaps deflected, and can include ground effect and wind-tunnel interference. Numerical results, presented for a number of high-lift configurations, demonstrate rapid convergence of the iterative technique. The results are in good agreement with available experimental data.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 163-186
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  • 91
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    Application of the vortex-lattice technique to the analysis of thin wings with vortex separation and thick multi-element wings (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two techniques for extending the range of applicability of the basic vortex-lattice method are discussed. The first improves the computation of aerodynamic forces on thin, low-aspect-ratio wings of arbitrary planforms at subsonic Mach numbers by including the effects of leading-edge and tip vortex separation, characteristic of this type wing, through use of the well-known suction-analogy method of E. C. Polhamus. Comparisons with experimental data for a variety of planforms are presented. The second consists of the use of the vortex-lattice method to predict pressure distributions over thick multi-element wings (wings with leading- and trailing-edge devices). A method of laying out the lattice is described which gives accurate pressures on the top and part of the bottom surface of the wing. Limited comparisons between the result predicted by this method, the conventional lattice arrangement method, experimental data, and 2-D potential flow analysis techniques are presented.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 237-260
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  • 92
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    Utilization of the AEDC three-dimensional potential flow computer program (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A potential flow computer program which has been in use for several years, was discussed. This program has been used primarily as a tool for flow-field analysis in support of test activities in transonic wind tunnels. Analyses have been made over a Mach number range from 0 to 0.9 for a variety of configurations from aircraft to wind tunnels, with excellent agreement between calculated flow fields and measured wind tunnel data. Analytical and experimental data for seven different flow analysis problems are presented in this paper.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 127-143
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  • 93
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    Applications of vortex lattice theory to preliminary aerodynamic design (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Some applications of the vortex-lattice theory to the preliminary aerodynamic design and analysis of subsonic aircraft were presented. These methods include the Rockwell-Tulinius vortex-lattice theory for estimating aerodynamic characteristics, a Trefftz plane optimization procedure for determining the span loads for minimum induced drag, and a modification of the Trefftz plane procedure to estimate the induced drag for specified span loads. The first two methods are used to aerodynamically design aircraft planforms, twists, and cambers, and the latter method is used to estimate the drag for components such as flaps and control surfaces. Results from the theories for predicting lift and pitching moment, drag due to lift, and the drag of control surfaces are compared with experimental data. This data was obtained on a general aviation model with flaps and a close-coupled canard-wing model.
    Keywords: AERODYNAMICS
    Type: Vortex-Lattice Utilization; p 113-126
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  • 94
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    Minimum trim drag design for interfering lifting surfaces using vortex-lattice methodology (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A new method has been developed by which the mean camber surface can be determined for trimmed noncoplanar planforms with minimum vortex drag under subsonic conditions. The method uses a vortex lattice and overcomes previous difficulties with chord loading specification; it uses a Trefftz plane analysis to determine the optimum span loading for minimum drag, then solves for the mean camber surface of the wing which will provide the required loading. Pitching-moment or root-bending-moment constraints can be employed as well at the design lift coefficient. Sensitivity studies of vortex-lattice arrangement have been made with this method and are presented. Comparisons with other theories show generally good agreement. The versatility of the method is demonstrated by applying it to (1) isolated wings, (2) wing-canard configurations, (3) a tandem wing, and (4) a wing-winglet configuration.
    Keywords: AERODYNAMICS
    Type: Vortex-Lattice Utilization; p 89-111
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  • 95
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    Numerical method to calculate the induced drag or optimum loading for arbitrary non-planar aircraft (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A simple unified numerical method applicable to non-planar subsonic aircraft has been developed for calculating either the induced drag for an arbitrary loading or the optimum aircraft loading which results in minimum induced drag. The method utilizes a vortex lattice representation of the aircraft lifting surfaces coupled with the classic equations and theorems for computing and minimizing induced drag. Correlation of results from the numerical method with non-planar solutions obtained from other more complex theories indicates very good agreement. Comparison of the induced-drag computations using the numerical method with experimental data for planar and non-planar configurations was also very good.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 49-70
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  • 96
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    Extended applications of the vortex lattice method (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The application of the vortex lattice method to problems not usually dealt with by this technique is considered. It is shown that if the discrete vortex lattice is considered as an approximation to surface-distributed vorticity, then the concept of the generalized principal part of an integral yields a residual term to the vortex-induced velocity that renders the vortex lattice method valid for supersonic flow. Special schemes for simulating non-zero thickness lifting surfaces and fusiform bodies with vortex lattice elements are presented. Thickness effects of wing-like components are simulated by a double vortex lattice layer, and fusiform bodies are represented by a vortex grid arranged on a series of concentric cylindrical surfaces. Numerical considerations peculiar to the application of these techniques are briefly discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 27-47
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  • 97
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    Subsonic finite elements for wing body combinations (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Capabilities, limitations, and applications of various theories for the prediction of wing-body aerodynamics are reviewed. The methods range from approximate planar representations applicable in preliminary design to surface singularity approaches applicable in the later stages of detail design. The available methods for three-dimensional configurations are limited as inviscid solutions with viscous effects included on an empirical or strip basis.
    Keywords: AERODYNAMICS
    Type: Vortex-Lattice Utilization; p 11-26
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  • 98
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    Historical evolution of vortex-lattice methods (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A review of the beginning and some orientation of the vortex-lattice method were given. The historical course of this method was followed in conjunction with its field of computational fluid dynamics, spanning the period from L.F. Richardson's paper in 1910 to 1975. The following landmarks were pointed out: numerical analysis of partial differential equations, lifting-line theory, finite-difference method, 1/4-3/4 rule, block relaxation technique, application of electronic computers, and advanced panel methods.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 1-9
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  • 99
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    Optimization and design of three-dimensional aerodynamic configurations of arbitrary shape by a vortex lattice method (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A new method based on vortex lattice theory has been developed which can be applied to the combined analysis, induced drag optimization, and aerodynamic design of three-dimensional configurations of arbitrary shape. Geometric and aerodynamic constraints can be imposed on both the optimization and the design process. The method is compared with several known analytical solutions and is applied to several different design and optimization problems, including formation flight and wingtip fins for the Boeing KC-135 tanker airplane. Good agreement has been observed between the theoretical predictions and the wind tunnel test results for the KC-135 modification.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 71-88
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  • 100
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    Laser velocimetry applied to transonic and supersonic aerodynamics (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: As a further demonstration of the capabilities of laser velocity in compressible aerodynamics, measurements obtained in a Mach 2.9 separated turbulent boundary layer and in the transonic flow past a two-dimensional airfoil section are presented and compared to data realized by conventional techniques. In the separated-flow study, the comparisons were made against pitot-static pressure data. Agreement in mean velocities was realized where the pressure measurements could be considered reliable; however, in regions of instantaneous reverse velocities, the laser results were found to be consistent with the physics of the flow whereas the pressure data were not. The laser data obtained in regions of extremely high turbulence suggest that velocity biasing does not occur if the particle occurrence rate is low relative to the turbulent fluctuation rate. Streamwise turbulence intensities are also presented. In the transonic airfoil study, velocity measurements obtained immediately outside the upper surface boundary layer of a 6-inch chord MACA 64A010 airfoil are compared to edge velocities inferred from surface pressure measurements. For free-stream Mach numbers of 0.6 and 0.8, the agreement in results was very good. Dual scatter optical arrangements in conjunction with a single particle, counter-type signal processor were employed in these investigations. Half-micron-diameter polystyrene spheres and naturally occurring condensed oil vapor acted as light scatterers in the two respective flows. Bragg-cell frequency shifting was utilized in the separated flow study.
    Keywords: AERODYNAMICS
    Type: AGARD Appl. of Non-Intrusive Instr. in Fluid Flow Res.; 12 p
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