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  • 1
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    Turbulence modeling of shock separated boundary-layer flows (1977)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: Computations of transonic and hypersonic shock-separated boundary-layer flows using zero-equation (algebraic), one-equation (kinetic energy), and two-equation (kinetic energy plus length scale) turbulence eddy viscosity models are described and compared with measurements. The computations make use of a new Navier-Stokes computer algorithm that has reduced computing times by one to two orders of magnitude. The algorithm, and how the turbulence models are incorporated into it, are described. Results for the transonic flow show that the unmodified one-equation model is superior to the zero-equation model in skin-friction predictions. For the hypersonic flow, a highly modified one-equation model that accurately predicts surface pressure and heat transfer is described. Preliminary two-equation model results are also presented.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Apr 18, 1977 - Apr 20, 1977; University Park, PA
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  • 2
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    Computation of unsteady transonic flows by the indicial method (1977)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The indicial method is investigated for the computation of unsteady transonic force and moment coefficients for use in flutter analyses. This approach has the advantage that solutions for all reduced frequencies for a given mode of motion can be obtained from a single finite-difference flowfield computation. Comparisons of indicial and time-integration computations for oscillating airfoil and flap motions help define limits on the motion amplitude for the applicability of the indicial method to transonic flows. Within these limits, solutions for various motion modes can be superposed to obtain solutions for multiple-degree-of-freedom aeroelastic systems. Also, a simple aeroelastic problem is solved by an alternative approach in which the structural motion and flowfield equations are integrated simultaneously using a time-integration finite-difference procedure.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-447 , Mar 24, 1977 - Mar 25, 1977|Conference on Structures, Structural Dynamics and Materials; Mar 21, 1977 - Mar 23, 1977; San Diego, CA; US
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  • 3
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    Flutter analysis of a glider made of synthetic materials (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A description of the flutter behavior of the Standard Cirrus is given. Steady vibration tests were conducted, and vibration and flutter calculations were made.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75160
    Format: application/pdf
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  • 4
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    A survey of computational aerodynamics in the United States (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Programs in theoretical and computational aerodynamics in the United States are described. Those aspects of programs that relate to aeronautics are detailed. The role of analysis at various levels of sophistication is discussed as well as the inverse solution techniques that are of primary importance in design methodology. The research is divided into the broad categories of application for boundary layer flow, Navier-Stokes turbulence modeling, internal flows, two-dimensional configurations, subsonic and supersonic aircraft, transonic aircraft, and the space shuttle. A survey of representative work in each area is presented.
    Keywords: AERODYNAMICS
    Type: NASA-SP-394
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  • 5
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    Wake Vortex Minimization (1977)
    In:  CASI
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    Publication Date: 2019-08-28
    Description: A status report is presented on research directed at reducing the vortex disturbances of aircraft wakes. The objective of such a reduction is to minimize the hazard to smaller aircraft that might encounter these wakes. Inviscid modeling was used to study trailing vortices and viscous effects were investigated. Laser velocimeters were utilized in the measurement of aircraft wakes. Flight and wind tunnel tests were performed on scale and full model scale aircraft of various design. Parameters investigated included the effect of wing span, wing flaps, spoilers, splines and engine thrust on vortex attenuation. Results indicate that vortives may be alleviated through aerodynamic means.
    Keywords: AERODYNAMICS
    Type: NASA-SP-409 , Feb 25, 1976 - Feb 26, 1976; Washington
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  • 6
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    Aerodynamic Characteristics at Mach Numbers from 0.6 to 2.16 of a Supersonic Cruise Fighter Configuration with a Design Mach Number of 1.8 (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: An investigation was made in the Langley 8-foot transonic tunnel and the Langley Unitary Plan wind tunnel, over a Mach number range of 0.6 to 2.16, to determine the static longitudinal and lateral aerodynamic characteristics of a model of a supersonic-cruise fighter. The configuration, which is designed for efficient cruise at Mach number 1.8, is a twin-engine tailless arrow-wing concept with a single rectangular inlet beneath the fuselage and outboard vertical tails and ventral fins. It had untrimmed values of lift-drage ratio ranging from 10 at subsonic speeds to 6.4 at the design Mach number. The configuration was statically stable both longitudinally and laterally.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-3559 , L-11604
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  • 7
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    Investigation of Inlet Concepts for Maneuver Improvement at Transonic Speeds (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: A 15 percent scale lightweight fighter type inlet forebody was tested in the Ames 14 foot transonic wind tunnel at Mach numbers of 0.7, 0.9, and 1.04. The inlet was a two dimensional horizontal ramp system designed for a Mach number of 2.2. Four inlet devices designed to prevent or delay cowl-lip boundary layer separation or to improve the inlet internal flow characteristics at high angles of attack were investigated. The devices used to control cowl-lip separation consisted of cowl leading edge flaps, slotted flaps, and tangential blowing. To improve the internal flow characteristics, discrete jet nozzle flows were directed downstream and parallel to the duct surface in the subsonic diffuser to energize the wall boundary layer. The discrete jets used in the subsonic diffuser were also tested in combination with each of the cowl leading edge devices. Test measurements included engine-face total pressure recovery, steady state distortion, dynamic distortion, duct boundary layer profiles, and duct-surface static pressures.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-73215 , A-6952
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  • 8
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    Instability of a compressible circular free jet with consideration of the influence of the jet boundary layer thickness (1977)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: The instability of a circular jet was investigated by means of the inviscid linearized stability theory. By variation of a jet parameter which takes the ratio of jet radius to boundary layer thickness into account, the influence of axisymmetry on the spatial growth rate and disturbance phase velocity is studied. The influence of Mach number and temperature ratio is discussed. A comparison with measurements shows that the instability of a turbulent jet boundary layer may also be explained by these results.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75190
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  • 9
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    Effect of flap deflection on the lift coefficient of wings operating in a biplane configuration (1977)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: Biplane models with a lift flap were tested in a wind tunnel to study the effect of flap deflection on the aerodynamic coefficient of the biplane as well as of the individual wings. Optimization of the position flap was carried out, and the effect of changes in the chord length of the lower wing was determined for the aerodynamic structure of a biplane with a lift flap on the upper wing.
    Keywords: AERODYNAMICS
    Type: NASA-TM-75059
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  • 10
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    Small disturbances in a compressor with strong swirl (1977)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: A detailed time resolved study of the flow field upstream and downstream of a high work transonic compressor rotor shows that the flow field is dominated by the downstream evolution of the viscous flow shed from the rotor blades under the influence of the strong mean swirl. The dominant periodicity in the flow changes from blade passing to 1.4 times blade passing within one chord from the blade row. A possible explanation is that the wakes evolve to a shear eigenmode of the swirling flow, as suggested by perturbation theory. Another possibility is a 'propagating stall' of 16 cells, but the rotor operated near its design point. Treatments of 'turbulence' in turbomachines should account for such phenomena, which originate in the strong mean swirl.
    Keywords: AERODYNAMICS
    Type: SQUID Workshop; 15, 1976; Warrenton, VA
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  • 11
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    Unsteady transonic flow computations (1977)
    In:  Other Sources
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    Publication Date: 2019-07-27
    Description: The numerical procedures previously developed for computing nonlinear and time-linearized small-perturbation unsteady transonic flows are briefly reviewed, and the effects of unsteady modes of motion on two-dimensional transonic flows are evaluated. The numerical procedure used comprises an alternating-direction implicit scheme and treats shock waves as discontinuities in the flow. Comparison of the time-linearized results with fully nonlinear calculations delineates their range of applicability. The unsteady behavior due to harmonic pitching and flap oscillations of an NACA airfoil is also examined.
    Keywords: AERODYNAMICS
    Type: Symposium on Unsteady Aerodynamics; Sept. 26-28, 1977; Ottawa; Canada
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  • 12
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    On the prediction of viscous phenomena in transonic flows (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An algorithm developed by MacCormack (1971) and applied to transonic flows by Deiwert (1974) is used in the reported investigation. The investigation is concerned with flows of aerodynamic interest. However, many of the concepts apply equally to flows in turbomachinery. Turbulent transonic flows are considered, taking into account a biconvex circular arc and a shockless lifting airfoil. A simple algebraic eddy viscosity model is used for the description of the turbulent transport process.
    Keywords: AERODYNAMICS
    Type: Transonic flow problems in turbomachinery; Feb 11, 1976 - Feb 12, 1976; Monterey, CA
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  • 13
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    Supercritical cascade design (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The use of the method of complex extension to achieve better aerodynamic designs for supercritical cascades applicable to transonic turbomachinery is discussed. The method permits the computation of analytical solutions to elliptic, hyperbolic or mixed second-order partial equations in two dimensions. Boundary value problems formulated to develop an airfoil shape having a prescribed speed distribution for subsonic flow and a nearby speed distribution in the transonic case are also considered. Computing times necessary to run the blade design program are described as acceptably short.
    Keywords: AERODYNAMICS
    Type: Transonic flow problems in turbomachinery; Feb 11, 1976 - Feb 12, 1976; Monterey, CA
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  • 14
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    Calculation of 3-dimensional choking mass flow in turbomachinery with 2-dimensional flow models (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An approach is considered for obtaining an approximate flow solution in the case of a cross-sectional flow surface within a guided channel, taking into account a pair of typical turbine blades with three-dimensional orthogonal surfaces across the flow passage, the calculation of the mass flow across the throat in the case of a 2-D passage with curved walls, and the determination of the choking mass flow. It is pointed out that the choking solution for a three-dimensional guided passage in a blade row can be obtained in a very similar manner by satisfying momentum equations for the blade-to-blade and the hub-to-tip direction. A considered example involves the calculation of the choking mass flow for a centrifugal compressor impeller in an automotive application.
    Keywords: AERODYNAMICS
    Type: Transonic flow problems in turbomachinery; Feb 11, 1976 - Feb 12, 1976; Monterey, CA
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  • 15
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    Aerodynamic characteristics of airplanes at high angles of attack (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: An introduction to, and a broad overiew of, the aerodynamic characteristics of airplanes at high angles of attack are provided. Items include: (1) some important fundamental phenomena which determine the aerodynamic characteristics of airplanes at high angles of attack; (2) static and dynamic aerodynamic characteristics near the stall; (3) aerodynamics of the spin; (4) test techniques used in stall/spin studies; (5) applications of aerodynamic data to problems in flight dynamics in the stall/spin area; and (6) the outlook for future research in the area. Although stalling and spinning are flight dynamic problems of importance to all aircraft, including general aviation aircraft, commercial transports, and military airplanes, emphasis is placed on military configurations and the principle aerodynamic factors which influence the stability and control of such vehicles at high angles of attack.
    Keywords: AERODYNAMICS
    Type: NASA-TM-74097 , L-11695 , AGARD/VKI Lecture Series on Aerodynamic Inputs for Problems in Aircraft Dynamics; Apr 25, 1977 - Apr 29, 1977; Rhode-St-Genese; Belgium
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  • 16
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    Aerodynamic interference effects on tilting proprotor aircraft (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The Green's function method was used to study tilting proprotor aircraft aerodynamics with particular application to the problem of the mutual interference of the wing-fuselage-tail-rotor wake configuration. While the formulation is valid for fully unsteady rotor aerodynamics, attention was directed to steady state aerodynamics, which was achieved by replacing the rotor with the actuator disk approximation. The use of an actuator disk analysis introduced a mathematical singularity into the formulation; this problem was studied and resolved. The pressure distribution, lift, and pitching moment were obtained for an XV-15 wing-fuselage-tail rotor configuration at various flight conditions. For the flight configurations explored, the effects of the rotor wake interference on the XV-15 tilt rotor aircraft yielded a reduction in the total lift and an increase in the nose-down pitching moment. This method provides an analytical capability that is simple to apply and can be used to investigate fuselage-tail rotor wake interference as well as to explore other rotor design problem areas.
    Keywords: AERODYNAMICS
    Type: NASA-CR-152053 , ASI-TR-76-28
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  • 17
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    Models and techniques for evaluating the effectiveness of aircraft computing systems (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Models, measures and techniques were developed for evaluating the effectiveness of aircraft computing systems. The concept of effectiveness involves aspects of system performance, reliability and worth. Specifically done was a detailed development of model hierarchy at mission, functional task, and computational task levels. An appropriate class of stochastic models was investigated which served as bottom level models in the hierarchial scheme. A unified measure of effectiveness called 'performability' was defined and formulated.
    Keywords: AERODYNAMICS
    Type: NASA-CR-145270 , SEL-111 , SASR-2
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  • 18
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    Sonic boom analysis for high-altitude flight at high Mach number (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Numerical programs for the computation of the flow field from the airplane at the flight altitude to the ground are presented. They take into account the nonlinear effects of high Mach number, the entropy change across the shock, the entropy and enthalpy variations in the atmospheric layer, and the gravitational effect. Extension of the programs for the axisymmetric problems to handle nonaxisymmetric terms is described. The asymmetry can be caused by the geometry of the body and the lift, and also by the fact that the variations in the atmospheric layer are two-dimensional. Numerical results for ground level signatures of several configurations at various flight conditions are presented and compared with existing approximate theories to demonstrate the influences of these nonlinear effects.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 73-1034 , Selected Papers on Advanced Design of Air Vehicles; p 65-74|AIAA Aero-Acoustics Conf.; Oct 15, 1973 - Oct 17, 1973; Seattle
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  • 19
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    Forward speed effects on blown flap noise (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The effects of forward speed on the noise of under-the-wing (externally blown flaps, EBF) and over-the-wing (upper surface blown, USB) blown flap configurations were measured in wind tunnel model tests with cold jets. The results are presented without correction for the effects (e.g., signal convection, shear layer refraction) associated with flight simulation in a wind tunnel or free jet facility. Noise decreases were generally observed at microphones forward of the wing. The reductions were larger at the low frequencies (below peak SPL) than at the high (above peak SPL). Noise increases of 10 dB or more were observed at the aft microphones, especially in the high frequency range.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-1315 , Aeroacoustics Conference; Oct 03, 1977 - Oct 05, 1977; Atlanta, GA
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  • 20
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    Unsteady aerodynamic modeling for arbitrary motions (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A study is presented on the unsteady aerodynamic loads due to arbitrary motions of a thin wing and their adaptation for the calculation of response and true stability of aeroelastic modes. In an Appendix, the use of Laplace transform techniques and the generalized Theodorsen function for two-dimensional incompressible flow is reviewed. New applications of the same approach are shown also to yield airloads valid for quite general small motions. Numerical results are given for the two-dimensional supersonic case. Previously proposed approximate methods, starting from simple harmonic unsteady theory, are evaluated by comparison with exact results obtained by the present approach. The Laplace inversion integral is employed to separate the loads into 'rational' and 'nonrational' parts, of which only the former are involved in aeroelastic stability of the wing. Among other suggestions for further work, it is explained how existing aerodynamic computer programs may be adapted in a fairly straightforward fashion to deal with arbitrary transients.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-451 , Conference on Structures, Structural Dynamics and Materials; Mar 24, 1977 - Mar 25, 1977; San Diego, CA; United States
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  • 21
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    A subsonic flow investigation on a research body at high angles of attack (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Tests conducted in the Ames 12-foot pressure wind tunnel on a rotating research body at angles of attack of 45 to 90 deg yielded results that were inconsistent with simple cross-flow theory. Consequently, force and pressure distribution tests along with oil and sublimation flow-visualization studies were conducted in the same tunnel on a nonrotating model to attempt to explain the behavior observed in the rotary tests. These studies indicate that at appropriate conditions of Reynolds number and angle of attack, inflectional instabilities occur in the boundary layer that materially affect separation and, hence, the aerodynamic forces. Calculations of cross-flow Reynolds numbers are made and compared with other works on inflectional instability.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-180 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 22
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    Scramjet exhaust simulation technique for hypersonic aircraft nozzle design and aerodynamic tests (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Current design philosophy for scramjet-powered hypersonic aircraft results in configurations with the entire lower fuselage surface utilized as part of the propulsion system. The lower aft-end of the vehicle acts as a high expansion ratio nozzle. Not only must the external nozzle be designed to extract the maximum possible thrust force from the high energy flow at the combustor exit, but the forces produced by the nozzle must be aligned such that they do not unduly affect aerodynamic balance. The strong coupling between the propulsion system and aerodynamics of the aircraft makes imperative at least a partial simulation of the inlet, exhaust, and external flows of the hydrogen-burning scramjet in conventional facilities for both nozzle formulation and aerodynamic-force data acquisition. Aerodynamic testing methods offer no contemporary approach for such vehicle design requirements. NASA-Langley has pursued an extensive scramjet/airframe integration R&D program for several years and has recently developed a promising technique for simulation of the scramjet exhaust flow for hypersonic aircraft. Current results of the research program to develop a scramjet flow simulation technique through the use of substitute gas blends are described in this paper.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-82 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 23
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    Merging of aircraft trailing vortices (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A merging-distance criterion for equal-strength corotational vortices is derived from low-turbulence wind-tunnel flow-visualization data. The vortex separation distance is normalized by defining a vortex core diameter based on circulation defect and angular-momentum defect. Merging may take place for larger separation distances than predicted from earlier two-dimensional inviscid calculations, which indicates that viscosity and possibly three-dimensional effects are important factors in the merging phenomenon. Hot-wire velocity distributions and rolling-moment measurements show that attenuation of the vortex hazard is associated with vortex merging.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-8 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 24
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    Ground-based measurements of the wake vortex characteristics of a B747 aircraft in various configurations (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A Boeing 747 aircraft flew 54 passes at low level over ground-based sensors. Vortex velocities were measured by a laser-Doppler velocimeter, an array of monostatic acoustic sounders, and an array of propeller anemometers. Flow visualization of the wake was achieved using smoke and balloon tracers. Preliminary results were obtained on the initial downwash field, the time for merging of the multiple vortices, the velocity fields, vortex decay, and the effects of spoilers and differential flap settings on the dissipation and structure of vortices.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-9 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 25
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    Reynolds number effects on shock-wave turbulent boundary-layer interactions - A comparison of numerical and experimental results (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An experiment is described that tests and guides computations of a shock-wave turbulent boundary-layer interaction flow over a 20-deg compression corner at Mach 2.85. Numerical solutions of the time-averaged Navier-Stokes equations for the entire flow field, employing various turbulence models, are compared with the data. Each model is critically evaluated by comparisons with the details of the experimental data. Experimental results for the extent of upstream pressure influence and separation location are compared with numerical predictions for a wide range of Reynolds numbers and shock-wave strengths.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-42 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 26
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    Wind-tunnel and flight evaluation of spoilers as trailing-vortex hazard alleviation devices (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper presents the results of ground-based and flight investigations that have been performed at NASA for the purpose of development of spoilers as trailing-vortex hazard alleviation devices. Based on the results obtained in these investigations, it was found that the induced rolling moment on a trailing model can be reduced by spoilers located near the mid-semispan of a vortex-generating wing. Substantial reductions in induced rolling moment occur when the spoiler vortex attenuator is located well forward on both unswept and swept wing models. In addition, it was found by ground-based model tests and verified by full-scale flight tests that the existing flight spoilers on the B-747 aircraft are effective as trailing vortex attenuators. Based on the results of wind-tunnel investigations of the DC-10-30 and L-1011 aircraft models, the existing flight spoilers on both the DC-10-30 and L-1011 aircraft may also be effective trailing vortex attenuators.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-10 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 27
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    Vorticity interaction effects on blunt bodies (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Numerical solutions of the viscous shock layer equations governing laminar and turbulent flows of a perfect gas and radiating and nonradiating mixtures of perfect gases in chemical equilibrium are presented for hypersonic flow over spherically blunted cones and hyperboloids. Turbulent properties are described in terms of the classical mixing length. Results are compared with boundary layer and inviscid flowfield solutions; agreement with inviscid flowfield data is satisfactory. Agreement with boundary layer solutions is good except in regions of strong vorticity interaction; in these flow regions, the viscous shock layer solutions appear to be more satisfactory than the boundary layer solutions. Boundary conditions suitable for hypersonic viscous shock layers are devised for an advanced turbulence theory.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2778 , DCW-R-08-01
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  • 28
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    Estimate of conjugate gamma and gamma prime compositions in Ni-base superalloys (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Approaches for estimating the composition of the matrix phase of alloys from the melt composition are reviewed. The first method is based on assigning essentially fixed stoichiometry to precipitating phases and is typified by PHACOMP. The second method uses analytical geometry to interpret phase diagrams and is applicable to a two-phase region of a six-component Ni-base system. The geometric method is also applicable to commercial Ni-base superalloys.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-73576 , E-9033 , Workshop on Applications of Phase Diagrams in Metallurgy and Ceramics; Jan 10, 1977 - Jan 12, 1977; Gaithersburg, MD; United States
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  • 29
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    Inlet total pressure loss due to acoustic wall treatment (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The effect of diffuser wall acoustic treatment on inlet total pressure loss was experimentally determined. Data were obtained by testing an inlet model with 10 different acoustically treated diffusers differing only in the design of the Helmholtz resonator acoustic treatment. Tests were conducted in a wind tunnel at forward velocities to 41 meters per second for inlet throat Mach numbers of .5 to .8 and angles of attack as high as 50 degrees. Results indicate a pressure loss penalty due to acoustic treatment that increases linearly with the porosity of the acoustic facing sheet. For a surface porosity of 14 percent the total pressure loss was 21 percent greater than that for an untreated inlet.
    Keywords: AERODYNAMICS
    Type: NASA-TM-X-73559 , E-8946 , Aerospace Sci. Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles
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    Unsteady subsonic and supersonic potential aerodynamics for complex configurations (1977)
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    Publication Date: 2019-07-13
    Description: A recently developed general theory for unsteady compressible potential fluid dynamics for complex-configuration aircraft is reviewed. The method is based on a combination of the following techniques: Green's function method (to transform the differential equation into an integral differential-delay equation), finite element method (to transform the equation into a set of differential-delay equations in time), and the Laplace transform method (to transform the differential-delay equations into algebraic equations).
    Keywords: AERODYNAMICS
    Type: International Symposium on Innovative Numerical Analysis in Applied Engineering Science; May 23, 1977 - May 27, 1977; Versailles; France
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    Computer simulation of hypersonic flow over the Space Shuttle Orbiter (1977)
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    Publication Date: 2019-07-13
    Description: Computer simulations of the flow field around the Space Shuttle Orbiter are described. Results of inviscid calculations are presented for the shock wave pattern and bottom centerline pressure distribution at 30 deg angle of attack. Results of viscous calculations are presented for wall pressure and heat transfer distributions for simple configurations representative of regions where shock wave-boundary layer interactions occur. The computer codes are verified by comparisons with wind-tunnel data and can be applied to flight conditions.
    Keywords: AERODYNAMICS
    Type: International Symposium on Space Technology and Science; May 16, 1977 - May 20, 1977; Tokyo; Japan
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    Displacement thickness distributions in transonic flows about 3-D wings (1977)
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    Publication Date: 2019-07-13
    Description: The transonic 3-D inviscid small-perturbation solution of Bailey and Ballhaus is combined with a finite-difference solution for Prandtl's boundary-layer equations in order to include viscous effects. The inviscid-viscous interaction is modeled by means of the displacement surface, which can be thought of as the effective body surface seen by the inviscid flow. Displacement thickness, lift, and pressure distributions resulting from the combined solution are presented for transonic flows about the RAE 101 A wing and a Lockheed transport wing, both at small angles of attack. The influence of changing arbitrarily the start of transition on the displacement surface and lift is discussed for the RAE wing flow.
    Keywords: AERODYNAMICS
    Type: Conference on Numerical Methods in Fluid Mechanics; Oct 11, 1977 - Oct 13, 1977; Cologne; Germany
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    Application of a multi-level grid method to transonic flow calculations (1977)
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    Publication Date: 2019-07-13
    Description: A multi-level grid method has been studied as a possible means of accelerating convergence in relaxation calculations for transonic flows. The method employs a hierarchy of grids, ranging from very coarse (e.g., 8 x 2 mesh cells) to fine (e.g., 128 x 32); the coarser grids are used to diminish the magnitude of the smooth part of the residuals, hopefully with far less total work than would be required with, say, optimal SLOR iterations on the finest grid. The method was applied to the solution of the transonic small-disturbance equation for the velocity potential in the conservation form. Nonlifting transonic flow past a parabolic-arc airfoil is the example studied, with meshes of both constant and variable step size.
    Keywords: AERODYNAMICS
    Type: Transonic flow problems in turbomachinery; Feb 11, 1976 - Feb 12, 1976; Monterey, CA
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    Effects of external stores on the air combat capability of a delta wing fighter (1977)
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    Publication Date: 2019-07-13
    Description: Delta wing point-design fighters with two pylon mounted missiles and aft tail controls (similar to several Soviet designs) have been investigated for a Mach number range from about 0.6 to 2.0. Whereas minimum drag penalties that are expected with the addition of external stores do occur, the effects at higher lifts, corresponding to maneuvering flight, are less severe and often favorable. The drag-due-to-lift factor is less with stores on although the lift curve slope is unaffected. The longitudinal stability level is reduced by the addition of stores while the pitch control effectiveness is unchanged. The directional stability was generally reduced at subsonic speeds and increased at supersonic speeds by the addition of stores but sufficiently high stability levels are obtainable that are compatible with the longitudinal maneuvering limits. Some examples of the potential maneuvering capability in terms of normal acceleration and turn radius are included.
    Keywords: AERODYNAMICS
    Type: Aircraft/Stores Compatibility Symposium; Oct 12, 1977 - Oct 14, 1977; Fort Walton Beach, FL
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    Forward flight effects on EBF noise (1977)
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    Publication Date: 2019-07-13
    Description: Forward flight effects on local mean velocity and turbulence velocity profiles, surface pressure spectra, and far field acoustic pressure spectra were measured for a simple externally blown flap (EBF). Both upper-surface-blowing and under-the-wing configurations were tested. Ratio of acoustic wind tunnel velocity to nozzle exhaust velocity was varied from 0 to 3/8 in steps of 1/8. A method was determined for predicting forward flight effects on surface-radiated noise. This noise is decreased in amplitude and shifted to higher frequency relative to data obtained at zero flight speed. Predictions are validated by comparisons with published NASA, Boeing, and Lockheed data.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-1314 , Aeroacoustics Conference; Oct 03, 1977 - Oct 05, 1977; Atlanta, GA
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    Computation of nonlinear one-dimensional waves in near-sonic flows (1977)
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    Publication Date: 2019-07-13
    Description: A nonlinear analysis is developed for sound propagation in a variable area duct in which the mean flow approaches choking conditions. A quasi-one-dimensional model is used; results of the standard linear theory are compared with the nonlinear results to assess the significance of the nonlinear terms. The nonlinear analysis represents the acoustic disturbance as a sum of interacting harmonics. Numerical results show that the basic signal is unaffected by the presence of higher harmonics if the throat Mach number is not too large, but as the Mach number approaches unity more harmonics are needed to describe the acoustic propagation. The strong interactions among harmonics in the numerical results occur in a region which is generally consistent with the nonlinear inner-expansion region of Callegari and Myers.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-1297 , Aeroacoustics Conference; Oct 03, 1977 - Oct 05, 1977; Atlanta, GA
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  • 37
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    Wing design by numerical optimization (1977)
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    Publication Date: 2019-07-13
    Description: A study was conducted to assess the feasibility of performing computerized wing design by numerical optimization. The design program combined a full potential, inviscid aerodynamics code with a conjugate gradient optimization algorithm. Three design problems were selected to demonstrate the design technique. The first involved modifying the upper surface of the inboard 50% of a swept wing to reduce the shock drag subject to a constraint on wing volume. The second involved modifying the entire upper surface of the same swept wing (except the tip section) to increase the lift-drag ratio subject to constraints on wing volume and lift coefficient. The final problem involved modifying the inboard 50% of a low-speed wing to achieve good stall progression. Results from the three cases indicate that the technique is sufficiently accurate to permit substantial improvement in the design objectives.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-1247 , Aircraft Systems and Technology Meeting; Aug 22, 1977 - Aug 24, 1977; Seattle, WA
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    Load distribution on a close-coupled wing canard at transonic speeds (1977)
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    Publication Date: 2019-07-13
    Description: This paper reports on a wind-tunnel test where load distributions were obtained at transonic speeds on both the canard and wing surfaces of a closely-coupled wing-canard configuration. The investigation included detailed component and configuration arrangement studies to provide insight into the various aerodynamic interference effects for the leading-edge vortex flow conditions encountered. Data indicate that increasing the Mach number from 0.70 to 0.95 caused the wing leading-edge vortex to burst over the wing when the wing was in the presence of the high canard. For some of the outboard span locations, the leading-edge vortex reattachment streamline intersects the wing trailing edge inboard of these span locations, thus, the Kutta condition was not satisfied. In general, the effect of adding a canard was to reduce the lift inboard and somewhat increase the lift outboard similar to the trends that would have been expected had the flow been attached.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-1132 , Atmospheric Flight Mechanics Conference; Aug 08, 1977 - Aug 10, 1977; Hollywood, FL
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    Maximum likelihood estimation of aerodynamic derivatives for an oblique wing aircraft from flight data (1977)
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    Publication Date: 2019-07-13
    Description: There are several practical problems in using current techniques on 5-degree-of-freedom equations to estimate the stability and control derivatives of oblique wing aircraft from flight data. A technique has been developed to estimate these derivatives by separating the analysis of the longitudinal and lateral-directional motion without neglecting cross-coupling effects. This technique was used on flight data from a remotely piloted oblique wing aircraft. The results demonstrated that the relatively simple approach developed was adequate to obtain high quality estimates of the aerodynamic derivatives of such aircraft.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-1135 , Atmospheric Flight Mechanics Conference; Aug 08, 1977 - Aug 10, 1977; Hollywood, FL
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    Simplified unsteady aerodynamic concepts, with application to parameter estimation (1977)
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    Publication Date: 2019-07-13
    Description: A simplified aerodynamic force model based on the physical principle of Prandtl's lifting line theory and trailing vortex concept has been developed to account for unsteadiness in the aircraft dynamics. The wake is assumed to be compressed to a single shed vortex element of appropriate strength moving downstream at a speed sufficient to approximate the Wagner function. Results are presented illustrating the ability of the simplified theory to duplicate exact solutions in unsteady aerodynamics. Further, consideration is given to the utility of the model in a parameter identification application.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-1124 , Atmospheric Flight Mechanics Conference; Aug 08, 1977 - Aug 10, 1977; Hollywood, FL
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    Active flutter control using generalized unsteady aerodynamic theory (1977)
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    Publication Date: 2019-07-13
    Description: This paper describes the application of generalized unsteady aerodynamic theory to the problem of active flutter control. The controllability of flutter modes is investigated. It is shown that the response of aeroelastic systems is composed of a portion due to a rational transform and a portion due to a nonrational transform. The oscillatory response characteristic of flutter is due to the rational portion, and a theorem is given concerning the construction of a linear, finite-dimensional model of this portion of the system. The resulting rational model is unique and does not require state augmentation. Active flutter control designs using optimal regulator synthesis are presented.
    Keywords: AERODYNAMICS
    Type: Guidance and Control Conference; Aug 08, 1977 - Aug 10, 1977; Hollywood, FL
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    Use of experimental separation limits in the theoretical design of V/STOL inlets (1977)
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    Publication Date: 2019-07-13
    Description: Experimental data from several model inlets have been used to generate two parameters which are related to the limit of operation for inlet flow separation. One parameter, called the diffusion ratio, is the ratio of the peak velocity on the inlet surface to the velocity at the diffuser exit and is related to the boundary-layer separation at low throat Mach numbers. The other parameter, the peak Mach number on the inlet surface, is related to the separation at high throat Mach numbers. These parameters are easily calculated from potential flow solutions and thus can be used as a design tool in screening proposed inlet geometries. Any of the geometric design variables can be analyzed by this technique; but, this paper is restricted to the consideration of the internal lip contraction ratio. An illustrative example of an application to an inlet design study for a tilt nacelle VTOL airplane is presented. The study will show what value of contraction ratio is required to meet the operating requirements yet allow the inlet to remain free of separation as indicated by the two separation parameters.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-878 , Propulsion Conference; Jul 11, 1977 - Jul 13, 1977; Orlando, FL; US
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    Upper surface blowing aerodynamic and acoustic characteristics (1977)
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    Publication Date: 2019-07-13
    Description: Aerodynamic performance at cruise, and noise effects due to variations in nacelle and wing geometry and mode of operation are studied using small aircraft models that simulate upper surface blowing (USB). At cruise speeds ranging from Mach .50 to Mach .82, the key determinants of drag/thrust penalties are found to be nozzle aspect ratio, boattailing angle, and chordwise position; number of nacelles; and streamlined versus symmetric configuration. Recommendations are made for obtaining favorable cruise configurations. The acoustic studies, which concentrate on the noise created by the jet exhaust flow and its interaction with wing and flap surfaces, isolate several important sources of USB noise, including nozzle shape, exit velocity, and impingement angle; flow pathlength; and flap angle and radius of curvature. Suggestions for lessening noise due to trailing edge flow velocity, flow pathlength, and flow spreading are given, though compromises between some design options may be necessary.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-608 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA; US
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    Theoretical study of hull-rotor aerodynamic interference on semibuoyant vehicles (1977)
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    Publication Date: 2019-07-13
    Description: Theoretical methods are being developed to predict the mutual interference between rotor wakes and the hull for semibuoyant vehicles. The objective of the investigation is to predict the pressure distribution and overall loads on the hull in the presence of rotors whose locations, tilt angles, and disk loading are arbitrarily specified. The methods involve development of potential flow models for the hull alone in a nonuniform onset flow, a rotor wake which has the proper features to predict induced flow outside the wake, and a wake centerline specification technique which accounts for the reactions of the wake to a nonuniform crossflow. The flow models are used in sequence to solve for the mutual influence of the hull and rotor(s) on each other and the resulting loads. A flow separation model is included to estimate the influence of separation on hull loads at high sideslip angles. Only limited results have been obtained to date. These were obtained on a configuration which was tested in the Ames Research Center 7- by 10-Foot Low Speed Tunnel under Goodyear Aircraft Corporation sponsorship and indicate the nature of the interference pressure distribution on a configuration in hover.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-1172 , Lighter Than Air Systems Technology Conference; Aug 11, 1977 - Aug 12, 1977; Melbourne, FL
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    Computation of viscous transonic flow about a lifting airfoil (1977)
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    Publication Date: 2019-07-13
    Description: The Reynolds averaged Navier-Stokes equations are solved numerically for the viscous transonic flow about a stationary NACA 64A010 airfoil in free air. This paper presents descriptions of the numerical method, turbulence models employed, and boundary conditions appropriate to simulation of free-air flight. Computed results are presented for the airfoil at a free-stream Mach number of 0.8, angles of attack of 0 and 2 deg, and a Reynolds number based on a chord of 4 x 10 to the 6th. For the lifting case, unsteady periodic motion was calculated along the aft portion of the airfoil and in its wake. Recent experimental results obtained by Johnson indicate periodicity aft of the shock closely approximates the computed frequency, but the amplitude of the disturbances was significantly less than the calculated amplitude.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-679 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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    Measurements of helicopter rotor tip vortices (1977)
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    Publication Date: 2019-07-13
    Description: This paper presents results from a recent wind-tunnel investigation of model helicopter rotor tip vortices. Measurements were made of the vortex positions, core sizes, and velocity distributions. A laser velocimeter was used to make the measurements, and a minicomputer-based data system was used to process the data and to aid in controlling the experiment. The velocimeter, the data system, and the software developed for the minicomputer are briefly described. The rotors investigated were two-bladed, teetering rotors with diameters of 2.1 m. Two sets of blades were used, one set with zero twist and one set with -11 deg of linear twist. The vortex positions were obtained by making flow field traverses while strobing the data system at a fixed azimuth. Aging of a vortex element was also studied by following the convected element while strobing the data system at different azimuths. By this method, the effects on the vortex of a close interaction with a blade and another vortex were studied.
    Keywords: AERODYNAMICS
    Type: AHS 77-33-06 , Annual National Forum; May 09, 1977 - May 11, 1977; Washington, DC
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    A study of the aerothermal environment for the Pioneer Venus multiprobe mission (1977)
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    Publication Date: 2019-07-13
    Description: In December 1978, four Pioneer Venus probe spacecraft are scheduled for almost simultaneous entry into the Venusian atmosphere at widely dispersed points about the planet. In this study, both detailed and approximate flow field analyses are used to define the entry aerothermal environment for the forebody of each of the four probes. The results show that approximate analyses can be used to predict inviscid radiative and laminar convective heating rates with acceptable accuracy. However, the radiative heating rates obtained with inviscid analyses are significantly greater than those obtained with a nonablating viscous-shock-layer (VSL) analysis, because the VSL analysis includes a strongly absorbing boundary layer. Also, the results show that the radiative heating is sensitive to small variations in atmospheric gas composition while the convective heating is not affected. With carbon-phenolic injection, the convective heating is reduced substantially while the overall radiative heating reduction is very small. Most of the radiative blockage occurs in the atomic line transitions which is significant only in the stagnation region.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-766 , Thermophysics Conference; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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    Evaluation of turbulence models for three primary types of shock-separated boundary layers (1977)
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    Publication Date: 2019-07-13
    Description: Zero-equation (algebraic), one-equation (kinetic energy), and two-equation (kinetic energy plus length scale) turbulence eddy viscosity models were used in computing three basic types of shock-separated boundary-layer flows. The three basic types of shock boundary-layer interaction discussed are: (1) a normal shock wave at transonic speeds, (2) a compression corner shock at supersonic speeds, and (3) an incident oblique shock at hypersonic speeds. The models tested are simple, unmodified models used extensively for incompressible, unseparated flows. A comparison of computed and measured results for the compressible, separated flows described herein indicates that model performance is dependent on flow configuration with no distinct superiority of one model over the other for all three flow configurations.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-692 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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    Calculation of transonic flow over supercritical airfoil sections (1977)
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    Publication Date: 2019-07-13
    Description: Two numerical methods for calculating the transonic flow, including viscous effects over lifting airfoil sections and experimental data are compared for turbulent flow over a supercritical airfoil. In addition, results for a NACA 64A010 airfoil at nonzero angle of attack are compared to demonstrate the applicability of the numerical methods to classical, lifting airfoils. One numerical method is a solution to the time-averaged Navier-Stokes equations throughout the entire flow field. The other is a hybrid method that combines inviscid, boundary-layer, and Navier-Stokes equations in appropriate regions of the flow field. Both methods adequately predict the surface pressures and flow field about the 64A010 airfoil at M = 0.8 and alpha = 2 deg when an appropriate turbulence model is used. The methods are not as successful for the supercritical airfoil.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-681 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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    Theory of viscous transonic flow over airfoils at high Reynolds number (1977)
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    Publication Date: 2019-07-13
    Description: This paper considers viscous flows with unseparated turbulent boundary layers over two-dimensional airfoils at transonic speeds. Conventional theoretical methods are based on boundary layer formulations which do not account for the effect of the curved wake and static pressure variations across the boundary layer in the trailing edge region. In this investigation an extended viscous theory is developed that accounts for both effects. The theory is based on a rational analysis of the strong turbulent interaction at airfoil trailing edges. The method of matched asymptotic expansions is employed to develop formal series solutions of the full Reynolds equations in the limit of Reynolds numbers tending to infinity. Procedures are developed for combining the local trailing edge solution with numerical methods for solving the full potential flow and boundary layer equations. Theoretical results indicate that conventional boundary layer methods account for only about 50% of the viscous effect on lift, the remaining contribution arising from wake curvature and normal pressure gradient effects.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-680 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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    Development of prediction techniques for multi-jet thermal ground flow fields and fountain formation (1977)
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    Publication Date: 2019-07-13
    Description: Avoiding detrimental ground interaction is important for practical V/STOL aircraft. This paper reports recent developments in a numerical method for estimating thermal ground footprints. Upwash and fountain formation for arbitrarily oriented jet arrangements is predicted. Flow asymmetry due to roll, pitch, differential thrust or ground inclination is included. The prediction methodology uses simple inviscid relations for energy and momentum conservation along with an empirical entrainment law, applied in independent sectors of the wall jet and upwash. Asymmetrical stagnation line prediction is compared with experiment. Detailed flow measurements for a three-jet interaction are also presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-616 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA; US
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    Vortices induced in a stagnation region by wakes - Their incipient formation and effects on heat transfer from cylinders (1977)
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    Publication Date: 2019-07-13
    Description: Horseshoe-like vortices, induced by wakes in the stagnation region of bluff bodies, are proposed as an efficient mechanism for augmentation of convective heat transfer. The vortex 'flow module' induced by single or multiple wakes, which had not been observed previously, was first documented and the resulting flow field was studied using various visualization techniques and hot-wire anemometry. In an attempt to understand the driving force behind this flow module, the conditions at which incipient formation of the vortices occurs were investigated. Existence of such a threshold is essential and was hitherto an open question in analytical studies of stability of flow in stagnation region. Finally, effects of the flow module on heat transfer from a cylinder were measured.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-790 , Thermophysics Conference; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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    Radiation induced precursor flow field ahead of a Jovian entry body (1977)
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    Publication Date: 2019-07-13
    Description: The change in flow properties ahead of the bow shock of a Jovian entry body, resulting from absorption of radiation from the shock layer, is investigated. Ultraviolet radiation is absorbed by the free stream gases, causing dissociation, ionization, and an increase in enthalpy of flow ahead of the shock wave. As a result of increased fluid enthalpy, the entire flow field in the precursor region is perturbed. The variation in flow properties is determined by employing the small perturbation technique of classical aerodynamics as well as the thin layer approximation for the preheating zone. By employing physically realistic models for radiative transfer, solutions are obtained for velocity, pressure, density, temperature, and enthalpy variations. The results indicate that the precursor effects, in general, are greater for lower altitudes and higher entry velocities. At higher altitudes precursor effects are felt farther in the free-stream. Just ahead of the shock the effects are larger at lower altitudes.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-768 , Thermophysics Conference; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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    Use of simplified flow separation criteria for slotted flap preliminary design (1977)
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    Publication Date: 2019-07-13
    Description: From experimental correlations of airfoil and flap pressure distributions, it is observed that flow separation is likely to occur when the canonical pressure recovery coefficient (C sub pr) exceeds a critical value. A procedure is described for obtaining the C sub pr parameter from modified inviscid analysis. The procedure has been applied to preliminary design studies of a new slotted flap to determine the influence of shape and location. Experiments are planned to evaluate the flap designed by this procedure.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 770481 , Business Aircraft Meeting; Mar 29, 1977 - Apr 01, 1977; Wichita, KS
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    In-flight measurements of the GA/W/-2 aerodynamic characteristics (1977)
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    Publication Date: 2019-07-13
    Description: Flight tests of a new 13% General Aviation Airfoil - the GA(W)-2 - gloved full span onto the existing wing of a Beech Sundowner have generated chordwise pressure distributions and wake surveys. Section lift, drag and moment coefficients derived from these measurements verify wind tunnel data and theory predicting the performance of this airfoil. The effect of steps, rivets and surface coatings upon the drag of the GA(W)-2 was also evaluated.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 770461 , Business Aircraft Meeting; Mar 29, 1977 - Apr 01, 1977; Wichita, KS
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    Studies of flow separation and stalling on one- and two-element airfoils at low speeds (1977)
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    Publication Date: 2019-07-13
    Description: Research has been conducted on the nature of airfoil behavior at pre- and post-separated angles of attack. Detailed wind tunnel studies have been made of boundary layer and wake fields for the GA(W)-1 airfoil, and the airfoil with a 0.3 chord Fowler flap. Experimental data are compared with theoretical predictions from a multi-element viscous flow computer program. Theoretical predictions are reasonably accurate for unseparated flows, but have serious errors when separation is present. Some recent techniques for modeling post-separated flow behavior are discussed in light of the present experiments.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 770442 , Business Aircraft Meeting; Mar 29, 1977 - Apr 01, 1977; Wichita, KS
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    Flight boundary layer transition measurements on a slender cone at Mach 20 (1977)
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    Publication Date: 2019-07-13
    Description: Experimental flight boundary layer transition data have been obtained on a 3.962-m-long, 5 deg half-angle cone with an initial nose radius of 0.254 cm. The data were obtained during re-entry from altitudes of approximately 30.480 to 18.288 km at a free-stream Mach number of 20. The free-stream Reynolds number varied from 6.56 x 10 to the 6th/m to 52.5 x 10 to the 6th/m, and the total enthalpy from about 18.3 to 16.9 MJ/kg. The locations of the beginning and end of transition were determined by the intersection of curves faired throug the laminar, transitional, and turbulent heating-rate data. The temperature-history technique for determining transition as currently used (sharp break in curve) was shown to compare unfavorably with the heating-rate-distribution method. The heating-rate-history technique, which is proportional to the temperature derivative and consequently more sensitive to perturbations, gives better agreement with the heating-rate distribution transition results.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-719 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 58
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    Application of numerical optimization to the design of supercritical airfoils without drag-creep (1977)
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    Publication Date: 2019-07-13
    Description: Recent applications of numerical optimization to the design of advanced airfoils for transonic aircraft have shown that low-drag sections can be developed for a given design Mach number without an accompanying drag increase at lower Mach numbers. This is achieved by imposing a constraint on the drag coefficient at an off-design Mach number while the drag at the design Mach number is the objective function. Such a procedure doubles the computation time over that for single design-point problems, but the final result is worth the increased cost of computation. The ability to treat such multiple design-point problems by numerical optimization has been enhanced by the development of improved airfoil shape functions. Such functions permit a considerable increase in the range of profiles attainable during the optimization process.
    Keywords: AERODYNAMICS
    Type: SAE PAPER 770440 , Business Aircraft Meeting; Mar 29, 1977 - Apr 01, 1977; Wichita, KS
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  • 59
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    The effect of blade sweep on propeller performance (1977)
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    Publication Date: 2019-07-13
    Description: The advanced propeller developed for high Mach number cruise incorporates swept blades to reduce compressibility losses. In order to evaluate the induced flow-field vortex lattice methods are applied to a swept propeller blade. The blade is modeled by a radial distribution of helical horseshoe vortices with a single swept bound vortex at the quarter chord and the control point at the three-quarter chord of each radial section. The results of numerical calculations show that the power coefficient decreases as the blade is swept and the power loading distribution shifts inboard.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-716 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 60
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    Flow study in the cross sectional planes of a turbine scroll (1977)
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    Publication Date: 2019-07-13
    Description: A numerical study of the nonviscous flow characteristics in the cross-sectional planes of a radial inflow turbine scroll is presented. The velocity potential is used in the formulation to determine the flow velocity in these planes resulting from the continuous mass discharge. The effect of the through flow velocity is simulated by a continuous distribution of source/sink in the cross-section. A special iterative procedure is devised to handle the solution of the resulting Poisson's differential equation with Neumann boundary conditions in a domain with generally curved boundaries. The analysis is used to determine the effects of the radius of curvature, the location of the scroll section and its geometry on the flow characteristics in the turbine scroll.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-714 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 61
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    Effect of surface cooling and roughness on transition for the Shuttle Orbiter (1977)
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    Publication Date: 2019-07-13
    Description: An analysis of roughness-induced boundary-layer transition examines the sensitivity of the Orbiter boundary-layer transition criteria to surface cooling, to surface roughness, and to the assumed flow-field model. The experimental data were obtained using a 0.0175-scale Orbiter with surface roughness represented by misaligned heat-shield tiles for surface temperatures from 0.12 stagnation temperature (a value typical of entry conditions) to 0.42 stagnation temperature (a value typical of continuous-flow wind-tunnels). Tile misalignment had only a slight effect on the heat transfer and on the trasition locations for wall temperature = 0.42 stagnation temperature. Cooling the boundary layer caused the tile-induced disturbances to increase significantly, promoting premature transition. Correlation of the effects of the misalignment height and of surface cooling in promoting transition are presented and predictions are made for typical Orbiter entry conditions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-704 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 62
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    Numerical solution of supersonic laminar flow over a three-dimensional compression corner (1977)
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    Publication Date: 2019-07-13
    Description: A newly developed, rapid numerical scheme is extended to three dimensions to solve the complete Navier-Stokes equations for a supersonic, laminar flow over a compression corner with sidewall effects. The program is coded so that it can solve for a general curved ramp surface geometry such as found in inlets and fuselage-wing-flap junctions. A test case of Mach 3.0 flow is calculated. In regions where three-dimensional effects are small, good agreement is obtained between the present calculation and previous two-dimensional solutions. In other regions, the results show complex three-dimensional flow-field interactions including shock-shock and shock/boundary-layer interactions
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-694 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 63
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    Direct measurements of wall shear stress by buried wire gages in a shock-wave boundary-layer interaction region (1977)
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    Publication Date: 2019-07-13
    Description: Detailed measurements of wall shear stress (skin friction) were made with specially developed buried wire gages in the interaction regions of a Mach 2.9 turbulent boundary layer with externally generated shocks. Separation and reattachment points inferred by these measurements support the findings of earlier experiments which used a surface oil flow technique and pitot profile measurements. The measurements further indicate that the boundary layer tends to attain significantly higher skin-friction values downstream of the interaction region as compared to upstream. Comparisons between measured wall shear stress and published results of some theoretical calculation schemes show that the general, but not detailed, behavior is predicted well by such schemes.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-691 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 64
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    Form drag, skin friction, and vortex shedding frequencies for subsonic and transonic crossflows on circular cylinder (1977)
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    Publication Date: 2019-07-13
    Description: A series of wind-tunnel tests covering a range of Mach numbers and Reynolds numbers in subsonic and transonic flows was conducted on a circular cylinder placed normal to the flow. Form drag coefficients were determined from surface-pressure measurements and displayed as a function of Mach number to show the drag rise phenomenon. Buried wire gages arranged on the model surface were used to measure skin-friction distributions and vortex-shedding frequencies at different flow conditions. It was found that detectable periodic shedding ceases above M = 0.9. The measured skin-friction distributions indicate the positions of mean separation points clearly; these values are documented for the different flow conditions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-687 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 65
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    An experimental and computational investigation of the steady and unsteady transonic flow fields about an airfoil in a solid-wall test channel (1977)
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    Publication Date: 2019-07-13
    Description: An experimental and computational investigation of the steady and unsteady transonic flow field about a thick airfoil is described. An operational computer code for solving the two-dimensional, compressible Navier-Stokes equations for flow over airfoils was modified to include solid-wall, slipflow boundary conditions to properly assess the code and help guide the development of improved turbulence models. Steady and unsteady flow fields about an 18% thick circular arc airfoil at Mach numbers of 0.720, 0.754, and 0.783 and a chord Reynolds number of 11 x 10 to the 6th are predicted and compared with experiment. For the first time, computed results for unsteady turbulent flows with separation caused by a shock wave were obtained which qualitatively reproduce the time-dependent aspects of experiments. Features such as the intensity and reduced frequency of airfoil surface-pressure fluctuations, oscillatory regions of trailing-edge and shock-induced separation, and the Mach number range for unsteady flows were all qualitatively reproduced.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-678 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 66
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    Lift enhancement by an externally trapped vortex (1977)
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    Publication Date: 2019-07-13
    Description: A theoretical study is made of the performance capabilities of a lift concept that utilizes a spanwise vortex over the upper surface of the wing. The vortex is generated by a vertical flap near the leading edge of the wing and maintained by suction through orifices in endplates at the wingtip. The analysis approximates the three-dimensional flow field with a two-dimensional configuration that is mapped by conformal transformation into the flow about a circle. Theoretical solutions for a range of flap and orifice configurations predict that section lift coefficients up to around 10 can be achieved. It is concluded that such a lift concept is applicable to STOL aircraft if the vortex can be adequately stabilized and if the endplate suction can be generated efficiently.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-672 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 67
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    Effect of wing fins on lift-generated wakes (1977)
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    Publication Date: 2019-07-13
    Description: A theoretical and experimental study has been made of the effect of wing-mounted fins on the vortex wakes of subsonic aircraft. The theory is used (a) to gain an understanding of wake alleviation by vortex injection and (b) to guide the experimental investigation. Wind-tunnel tests were used to evaluate the alleviation achievable and to find the optimum values for the various fin parameters. It was found that vertical fins mounted on the upper surface of a wing could lower the wake-induced rolling moments on an encountering wing by a factor of 3 or more. The most promising fin configuration found for the Boeing 747 model is a fin positioned 48% outboard from the centerline to the wingtip with a height of 0.014 span, a chord of 0.085 span, and an 18 deg angle of attack. This fin configuration caused a 10% increase in drag but no lift penalty.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-671 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 68
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    Rolling moments in a trailing vortex flow field (1977)
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    Publication Date: 2019-07-13
    Description: Pressure distributions are presented which were measured on a wing in close proximity to a tip vortex of known structure generated by a larger, upstream semispan wing. Overall loads calculated by integration of these pressures are checked by independent measurements made with an identical model mounted on a force balance. Several conventional methods of wing analysis are used to predict the loads on the following wing. Strip theory is shown to give uniformly poor results for loading distribution, although predictions of overall lift and rolling moment are sometimes acceptable. Good results are obtained for overall coefficients and loading distribution by using linearized pressures in vortex-lattice theory in conjunction with a rectilinear vortex. The equivalent relation from reverse-flow theory that can be used to give economic predictions for overall loads is presented.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-670 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 69
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    Effect of angle of attack and Mach number on slender wing aerodynamics (1977)
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    Publication Date: 2019-07-13
    Description: An analytic theory is presented in which the classical slender wing theory is modified to account for the combined effects of large angle of attack and nonsonic Mach number on the unsteady aerodynamics. The computed results agree well with available static and dynamic experimental data for slender delta wings in the freestream Mach number range between 0 and 2.8. The method was extended to compute the unsteady aerodynamics of the space shuttle orbiter by defining an equivalent slender wing using static experimental data. The results obtained in this manner are in good agreement with dynamic experimental results for the freestream Mach number range between 0.3 and 1.2.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-667 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 70
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    Aerodynamics of slender finned bodies at large angles of attack (1977)
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    Publication Date: 2019-07-13
    Description: In certain missions finned missiles perform slewing maneuvers. Here, large angles of attack are attained. Experimental data needed to understand the aerodynamics of such vehicles are presented. The purpose of this investigation was to study the interaction of the body flow field with that produced by the fins and the resulting effects on the aerodynamic forces and moments. The experiments were conducted at a nominal Mach number of 2.7 and angles of attack from 0 to 50 deg, with two different models. The tests were performed in a range of Reynolds number from 1.5 x 10 to the 6th to 4 x 10 to the 7th per foot (to cover both the laminar and fully turbulent regimes.) Several fin roll angles were investigated. Static pressures on both body and fin surfaces are reported.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-666 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 71
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    Implicit finite difference simulation of flow about arbitrary geometries with application to airfoils (1977)
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    Publication Date: 2019-07-13
    Description: Finite difference procedures are used to solve either the Euler equations or the 'thin layer' Navier-Stokes equations subject to arbitrary boundary conditions. An automatic grid generation program is employed, and because an implicit finite difference algorithm for the flow equations is used, time steps are not severely limited when grid points are finely distributed. Computational efficiency and compatibility to vectorized computer processors is maintained by use of approximate factorization techniques. Computed results for both inviscid and viscous flow about airfoils are described and compared to various known solutions.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-665 , Conference on Fluid and Plasmadynamics; Jun 27, 1977 - Jun 29, 1977; Albuquerque, NM
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  • 72
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    A finite volume method for transonic potential flow calculations (1977)
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    Publication Date: 2019-07-13
    Description: It is proposed to solve the exact transonic potential flow equation on a mesh constructed from small volume elements, which can be conveniently packed around any reasonably smooth configuration. The calculation is performed on two sets of interlocking cells. The velocity and density are calculated in the primary cells, and a flux balance is then established in the secondary cells. The scheme is desymmetrized by the addition of artificial viscosity in the supersonic zone. Some results are included for a swept wing and a wing-cylinder combination.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-635 , Computational Fluid Dynamics Conference; Jun 27, 1977 - Jun 28, 1977; Albuquerque, NM
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  • 73
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    An implicit shock-fitting scheme for unsteady transonic flow computations (1977)
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    Publication Date: 2019-07-13
    Description: The alternating-direction implicit scheme developed by NASA Ames for unsteady transonic flows has been modified to include a shock-fitting algorithm as well as an analytically stretched coordinate system. The shock-fitting procedure treats shock waves as discontinuities normal to the free stream. Improvements in shock position and the unsteady pressure distributions are obtained by this modification. The various types of shock motion observed experimentally by Tijdeman are well simulated in calculations using the modified computational scheme. The method of detecting shock wave formation and the procedure for fitting a moving shock wave are illustrated. Results for a pulsating parabolic arc airfoil and for an NACA 64A006 airfoil with oscillating quarter-chord flap are presented and discussed.
    Keywords: AERODYNAMICS
    Type: AD-A067480 , AFOSR-TR-79-0380 , AIAA PAPER 77-633 , Computational Fluid Dynamics Conference; Jun 27, 1977 - Jun 28, 1977; Albuquerque, NM
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  • 74
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    The transonic multi-foil Augmentor-Wing (1977)
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    Description: The paper describes the development of a transonic blown multi-foil Augmentor-Wing airfoil section that has a thickness/chord (t/c) value of 0.18. In comparison with an unblown single-foil supercritical section of the same overall t/c the new multi-foil section is characterized by an increased drag rise Mach number, increased buffet boundaries, and a reduction in 'effective' drag due to blowing. Potential advantages of the Augmentor-Wing are considered and the testing of three high-speed models in a trisonic pressurized wind tunnel (possessing a two-dimensional transonic insert) is discussed. The data indicate that a very thick wing is feasible since separations toward the rear of the main foil can be controlled both by shroud location and augmentor blowing.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-606 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA; US
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  • 75
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    A lifting surface theory for thrust augmenting ejectors (1977)
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    Publication Date: 2019-07-13
    Description: The circulation theory of airfoil lift has been applied to calculate the performance of thrust augmenting ejectors. The ejector shroud is considered to be 'flying' in the secondary velocity field induced by the entrainment of the primary jet, so that the augmenting thrust is viewed as analogous to the lift on an airfoil. Vortex lattice methods are utilized to compute the thrust augmentation from the force on the flaps. The augmentation is shown to be a function of the length and shape of the flaps, as well as their position and orientation. Predictions of this new theory are compared with the results of classical methods of calculating the augmentation by integration of the stream thrust.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-604 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA; US
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    Surface fluctuating pressure measurements on a 1/4-scale YC-14 boilerplate model (1977)
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    Description: A research program is conducted for the study of the fluctuating loads imposed on both upper-surface blown-flap and externally blown-flap powered-lift STOL aircraft configurations by the impingement of the jet engine exhaust flow. Attention is given to the measurement of the unsteady pressures at 30 positions in the vicinity of the jet exhaust on the surface of a NASA 1/4-scale YC-14 boilerplate wing and fuselage section.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-592 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA
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  • 77
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    Effects of jet decay rate on jet induced loads on a flat plate (1977)
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    Publication Date: 2019-07-13
    Description: Experimental modelling of the interaction between a jet and an aircraft wing or fuselage in VTOL aircraft was undertaken using a cold jet exiting perpendicular to a flat plate in a uniform cross-flow. Effects of jet decay rate and jet-to-cross-flow velocity ratio, R, on the induced load distribution were investigated. Jet decay rate was increased by using cylindrical centerbodies submerged in the jet nozzle, which caused nonuniform initial jet velocity profiles. Quicker jet decay rate, corresponding to the presence of a centerbody, resulted in as much as 50% reduction in the induced pressure loads on the plate. This has implications in interpretation of results from earlier VTOL model studies of jet induced loads, where the jets have often had relatively slow decay rates due to uniform initial velocity profiles
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-596 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA
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    Modelling techniques for jet impingement (1977)
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    Description: A technique for testing scale models for the determination of fluctuating pressure loads due to jet impingement has been investigated using a quarter-scale model of a boilerplate test facility in which a JT-15D engine with a rectangular outer nozzle blows over a small curved airfoil representing the upper-surface of a wing. When model and full-scale spectra of fluctuating surface pressures are reduced to plots of pressure coefficient power-spectral density vs Strouhal number, moderate agreement is obtained, but a shift of spectral peaks is noted. However, when a correction for the ratio of average jet to ambient temperature is applied, the spectral peaks agree.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-591 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA
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  • 79
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    Fluctuating loads on the flap surfaces of an externally-blown-flap configuration (1977)
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    Publication Date: 2019-07-13
    Description: An experimental program to obtain the fluctuating loads on the surfaces of a triple-slotted externally-blown-flap powered-lift STOL configuration was conducted. A large model of a wing/flap system and a TF-34 medium bypass ratio engine was investigated. Measurements of the fluctuating pressure, static pressure, and surface temperature resulting from the jet impingement were obtained at several locations on the surfaces of the second and third flaps. Fluctuating pressure data include overall level, power-spectral density (PSD), cross-correlation coefficient, coherency, and phase angle of the cross power-spectral density. These data indicate that more than one mechanism contributes to the fluctuating pressure levels on the flaps. In the immediate area above the intersection of the engine centerline and the flap, low frequency pressures dominate the overall fluctuating pressure levels. In other areas, such as below this intersection and outboard on the flaps, the PSD curve reaches a peak value at a Strouhal number ranging from 0.22 to 0.45.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-589 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA
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  • 80
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    Theoretical prediction of over-wing-blowing aerodynamics (1977)
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    Publication Date: 2019-07-13
    Description: A theoretical method is developed for predicting the aerodynamic characteristics of wings with over-wing-blowing jet. The method allows the jet to stay above the wing surface as well as to wash the surface. It accounts for the wing-jet interaction due to differences between the jet and freestream dynamic pressures and Mach numbers, in addition to the jet entrainment. For the former effect, the quasi-vortex-lattice method is used to satisfy the jet and wing boundary conditions. For the latter, a new theory was developed to calculate the jet entrained flow for given jet properties. Comparison of predicted results with available data of various configurations shows reasonably good agreement. Further theoretical analysis indicates that it is aerodynamically advantageous to locate the jet exit near and ahead of the wing leading edge, and that the camber shape has significant effect on the induced drag.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-575 , V/STOL Conference; Jun 06, 1977 - Jun 08, 1977; Palo Alto, CA
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  • 81
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    Vortex pairing and organized structures in axisymmetric jets under controlled excitation (1977)
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    Description: A description is given of experiments which have been carried out in a circular air jet facility consisting of two settling chambers in sequence. Sinusoidal perturbations in the exit profile are introduced at controlled frequencies and amplitudes with the aid of a loudspeaker attached to the wall of the first chamber. It was found that vortex pairing in circular jets can occur in two distinct modes, including the shear layer mode and the jet mode. Amplitude variations, the conditions for strong vortex pairing, and the spectral evolution downstream are illustrated with the aid of graphs.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Apr 18, 1977 - Apr 20, 1977; University Park, PA
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  • 82
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    Boundary layer shear stress in subsonic and supersonic flow (1977)
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    Description: A wide range of shear stress distributions for turbulent boundary layers is examined. A solution for the shear stress in terms of the mean flow is obtained for the limiting case of large Reynolds numbers. Attention is given to turbulent boundary layer shear stress, zero pressure gradient flow, increasing pressure gradient flow, and decreasing pressure gradient flow.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Apr 18, 1977 - Apr 20, 1977; University Park, PA
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    A critical evaluation of invariant second-order closure models for subsonic boundary layers (1977)
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    Publication Date: 2019-07-13
    Description: Computations based on several second-order turbulence models, including full Reynolds stress and two-equation models, are compared with a number of boundary-layer experiments. In general, the models represent the data reasonably well, with skin friction tending to be somewhat overpredicted in the far downstream region of the adverse pressure gradient experiments. A discussion of the behavior of the ARAP full Reynolds stress model in predicting the components of the Reynolds stress tensor is given. It is concluded that compatibility at the wall may necessitate the use of more than one length scale.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Apr 18, 1977 - Apr 20, 1977; University Park, PA
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  • 84
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    Numerical solution of three-dimensional free turbulent shear flows (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Numerical results are presented for three-dimensional compressible turbulent jet and wake flows. An alternating direction implicit numerical procedure is used to solve the finite-difference form of the parabolic elliptic Navier-Stokes equations. A coordinate transformation maps the boundaries at infinity into a finite computational domain in order to properly specify infinity boundary conditions as well as contain the downstream growth of the viscous flow field in a fixed computational grid. Turbulence closure is achieved through an algebraic mixing length eddy viscosity model. Numerical results for supersonic flow are presented for an axisymmetric jet, an elliptical jet, an elliptical wake, and two interacting rectangular jets. Experimental data were not available for comparison with the numerical results. However, the results compare well with empirical results for free shear flows.
    Keywords: AERODYNAMICS
    Type: Symposium on Turbulent Shear Flows; Apr 18, 1977 - Apr 20, 1977; University Park, PA
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  • 85
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    A simplified theory of oscillating airfoils in transonic flow - Review and extension (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Significant old and new results are presented to show to what extent a simplified theory for transonic flow may be used. Solutions are obtained by classical techniques and compared with experiment. Results are given for two-dimensional, steady and unsteady flow and three-dimensional, steady flow. The effects of flow separation and improvements in Bernoulli's equations and the surface boundary condition are also briefly discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-445 , Conference on Structures, Structural Dynamics and Materials; Mar 21, 1977 - Mar 23, 1977; San Diego, CA; US|Mar 24, 1977 - Mar 25, 1977
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  • 86
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    Nonlinear, unsteady aerodynamic loads on rectangular and delta wings (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Nonlinear unsteady aerodynamic loads on rectangular and delta wings in an incompressible flow are calculated by using an unsteady vortex-lattice model. Examples include flows past fixed wings in unsteady uniform streams and flows past wings undergoing unsteady motions. The unsteadiness may be due to gusty winds or pitching oscillations. The present technique establishes a reliable approach which can be utilized in the analysis of problems associated with the dynamics and aeroelasticity of wings within a wide range of angles of attack.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-156 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 87
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    Experiments on transonic and supersonic turbulent boundary-layer separation (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Results of experimental investigations into turbulent boundary-layer behavior under the influence of pressure gradients and with separation are presented for transonic and supersonic flow fields. In the transonic case, an axisymmetric model was implemented consisting of an annular circular arc bump affixed to a circular cylinder aligned with the flow direction. For the supersonic separation study, an oblique shock wave impinging on the wind tunnel wall boundary layer was employed to cause separation. The mean streamwise and normal velocity components as well as the respective turbulence intensities were obtained with a two-color frequency shifted laser velocimeter.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-47 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 88
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    Investigations related to the inviscid-viscous interaction in transonic flows about finite 3-D wings (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Inviscid small-disturbance theory has been shown to predict three-dimensional transonic flows about finite wings reasonably well as long as viscous effects are negligible. In order to include these effects, the inviscid small-disturbance solution of Bailey and Ballhaus (1975) has been combined with a finite-difference solution for Prandtl's boundary-layer equations. This solution employs the conditionally stable Krause (1968) scheme, implicit in the direction normal to the wall, to cope with the domain-of-dependence problem that arises for reverse cross flow. To be consistent with the inviscid-flow solution, the boundary layer is computed in the representative wing planform plane which is transformed into rectangular shape in the computational domain. The flow has been assumed turbulent, and a scalar eddy-viscosity model is adopted. The interaction between inviscid and viscous flow is modeled with the help of the displacement surface which is added to the geometric wing shape. Sample distributions of displacement thickness for swept wings are presented for weak and strong interaction cases.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-209 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 89
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    Supersonic flow about circular cones at large angles of attack - A floating discontinuity approach (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The technique of floating shock fitting is adapted to the computation of the inviscid flowfield about circular cones in a supersonic free stream at angles of attack that exceed the cone half-angle. In those regions in which the governing conical equations are mixed elliptic-hyperbolic, the fully hyperbolic form is obtained by the addition of the temporal derivative. The resulting equations are applicable over the complete range of free-stream Mach numbers, angles of attack and cone half-angles for which the bow shock is attached. An explicit finite-difference algorithm is used to obtain the solution by an unsteady relaxation approach. The bow shock, embedded crossflow shock, and vortical singularity in the leeward symmetry plane are all treated as floating discontinuities in a fixed computational mesh. The method yields excellent results for the bow and embedded shocks, however, the solution in the leeward symmetry plane exhibits viscous-like effects and does not appear to adequately predict the behavior of the vortical singularity.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-86 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 90
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    Prediction of laminar and turbulent boundary layer flow separation in V/STOL engine inlets (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The paper provides a theoretical description of the development of the boundary layer on the lip and diffuser surface of a subsonic inlet at arbitrary operating conditions of mass flow rate, freestream velocity and incidence angle. Both laminar separation on the lip and turbulent separation in the diffuser are discussed. The agreement of the theoretical results with model experimental data illustrates the capability of the theory to predict separation. The effects of throat Mach number, inlet size, and surface roughness on boundary-layer development and separation are illustrated.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-144 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 91
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    Perturbation of a discontinuous transonic flow (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The main difficulty in perturbing a discontinuous transonic flow is in the representation of the shift in the location of the discontinuity (shock wave). Herein presented is a method of overcoming this difficulty by using a distorted airfoil as the initial case rather than the real physical airfoil; the distortion is chosen such that the shock location is unchanged by the perturbation. The distorted airfoil is obtained by the use of a strained coordinate system. A direct consequence of the theory is the derivation of an algebraic similarity relation between related airfoils with shock waves at differing locations. Results for simple examples are shown.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-206 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 92
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    Analytical study of viscous effects on transonic flow over boattail nozzles (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An analytical study has been made of the effects of viscous/inviscid interactions on the transonic flow over boattail nozzles. The theoretical method couples a relaxation solution of the full potential transonic flow equations with a conventional boundary-layer solution to account for displacement-thickness effects. Surface pressures calculated on circular-arc boattails with solid jet-plume simulators show good agreement with experiment for free-stream Mach numbers less than 0.90. For separated flows, an empirical discriminating streamline model of the separation bubble gives good results until the onset of shock-induced separation, which occurs typically at a Mach number of about 0.90.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-223 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 93
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    Transonic performance of an auxiliary airflow system for axisymmetric inlets (1977)
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    Publication Date: 2019-07-13
    Description: A large-scale model of an axisymmetric inlet with a centerbody auxiliary airflow system has been tested in the wind tunnel at transonic speeds. The auxiliary system allows additional airflow (other than in the main duct formed by the cowl and translating centerbody) to pass through the centerbody of the inlet and combine with the main duct airflow on its way to the engine face. The results of the tests are presented, and the inlet performance is compared to a closely related alternative inlet with a 'traveling' boundary-layer bleed system which precludes the use of a centerbody auxiliary airflow system. The comparison shows that the auxiliary airflow inlet can supply 7.7% more engine face airflow at Mach number 1.0 and is 26% shorter than the traveling bleed inlet. Even though maximum transonic airflow was not achieved at a comparable engine face mass-flow ratio of 0.580, a total-pressure distortion of 0.10 and a total-pressure recovery of 0.985 were achieved for the auxiliary airflow inlet while a recovery of only 0.965 was achieved for the traveling bleed inlet.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-148 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 94
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    A critique of some recent second-order turbulence closure models for compressible boundary layers (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Computations based on two recently developed second-order turbulence closure models are compared with a series of boundary-layer experiments and with predictions of these experiments using an algebraic mixing length model. One of the models employs an eddy viscosity, whereas the other evaluates components of the Reynolds stress tensor. For flat plates, the computations are compared with the van Driest skin-friction transformation to assess the handling of compressibility. For boundary layers in pressure gradients, four experiments at Mach 4 and one at Mach 6.7 are used as the bases for comparison. In general, both models represent mean velocities and skin friction reasonably well, but represent the turbulence shear stress less accurately.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-128 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 95
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    Turbulence measurements in axisymmetric supersonic boundary layer flow in adverse pressure gradients (1977)
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    Publication Date: 2019-07-13
    Description: Mean flow and turbulence measurements are presented for adiabatic compressible turbulent boundary layer flow in adverse pressure gradients. The gradients were induced on the wall of an axially symmetric wind tunnel by contoured centerbodies mounted on the wind tunnel centerline. The boundary layer turbulence downstream of a boundary layer bleed section in a zero pressure gradient was also examined. The measurements were obtained using a constant temperature hot-wire anemometer. The adverse pressure gradients were found to significantly alter the turbulence properties of the boundary layer. With flow through the bleed holes there was a measureable decrease in the rms longitudinal velocity fluctuations near the wall and the turbulent shear stress in the boundary layer was reduced.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-129 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 96
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    Acoustic signatures of a model fan in the NASA-Lewis anechoic wind tunnel (1977)
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    Publication Date: 2019-07-13
    Description: One-third octave band and narrowband spectra and continuous directivity patterns radiated from an inlet are presented over ranges of fan operating conditions, tunnel velocity, and angle of attack. Tunnel flow markedly reduced the unsteadiness and level of the blade passage tone, revealed the cut-off design feature of the blade passage tone, and exposed a lobular directivity pattern for the second harmonic tone. The full effects of tunnel flow are shown to be complete above a tunnel velocity of 20 meters/second. The acoustic signatures are also shown to be strongly affected by fan rotational speed, fan blade loading, and inlet angle of attack.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-59 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 97
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    A numerical method for the exact calculation of airloads associated with impulsively started wings (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A numerical method is developed to calculate three-dimensional potential flows due to the steady and impulsive motion of isolated wing and wing-wing interaction problems. The velocity potential is represented by a discrete set of constant-doublet quadrilaterals on wing and wake surfaces. The exact surface boundary condition is enforced, and the solution is obtained in a step-by-step fashion, configurations being impulsively started from rest. Free-wake geometries are generated for each time step with Rankine or Lamb viscous vortex segments used in wake-velocity calculations. Sample results include calculated performance to steady state for a thick wing and indicial lift of a wing-wing interaction problem.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 77-2 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 98
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    A general method for calculating three-dimensional compressible laminar and turbulent boundary layers on arbitrary wings (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The method described utilizes a nonorthogonal coordinate system for boundary-layer calculations. It includes a geometry program that represents the wing analytically, and a velocity program that computes the external velocity components from a given experimental pressure distribution when the external velocity distribution is not computed theoretically. The boundary layer method is general, however, and can also be used for an external velocity distribution computed theoretically. Several test cases were computed by this method and the results were checked with other numerical calculations and with experiments when available. A typical computation time (CPU) on an IBM 370/165 computer for one surface of a wing which roughly consist of 30 spanwise stations and 25 streamwise stations, with 30 points across the boundary layer is less than 30 seconds for an incompressible flow and a little more for a compressible flow.
    Keywords: AERODYNAMICS
    Type: NASA-CR-2777
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  • 99
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    Review of experimental work on transonic flow in turbomachinery (1977)
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    Publication Date: 2019-07-13
    Description: The review is primarily concerned with modern experimental techniques of high response and laser supported instrumentation. The considered techniques make it possible to obtain detailed data of steady and unsteady processes occurring inside transonic blade rows and in the vicinity of the rows. Such data are needed for the verification of computer codes used for the study of the operational characteristics of turbomachinery. Attention is given to high response transducers, hot wire probes, hot film gages, laser Doppler velocimeter systems, laser fluorescence, and laser holography.
    Keywords: AERODYNAMICS
    Type: Transonic flow problems in turbomachinery; Feb 11, 1976 - Feb 12, 1976; Monterey, CA
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  • 100
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    Normal shock wave-turbulent boundary layer interactions in transonic flow near separation (1977)
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    Publication Date: 2019-07-13
    Description: The problem of a normal shock wave impinging on a flat plate, turbulent boundary layer is considered for the case where the external flow is transonic. Asymptotic methods are employed. It is shown that there are two outer regions, including the outer part of the boundary layer and the external flow, in which inviscid flow governing equations hold, and two regions near the wall, in which Reynolds and/or viscous stresses need be taken into account. The solutions in the outer regions lead to the pressure distribution on the wall, for which an analytical expression is presented, valid under those conditions when separation is imminent but has not yet occurred. The solutions valid in the inner regions lead to a separation criterion.
    Keywords: AERODYNAMICS
    Type: Transonic flow problems in turbomachinery; Feb 11, 1976 - Feb 12, 1976; Monterey, CA
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