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  • AERODYNAMICS  (860)
  • 1995-1999
  • 1980-1984  (479)
  • 1975-1979  (381)
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  • 1983  (479)
  • 1978  (381)
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  • 1995-1999
  • 1980-1984  (479)
  • 1975-1979  (381)
Year
  • 1
    Publication Date: 2006-02-22
    Description: An experimental study of slotted upper and lower walls in a two dimensional transonic wind tunnel with solid sidewalls is reported. Results are presented for several slot spacings and slot openness ratios. The experimental data were pressure measurements which were made on an airfoil model and on a sidewall near one of the slotted walls. The slotted-wall boundary condition coefficient, which related the pressure and streamline curvature near the wall, was determined from the wall pressure measurements. The measured wall-induced interference was correlated with the experimental values for the boundary condition coefficient. This correlation was compared with theory.
    Keywords: AERODYNAMICS
    Type: Advanced Technol. Airfoil Res., Vol. 1, Pt. 2; p 459-471
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  • 2
    Publication Date: 2006-02-22
    Description: Finite difference procedures were successfully used to solve the steady transonic flow about airfoils and appear to provide a practical means for calculating the corresponding unsteady flow. The purpose of the paper is to describe a finite difference procedure derived from the equations for the potential flow by assuming small perturbations and harmonic motion. The velocity potential is divided into steady and unsteady parts, and the resulting unsteady equation is linearized on the basis of small amplitudes of oscillation. The steady velocity potential, which must be calculated first, is described by the classical nonlinear transonic differential equation.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Advanced Technol. Airfoil Res., Vol. 1, Pt. 2; p 657-670
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  • 3
    Publication Date: 2006-02-22
    Description: An in-flight wing wake section drag investigation was conducted using traversing pitot and static probes. The primary objective was to develop measurement techniques and improve the accuracy of in-flight wing profile drag measurements for low values of dynamic pressure and Reynolds number. Data were obtained on a sailplane for speeds from about 40 knots to 125 knots at chord Reynolds numbers between 1,000,000 and 3,000,000. Tests were conducted with zero flap deflection, deflected flaps, and various degrees of surface roughness, and for smooth and rough atmospheric conditions. Several techniques were used to increase data reliability and to minimize certain bias errors. A discussion of the effects of a total pressure probe in a pressure gradient, and the effects of discrete turbulence levels, on the data presented and other experimental results is also included.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Advanced Technol. Airfoil Res., Vol. 1, Pt. 2; p 601-621
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  • 4
    Publication Date: 2006-02-22
    Description: A method for calculating the transonic flow over steady and oscillating airfoils was developed by Isogai. It solves the full potential equation with a semi-implicit, time-marching, finite difference technique. Steady flow solutions are obtained from time asymptotic solutions for a steady airfoil. Corresponding oscillatory solutions are obtained by initiating an oscillation and marching in time for several cycles until a converged periodic solution is achieved. In this paper the method is described in general terms, and results are compared with experimental data for both steady flow and for oscillations at several values of reduced frequency. Good agreement for static pressures is shown for subcritical speeds, with increasing deviation as Mach number is increased into the supercritical speed range. Fair agreement with experiment was obtained at high reduced frequencies with larger deviations at low reduced frequencies.
    Keywords: AERODYNAMICS
    Type: Advanced Technol. Airfoil Res., Vol. 1, Pt. 2; p 689-700
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  • 5
    Publication Date: 2006-02-22
    Description: The uses of laser Doppler velocimeter, hot wire, and surface hot film techniques in the study of turbulent flows are described, and data obtained in compressible flows are discussed. Applications are illustrated with measurements of wind tunnel freestream turbulence characteristics and with data obtained in transitional, turbulent, and separated shear flows. A new method which was developed for the study of time dependent and unsteady turbulent flows is also presented.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Advanced Technol. Airfoil Res., Vol. 1, Pt. 2; p 571-588
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  • 6
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 607-63
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  • 7
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 557-58
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  • 8
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 539-55
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  • 9
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 461-49
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  • 10
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    Publication Date: 2011-08-18
    Description: The potential of planform modification and hinge-line relocation to improve the thrust efficiency of vortex flaps was experimentally investigated on a 60-deg cropped delta wing model. Spanwise segmentation of the flap, together with chord-tailoring of the segments, allowed the vortex to be maintained on the outboard flap surfaces to higher angles of attack. In addition, location of the flap hinge aft of and underneath the wing leading edge generated substantial thrust from the vortex suction acting on the leading-edge lower surface. A combination of these beneficial effects allowed the flap/wing area to be reduced from 11.4 percent of the continuous flap to 6.3 percent of segmented flap, essentially without detriment to the incremental lift-to-drag ratio due to flap addition in the lift coefficient range 0.5-0.7 based on the basic wing area.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 20; 1062-106
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  • 11
    Publication Date: 2011-08-18
    Description: Previously cited in issue 20, p. 3138, Accession no. A82-40893
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 20; 993-1006
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  • 12
    Publication Date: 2011-08-18
    Description: Previously cited in issue 06, p. 799, Accession no. A82-17876
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 21; 1611-161
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  • 13
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    Publication Date: 2011-08-18
    Description: A mesh system composed of multiple overset body-conforming grids is described for adapting finite-difference procedures to complex aircraft configurations. In this so-called 'chimera mesh,' a major grid is generated about a main component of the configuration and overset minor grids are used to resolve all other features. Methods for connecting overset multiple grids and modifications of flow-simulation algorithms are discussed. Computational tests in two dimensions indicate that the use of multiple overset grids can simplify the task of grid generation without an adverse effect on flow-field algorithms and computer code complexity.
    Keywords: AERODYNAMICS
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  • 14
    Publication Date: 2011-08-18
    Description: Previously cited in issue 17, p. 2873, Accession no. A81-38082
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 21; 1492-149
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  • 15
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    Publication Date: 2011-08-18
    Description: The tethered satellite concept provides an ideal platform for the study of the interaction of the atmosphere with satellites of various shapes and surfaces under a wide range of flow conditions. From experiments which would measure the drag, lift, and torque acting on the tethered satellite, important information could be obtained which would have application to satellite lifetime prediction, determination of properties of the upper atmosphere, and scientific information on the interaction of high speed molecules with surfaces (the gas surface interaction). These experiments using the tethered satellite concept are described and would measure the following variables: angle of attack, surface roughness, and flow properties.
    Keywords: AERODYNAMICS
    Type: UAH(NASA Workshop on the Use of a Tethered Satellite System; p 151-155
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  • 16
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    Publication Date: 2011-08-17
    Description: The integral representations approach, for the solution of the Navier-Stokes equations is discussed as well as experience in its development and in applying available finite-difference and finite-element techniques to the treatment of three-dimensional problems, and the computation of turbulent flow. The magnitude of efforts required to develop turbulence models and three-dimensional algorithms indicates that the computational fluid dynamics research must have a broad base. Broader access to modern computing facilities that are in existence within NASA should be promoted for active researchers not directly affiliated with that agency.
    Keywords: AERODYNAMICS
    Type: NASA. Ames Res. Center Future Computer Requirements for Computational Aerodynamics; p 221-227
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  • 17
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    Publication Date: 2011-08-17
    Description: In their most general form, the Reynolds averaged conservation equations result from ensemble or time averages of the instantaneous Navier-Stokes equations or their compressible counterparts. For these averaging processes to be consistent, the averaging time period must exceed the periods identified with the largest time scales of the turbulence, and yet be shorter than the characteristic times of the flow field. With these equations long period variations in the flow fields are deterministic, provided initial conditions are known. The average dependent variables are sufficiently smooth to be resolvable by finite difference techniques consistent with the size and speed of modern computers.
    Keywords: AERODYNAMICS
    Type: Future Computer Requirements for Computational Aerodynamics; p 239-247
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  • 18
    Publication Date: 2011-08-17
    Description: Technical and economic reasons for accelerating the maturation of the discipline of computational aerodynamics include the cost of conducting the experiments required to provide the empirical data base for new aeronautical vehicles and the limitations in test facilities (Reynolds number, wall and support interferences, aeroelastic distortions, real-gas effects, etc.) for simulating the full-scale vehicle environment. General purpose computers do not have the necessary capability for the next stage of development. Solution of the three dimensional Reynolds averaged Naiver-Stokes equations in a short time to be practical for design purposes will require 40 times the power of current supercomputers. However, it is feasible to construct a special purpose processor that will meet these requirements to enhance the nation's aerodynamic design capability in the 1980's.
    Keywords: AERODYNAMICS
    Type: Future Computer Requirements for Computational Aerodynamics; p 5-30
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  • 19
    Publication Date: 2011-08-17
    Description: The heat transfer to the stagnation point of an ablating carbonaceous heat shield, where both the gas-phase boundary layer and the heterogeneous surface reactions are not in chemical equilibrium, is examined. Specifically, the nonequilibrium changes in the mass fraction profiles of carbon species calculated for frozen flow are studied. A set of equations describing the steady-state, nonequilibrium laminar boundary layer in the axisymmetric stagnation region, over an ablating graphite surface, is solved, with allowance for the effects of finite rate of carbon vaporization.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 16; July 197
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  • 20
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    Publication Date: 2011-08-17
    Description: The difficulty of treating the perturbation of transonic flow, during which shock waves change position, can be overcome by using a distorted coordinate system in which the locations of all shock waves do not change; the distortion is found as part of the solution. This device leads to a relation that allows a range of flows, with differing shock locations, to be related algebraically to two known 'calibration' flows. Results for flows around finite wings, including those with multiple, intersecting shock waves, are presented. A typical computing time for such examples is 0.3 sec on a CDC 7600 computer.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 16; July 197
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  • 21
    Publication Date: 2011-08-18
    Description: Previously cited in issue 18, p. 726, Accession no. A78-41866
    Keywords: AERODYNAMICS
    Type: (ISSN 0021-8669)
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  • 22
    Publication Date: 2011-08-18
    Description: Previously cited in issue 12, p. 1851, Accession no. A82-27106
    Keywords: AERODYNAMICS
    Type: (ISSN 0022-4560)
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  • 23
    Publication Date: 2011-08-18
    Description: Previously cited in issue 19, p. 2971, Accession no. A82-39113
    Keywords: AERODYNAMICS
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  • 24
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 07, p. 863, Accession no. A83-21011
    Keywords: AERODYNAMICS
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  • 25
    Publication Date: 2011-08-18
    Description: Previously cited in issue 07, p. 864, Accession no. A83-21022
    Keywords: AERODYNAMICS
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  • 26
    Publication Date: 2011-08-18
    Description: Previously cited in issue 07, p. 965, Accession no. A82-19777
    Keywords: AERODYNAMICS
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  • 27
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 17, p. 2878, Accession no. A81-39001)
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  • 28
    Publication Date: 2011-08-17
    Description: In the present study, problems of laminar and turbulent two-dimensional flow of a viscous compressible fluid near the trailing edge of a thin flat plate are considered. The complete set of Navier-Stokes equations is solved by the finite-difference method of MacCormack (MacCormack and Baldwin, 1975). It is an explicit, predictor-corrector, time-splitting method of second order acuracy. The computational mesh employed has sufficient resolution for all the characteristic lengths suggested by theory. In the laminar case, the present results are compared with the triple deck solution of Daniels (1974). This comparison indicates that the asymptotic triple deck theory for supersonic trailing edge flow is accurate within five percent for Reynolds numbers greater than 1000. In the turbulent case, the Prandtl-Van Driest-Clauser algebraic eddy viscosity model is used. The numerical results show that the region of upstream influence is approximately of the order of the boundary layer thickness. The solutions for skin-friction, pressure and wake center-line velocity are presented.
    Keywords: AERODYNAMICS
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  • 29
    Publication Date: 2011-08-17
    Description: The analysis concerns the alterations produced when small amplitude disturbances, including entropy and vorticity disturbances, are imposed on steady potential flows. For the most general nonacoustic incident distortion field that can be imposed on the uniform upstream flow, it is shown that the perturbation velocity at any point of the resulting unsteady compressible and vortical flow consists of a part that is a known function of the imposed upstream distortion field and the mean flow variables and a potential part that can be found by solving a linear inhomogeneous wave equation with a dipole-type source term whose strength is a known function of the imposed upstream distortion field. The theory is applied to the unsteady flow past a corner, and a closed-form analytical solution is found.
    Keywords: AERODYNAMICS
    Type: Journal of Fluid Mechanics; 89; Dec. 13
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  • 30
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    Publication Date: 2011-08-17
    Description: Experimental results on the Reynolds number influence on the leeside flowfield of planar delta wings at supersonic speeds are presented. Wind tunnel experiments on two delta wing models with straight and sharp leading edges at freestream Mach number of 2.5 and 3.5 and angle of attack between 1 deg and 12.5 deg were carried out. The cross-sectional shape was triangular and the relative height was 0.25. The flow types investigated were to the left and right of the Stanbrook-Squire boundary. Under leading-edge separation conditions, the vortex position and intensity, and thus the suction pressure, vary with Re while the flow type remains nearly unchanged. In the region of separation with embedded shock, Re affects not only the shape of the separation bubble and pressure level near the leading edge but also the type of flow. At sufficiently high Re the flow type of separation with shock changes to one with shock-induced separation.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 16; Dec. 197
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  • 31
    Publication Date: 2011-08-17
    Description: Linearized theory is used to predict the unsteady flow in a supersonic cascade with subsonic axial flow velocity. A closed-form analytical solution is obtained by using a double application of the Wiener-Hopf technique. Although numerical and semianalytical solutions of this problem have already appeared in the literature, this paper contains the first completely analytical solution. It has been stated in the literature that the blade source should vanish at the infinite duct resonance condition. The present analysis shows that this does not occur. This apparent discrepancy is explained in the paper.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 16; Dec. 197
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  • 32
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 21, p. 3614, Accession no. A81-44900)
    Keywords: AERODYNAMICS
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  • 33
    Publication Date: 2011-08-17
    Description: Boundary-layer shape measurements at the engine inlet on four different hypersonic aircraft forebody designs (with no engine on the forebody) are reported. The measurements provide a qualitative assessment of the effectiveness of various forebody geometries as engine inlet precompression surfaces. The designs, tested in a hypersonic tunnel at Mach 6 and a nominal freestream Reynolds number of 30,500,000, included a semiconical forebody, a configuration similar to a slab delta wing, a conical nose blended into a flat surface, and a conical, complex forebody shape. Boundary layer height as a function of forebody compression is shown for each design.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 15; Jan. 197
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  • 34
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    Publication Date: 2011-08-17
    Description: The indicial method for calculating flutter derivatives for two-dimensional airfoils at transonic speeds is discussed, with particular attention given to the effect of a moving shock on the flow variables in the indicial method. An expression for the pressure coefficient is developed on the basis of an explicit treatment of the shock motion; the pressure distribution may then be calculated for general oscillations through use of the indicial method. Explicit inclusion of the shock motion is not necessary if only the lift and pitching moment coefficients are desired.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 16; June 197
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  • 35
    Publication Date: 2011-08-17
    Description: Various measurements were made to determine the temperature and attitude of the gondola and the status of primary power and control equipment. Bead thermistors were used to measure temperatures at selected points throughout the gondola. A two-axis magnetometer and a two-axis pendulum were used to measure gondola attitude. Voltage and current measurements indicated the status of the primary power sources and associated power converters.
    Keywords: AERODYNAMICS
    Type: NASA. Goddard Space Flight Center STRATCOM 8 Data Workshop and Suppl.; p 24-31
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  • 36
    Publication Date: 2011-08-17
    Description: The STRATCOM (STRATospheric COMposition) is a long term multipurpose program for integrated, correlated measurements of stratospheric parameters related to composition, thermodynamics, and radiative balance. Balloon 8-b, carrying a solar-pointing grating infrared spectrometer, two CO2 thermal emission radiometers and two in-situ air temperature sensors was launched at 1251 MST on 28 September 1977 to float at an altitude of 39 km from 1521 MST with the instruments making measurements at that altitude through the time of sunset at 1822 MST. Balloon 8-a lifted a payload consisting of four UV filter photometers, two UV spectrometers, two chemiluminescent ozonesondes, dasibi ozone monitor, 14 tube cryogenic sampler, two aluminum oxide H2O sensors, four air temperature sensors, atmospheric pressure sensor, infrared and visible pyranometers, downward-looking camera, blunt-kryton lamp-Gerdien condenser probe, three component anemometer, balloon apex-plate payload and three parachute-borne dropsondes.
    Keywords: AERODYNAMICS
    Type: NASA. Goddard Space Flight Center STRATCOM 8 Data Workshop and Suppl.; p 10-23
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  • 37
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 12, p. 1923, Accession no. A81-29496)
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  • 38
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 07, p. 963, Accession no. A82-19203)
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  • 39
    Publication Date: 2011-08-18
    Description: Previously cited in issue 15, p. 2120, Accession no. A75-33931
    Keywords: AERODYNAMICS
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  • 40
    Publication Date: 2011-08-18
    Description: Previously cited in issue 06, p. 800, Accession no. A82-17899
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  • 41
    Publication Date: 2011-08-18
    Description: Previously cited in issue 06, p. 797, Accession no. A82-17812
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  • 42
    Publication Date: 2011-08-18
    Description: An algorithm for generating computational grids about arbitrary three-dimensional bodies is developed. The elliptic partial differential equation (PDE) approach developed by Steger and Sorenson and used in the NASA computer program GRAPE is extended from two to three dimensions. Forcing functions which are found automatically by the algorithm give the user the ability to control mesh cell size and skewness at boundary surfaces. This algorithm, as is typical of PDE grid generators, gives smooth grid lines and spacing in the interior of the grid. The method is applied to a rectilinear wind-tunnel case and to two body shapes in spherical coordinates.
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  • 43
    Publication Date: 2011-08-18
    Description: Swept wings designed for laminar flow control exhibit both centrifugal and crossflow instabilities which produce streamwise vortices that can lead to early transition from laminar to turbulent flow in the presence of Tollmien-Schlichting waves. This paper outlines an iterative algorithm for generation of an orthogonal, curvilinear, coordinate grid following the streamlines of the three-dimensional viscous flow over a swept, concave surface. The governing equations for the metric tensor are derived from the Riemann-Christoffel tensor for an Euclidian geometry. Unit vectors along streamline, normal and binormal directions are determined. The governing equations are not solved directly, but are employed only as compatibility equations. The scale factor for the streamline coordinate is obtained by an iterative integration scheme on a 200 x 100 x 5 grid, while the other two scale factors are determined from definitions. Sample results are obtained which indicate that the compatibility equation error decreases linearly with grid step size. Grids smaller than 200 x 100 x 5 are found to be inadequate to resolve the grid curvature.
    Keywords: AERODYNAMICS
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  • 44
    Publication Date: 2011-08-18
    Description: Previously cited in issue 17, p. 2675, Accession no. A82-35195
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 20; 926-934
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  • 45
    Publication Date: 2011-08-18
    Description: Prandtl (1946) has concluded that for yawed laminar incompressible flows the streamwise flow is independent of the spanwise flow. However, Ashkenas and Riddell (1955) have reported that for turbulent flow the 'independence principle' does not apply to yawed flat plates. On the other hand, it was also found that this principle may be applicable to many turbulent flows. As the sweep angle is increased, a sweep angle is reached which defines the interval over which the 'independence principle' is valid. The results obtained in the present investigation indicate the magnitude of the critical angle for subsonic turbulent flow over a swept rearward-facing step.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 21; 1603
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  • 46
    Publication Date: 2011-08-18
    Description: A rapid computation of a sequence of transonic flow solutions has to be performed in many areas of aerodynamic technology. The employment of low-cost vector array processors makes the conduction of such calculations economically feasible. However, for a full utilization of the new hardware, the developed algorithms must take advantage of the special characteristics of the vector array processor. The present investigation has the objective to develop an efficient algorithm for solving transonic flow problems governed by mixed partial differential equations on an array processor.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 21; 1601-160
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  • 47
    Publication Date: 2011-08-18
    Description: The solution of the time-dependent, Reynolds-averaged, Navier-Stokes equations for unsteady, interacting flows by finite-difference algorithms is discussed. Specific examples include (1) unsteady transonic flow over a thick biconvex airfoil, (2) determination of buffet boundaries for a transonic lifting airfoil, (3) the simulation of aileron buzz and (4) dynamic stall. Algorithms considered include explicit methods, mixed (or hybrid) methods, and fully implicit methods. Consideration of time scales for computational stability, computational accuracy, and physical accuracy and the use of time-dependent adaptive meshing to realize computational efficiency are also discussed.
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  • 48
    Publication Date: 2011-08-18
    Description: The present conference covers topics concerning the measurement and calculation of interactive flows, together with problems posed by subsonic and transonic wings, missiles, and ships. Discussions are presented on the time-dependent finite difference simulation of unsteady interactive flows, Navier-Stokes equation methods, numerical solutions for spatially periodic boundary layers, the application of unsteady laminar tripple deck theory to viscous-inviscid interaction, the coupling of boundary layer and Euler equation solutions, and viscous-inviscid flow interactions. Also discussed are leading and trailing edge flows, three-dimensional wing flows, small disturbance calculations including entropy corrections, an inviscid computational method for tactical missiles, and boundary layer and flow separation characteristics of bodies of revolution at incidence.
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  • 49
    Publication Date: 2011-08-18
    Description: A single-component, computer-operated, three dimensional traversing laser Doppler velocimetry system was designed and constructed for a supersonic wind tunnel. The model was a 10 deg compression corner, providing an example of laminar boundary layer separation. Static pressure data and color schlieren photographs were taken. The Mach number was 2.42 and the Reynolds number was 213,000. The flow was seeded with submicron sized oil droplets. The trend of decreasing upstream influence with increasing Reynolds number was confirmed. Mean velocity profiles provided experimental evidence of reversed flow. Points of separation and reattachment were consistent with those determined by schlieren and pressure scans. The flow was of the laminar type until downstream of reattachment. Individual mean velocity and turbulence profiles, as well as velocity histograms are presented.
    Keywords: AERODYNAMICS
    Type: Experiments in Fluids (ISSN 0723-4864); 1; 4, 19
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  • 50
    Publication Date: 2011-08-18
    Description: An evaluation of the transonic-wing-analysis computer code TWING is presented. TWING utilizes a fully implicit, approximate-factorization iteration scheme to solve the full-potential equation in conservative form. A numerical elliptic-solver grid-generation scheme is used to generate the required finite-difference mesh. Several wing configurations have been analyzed, and comparisons of computed results have been made with available experimental data. Results indicate that the code is robust, accurate (when significant viscous effects are not present), and efficient. TWING generally produces solutions an order of magnitude faster than other conservative, full-potential codes using successive-line overrelaxation. The present method is applicable to a wide range of isolated wing configurations, including high-aspect-ratio transport wings and low-aspect-ratio, high-sweep, fighter configurations.
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  • 51
    Publication Date: 2011-08-18
    Description: Murman's fully conservative mixed type finite-difference operators are first modified. A special sonic point operator with an iterative damping term is introduced which helps the convergence and does not affect the spatial conservative differences. Reliable calculations with second order supersonic schemes are obtained using two sonic operators, the regular sonic point operator followed by a first order supersonic scheme. Also, shock point operator is shown to be equivalent to fitting a locally normal shock terminating the supersonic region. The potential calculations are then modified to account for the non-isentropic jump conditions using a simple shock fitting procedure based on Prandtl relation. The entropy increase across the shock is calculated in terms of the Mach number upstream of the shock and the effect of the generated vorticity is estimated via Crocco relation. Different examples are calculated and extensions to the full potential equation are discussed.
    Keywords: AERODYNAMICS
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  • 52
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    Publication Date: 2011-08-18
    Description: Numerical simulations of the time-dependent, Reynolds-averaged, Navier-Stokes equations, employing a two-equation turbulence model, are presented and compared with measurements from a series of trailing edge experiments at transonic Mach numbers. The test flows include an asymmetric flow with no separation, an asymmetric flow with a small region of separation and a symmetric flow with a large shock-wave induced separated zone. Comparisons are made for mean surface quantities as well as for mean and fluctuating flow-field quantities. For the trailing-edge flows with little or no separation, the solutions correctly predict all the major features of the flow field. Treatment of the viscous-inviscid interaction was found to be important for predicting these test cases. Two-equation eddy-viscosity turbulence models were found to be adequate for these flows. However, for the shock-wave induced separation case, these turbulence models were inadequate to predict this flow field. Modifications of the turbulence model to correct these deficiencies are discussed.
    Keywords: AERODYNAMICS
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  • 53
    Publication Date: 2011-08-18
    Description: Previously cited in issue 15, p. 2343, Accession no. A82-31925
    Keywords: AERODYNAMICS
    Type: (ISSN 0021-8669)
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  • 54
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 15, p. 2343, Accession no. A82-31931
    Keywords: AERODYNAMICS
    Type: (ISSN 0001-1452)
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  • 55
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 15, p. 2348, Accession no. A82-31974)
    Keywords: AERODYNAMICS
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  • 56
    Publication Date: 2011-08-18
    Description: Previously cited in issue 15, p. 2347, Accession no. A82-31971
    Keywords: AERODYNAMICS
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  • 57
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 07, p. 965, Accession no. A82-19783
    Keywords: AERODYNAMICS
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  • 58
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 06, p. 796, Accession no. A82-17785
    Keywords: AERODYNAMICS
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  • 59
    Publication Date: 2011-08-18
    Description: Previously cited in issue 17, p. 2880, Accession no. A81-39057
    Keywords: AERODYNAMICS
    Type: (ISSN 0022-4560)
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  • 60
    Publication Date: 2011-08-18
    Description: Previously cited in issue 20, p. 3457, Accession no. 81-43146
    Keywords: AERODYNAMICS
    Type: (ISSN 0021-8669)
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  • 61
    Publication Date: 2011-08-18
    Description: The behavior of a narrow cross-section wedge wing moving at a high Mach number and subjected to an angle of attack changing exponentially with time is investigated. This type of wedge wing is commonly employed as a lifting surface in hypersonic vehicles. The time history of wall shear, heat transfer, displacement thickness, and viscous induced pressure are determined. Results show that for the same change in angle of attack, the flow attains the final steady state much faster when the change is exponential than when the change is made impulsively. In addition, the unsteady character of the flow is primarily confined to the initial stages of the change in the angle of attack.
    Keywords: AERODYNAMICS
    Type: Acta Mechanica; 47; 1-2,; 1983
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  • 62
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 08, p. 1181, Accession no. A82-22096)
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  • 63
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-10011)
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  • 64
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 22, p. 3806, Accession no. A81-45890)
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  • 65
    Publication Date: 2011-08-18
    Description: (Previously cited in issue 16, p. 2685, Accession no. A81-37539)
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  • 66
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 383-406
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  • 67
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 1; p 337-34
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  • 68
    Publication Date: 2011-08-18
    Description: Previously cited in issue 10, p. 1539, Accession no. A82-24653
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 20; 513-517
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  • 69
    Publication Date: 2011-08-18
    Description: Previously cited in issue 05, p. 586, Accession no. A83-16745
    Keywords: AERODYNAMICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 20; 524-530
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  • 70
    Publication Date: 2016-06-07
    Description: Skin temperatures, shearing forces, surface static pressures, and boundary layer pitot pressures and total temperatures were measured on a hollow cylinder 3.04 meters long and 0.437 meter in diameter mounted beneath the fuselage of the YF-12A airplane. The data were obtained at a nominal free stream Mach number of 3.0 and at wall-to-recovery temperature ratios of 0.66 to 0.91. The free stream Reynolds number had a minimal value of 4.2 million per meter. Heat transfer coefficients and skin friction coefficients were derived from skin temperature time histories and shear force measurements, respectively. Boundary layer velocity profiles were derived from pitot pressure measurements, and a Reynolds analogy factor of 1.11 was obtained from the measured heat transfer and skin friction data. The skin friction coefficients predicted by the theory of van Driest were in excellent agreement with the measurements. Theoretical heat transfer coefficients, in the form of Stanton numbers calculated by using a modified Reynolds analogy between skin friction and heat transfer, were compared with measured values. The measured velocity profiles were compared to Coles' incompressible law-of-the-wall profile.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 259-286
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  • 71
    Publication Date: 2016-06-07
    Description: In-flight measurements of boundary layer and skin friction data were made on YF-12 airplanes for Mach numbers between 2.0 and 3.0. Boattail pressures were also obtained for Mach numbers between 0.7 and 3.0 with Reynolds numbers up to four hundred million. Boundary layer data measured along the lower fuselage centerline indicate local displacement and momentum thicknesses can be much larger than predicted. Skin friction coefficients measured at two of five lower fuselage stations were significantly less than predicted by flat plate theory. The presence of large differences between measured boattail pressure drag and values calculated by a potential flow solution indicates the presence of vortex effects on the upper boattail surface. At both subsonic and supersonic speeds, pressure drag on the longer of two boattail configurations was equal to or less than the pressure drag on the shorter configuration. At subsonic and transonic speeds, the difference in the drag coefficient was on the order of 0.0008 to 0.0010. In the supersonic cruise range, the difference in the drag coefficient was on the order of 0.002. Boattail drag coefficients are based on wing reference area.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 227-258
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  • 72
    Publication Date: 2016-06-07
    Description: Aft-facing step base pressure flight data were obtained for three step heights for nominal transonic Mach numbers of 0.80, 0.90, and 0.95, and for supersonic Mach numbers of 2.2, 2.5, and 2.8 with a Reynolds number, based on the fuselage length ahead of the step, of about 10 to the 8th power. Surface static pressures were measured ahead of the step, behind the step, and on the step face (base), and a boundary layer rake was used to obtain boundary layer reference conditions. A comparison of the data from the present and previous experiments shows the same trend of increasing base pressure ratio (decreasing drag) with increasing values of momentum thickness to step height ratios. However, the absolute level of these data does not always agree at the supersonic Mach numbers. For momentum thickness to height ratios near 1.0, the differences in the base pressure ratios appear to be primarily a function of Reynolds number based on the momentum thickness. Thus, for Mach numbers above 2, the data analyzed show that the base pressure ratio decreases (drag increases) as Reynolds number based on momentum thickness increases for a given momentum thickness and step height.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 201-226
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  • 73
    Publication Date: 2016-06-07
    Description: The response of terminal-shock position and static pressures in the subsonic duct of a YF-12 aircraft flight-hardware inlet to perturbations in simulated engine corrected airflow were obtained with and without inlet control. Frequency response data, obtained with inlet controls inactive, indicated the general nature of the inherent inlet dynamics, assisted in the design of controls, and provided a baseline reference for responses with active controls. All the control laws were implemented by means of a digital computer that could be programmed to behave like the flight inlet's existing analog control. The experimental controls were designed using an analytical optimization technique. The capabilities of the controls were limited primarily by the actuation hardware. The experimental controls provided somewhat better attenuation of terminal shock excursions than did the YF-13 inlet control. Controls using both the forward and aft bypass systems also provided somewhat better attenuation than those using just the forward bypass. The main advantage of using both bypasses is in the greater control flexibility that is achieved.
    Keywords: AERODYNAMICS
    Type: NASA. Dryden Flight Res. Center YF-12 Experiments Symp., Vol. 1; p 157-192
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  • 74
    Publication Date: 2016-06-07
    Description: Aircraft parameters and physiological parameters most indicative of crew workload were investigated. Recommendations were used to form the basis for a continuing study in which variations of the interval between heart beats are used as a measure of nonphysical workload. Preliminary results are presented and current efforts in further defining this physiological measure are outlined.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 121-134
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  • 75
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    Publication Date: 2016-06-07
    Description: A true gust velocity measuring system designed to alleviate complications resulting from airframe flexibility and from the high-speed, high-temperature environment of supersonic cruise aircraft was evaluated on a YF-12 airplane. The system uses fixed vanes on which airflow direction changes produce differential pressure variations that are measured. Airframe motions, obtained by postflight integration of recorded angular rate and linear acceleration data, are removed from the flow angle data. An example of turbulence data obtained at high-altitude, supersonic flight conditions is presented and compared with previous high-altitude turbulence measurements obtained with subsonic aircraft and with turbulence criteria contained in both military and civil design specifications for supersonic cruise vehicles. Results of these comparisons indicate that the YF-12 turbulence sample is representative of turbulence present in the supersonic cruise environment.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 135-154
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  • 76
    Publication Date: 2016-06-07
    Description: The altitude hold mode of the YF-12A airplane was modified to include a high-pass-filtered pitch rate feedback along with optimized inner loop altitude rate proportional and integral gains. An autothrottle control system was also developed to control either Mach number or KEAS at the high-speed flight conditions. Flight tests indicate that, with the modified system, significant improvements are obtained in both altitude and speed control, and the combination of altitude and autothrottle hold modes provides the most stable aircraft platform thus far demonstrated at Mach 3 conditions.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 97-119
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  • 77
    Publication Date: 2016-06-07
    Description: Ventral fin loads, expressed as normal force coefficients, bending moment coefficients, and torque coefficients, were measured during flight tests of a YF-12A airplane. Because of the proximity of the ventral fin to the ailerons, the aerodynamic loads presented were the result of both sideslip loads and aileron crossflow loads. Aerodynamic data obtained from strain gage loads instrumentation and some flight pressure measurements are presented for several Mach numbers ranging from 0.70 to 2.00. Selected wind tunnel data and results of linear theoretical aerodynamic calculations are presented for comparison.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 73-91
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  • 78
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    Publication Date: 2016-06-07
    Description: The history of NASA's interest in supersonic research and the agency's contribution to the development of the YF 12 aircraft is reviewed as well as the program designed to use that aircraft as a test bed for supersonic cruise research. Topics cover elements of the program, project organization, and major accomplishments.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 3-25
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  • 79
    Publication Date: 2016-06-07
    Description: The use of calibrated strain gages to measure wing loads on the YF-12A airplane is discussed as well as structural configurations relative to the thermal environment and resulting thermal stresses. A thermal calibration of the YF-12A is described to illustrate how contaminating thermal effects can be removed from loads equations. The relationship between ground load calibrations and flight measurements is examined for possible errors, and an analytical approach to accommodate such errors is presented.
    Keywords: AERODYNAMICS
    Type: YF-12 Experiments Symp., Vol. 1; p 47-72
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  • 80
    Publication Date: 2016-06-07
    Description: A brief overview of the highlights of NASA's wake vortex minimization program is presented. The significant results of this program are summarized as follows: (1) it is technically feasible to reduce significantly the rolling upset created on a trailing aircraft; (2) the basic principles or methods by which reduction in the vortex strength can be achieved have been identified; and (3) an analytical capability for investigating aircraft vortex wakes has been developed.
    Keywords: AERODYNAMICS
    Type: CTOL Transport Technol., 1978; p 757-771
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  • 81
    Publication Date: 2016-06-07
    Description: The problem of obtaining accurate estimates of suction requirements on swept laminar flow control wings was discussed. A fast accurate computer code developed to predict suction requirements by integrating disturbance amplification rates was described. Assumptions and approximations used in the present computer code are examined in light of flow conditions on the swept wing which may limit their validity.
    Keywords: AERODYNAMICS
    Type: CTOL Transport Technol. 1978; p 375-394
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  • 82
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    Publication Date: 2016-06-07
    Description: Application of laminar flow control technology to future CTOL long range transport aircraft was considered. Topics covered include: (1) airfoil development and test; (2) development and improvement of design methods; (3) evaluation of leading edge contamination; and (4) laminar flow control system definition and concept evaluation.
    Keywords: AERODYNAMICS
    Type: CTOL Transport Technol., 1978; p 349-356
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  • 83
    Publication Date: 2017-10-02
    Description: Spanwise blowing over the wing and canard of a 1:35 model of a close-coupled-canard fighter-airplane configuration (similar to the Kfir-C2) was investigated experimentally in low-speed flow. Tests were conducted at airspeeds of 30 m/sec (Reynolds number of 1.8 x 10 to the 5th power based on mean aerodynamic chord) with angle-of-attack sweeps from -8 deg to 60 deg, and yaw-angle sweeps from -8 deg to 36 deg at fixed angles of attack 0 deg, 10 deg, 20 deg, 25 deg, 30 deg, and 35 deg. Significant improvement in lift-curve slope, maximum lift, drag polar and lateral/directional stability was found, enlarging the flight envelope beyond its previous low-speed/maximum-lift limit. In spite of the highly swept (60 deg) leading edge, the efficiency of the lift augmentation by blowing was relatively high and was found to increase with increasing blowing momentum on the close-coupled-canard configuration. Interesting possibilities of obtaining much higher efficiencies with swirling jets were indicated.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Vortical Type Flows in Three Dimensions; 26 p
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  • 84
    Publication Date: 2017-10-02
    Description: The importance of leading edge vortical flows, which occur near and interact with neighboring surfaces, is stressed. Research in this area conducted or sponsored by the NASA Langley Research Center since 1978 is surveyed. Particular attention is given to the cumulative results of a number of theoretical and experimental studies. It is noted that these studies have been carried out in order to understand and use this kind of flow. Much of the work has been devoted to improving the lift-to-drag ratio and pitch characteristics for wings in this flow, although work has also been done on examining the unsteady and lateral characteristics.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Vortical Type Flows in Three Dimensions; 32 p
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  • 85
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    Publication Date: 2017-10-02
    Description: This lecture consists of three parts, in which discussions are presented of the current state of development of transonic or supercritical airfoils designed for fully turbulent boundary layers on the surfaces, previous research on subcritical airfoils designed to achieve laminar boundary layers on all or parts of the surfaces, and current research on supercritical airfoils designed to achieve laminar boundary layers. In the first part the use of available two dimensional computer codes in the development of supercritical airfoils and the general trends in the design of such airfoils with turbulent boundary layers are discussed. The second part provides the necessary background on laminar boundary layer phenomena. The last part, which constitutes the major portion of the lecture, covers research by NASA on supercritical airfoils utilizing both decreasing pressure gradients and surface suction for stabilizing the laminar boundary layer. An investigation of the former has been recently conducted in fight using gloves on the wing panels of the U.S. Air Force F111 TACT airplane, research on the later is currently being conducted in a transonic wind tunnel which has been modified to greatly reduce the stream turbulence and noise levels in the tests section.
    Keywords: AERODYNAMICS
    Type: AGARD Spec. Course on Subsonic(Transonic Aerodyn. Interference for Aircraft; 9 p
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  • 86
    Publication Date: 2017-10-02
    Description: A numerical investigation of the two-dimensional recirculation zone formed between a rear-ward facing step and a transverse hydrogen jet in a supersonic flow is presented. Calculations were made using an elliptic flow computer code with a time-relaxation finite difference integration algorithm. Cases were examined for jet static pressures between 2 and 5 times mainstream with jets located 3 to 7 step heights downstream of the step. Nominal mainstream flow conditions were Mach 2.4 air at 1 atm pressure and 1000K (1800R) static temperature. Results in the form of mean properties in the recirculation zone and residence time are presented. Calculations of the decay of hydrogen mass from the steady state are presented for selected cases. The combustion potential for each case is assessed by comparison of computed conditions in the recirculation zone with the results from a well-stirred reactor theory.
    Keywords: AERODYNAMICS
    Type: APL The 20th JANNAF Combust. Meeting, Vol. 1; p 635-652
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  • 87
    Publication Date: 2017-10-02
    Description: The vortex-filament method was applied to the simulation of vortex breakdown. The principal vortex region was represented by multiple filaments, and an axial velocity component was induced by a spiral winding of the filaments. An accuracy check was performed for a cylindrical swirling flow with simple analytical expressions for the axial and theta velocities. The result suggests that the flow field can be simulated to any accuracy by increasing the number of filaments. An axisymmetric-type vortex breakdown was simulated, with experimental data serving as upstream conditions. The calculated axial- and theta-velocity contours show the breakdown of the vortex, including a rapid change in the vortex core, followed axially by a recovery zone and then a second breakdown. When three dimensional initial data are used the second breakdown appears to be of the spiral type in correspondence with experimental observations. The present method can easily be used to simulate other types of vortex breakdown or other vortex flows with axial velocity.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Vortical Type Flows in Three Dimensions; 13 p
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  • 88
    Publication Date: 2017-10-02
    Description: A method is described for incorporating line vortices into the three dimensional compressible potential flow equation. A modified Biot-Savart law is used to compute a vortical velocity field, which is added to the gradient of the potential to form a total velocity. A rapidly converging approximate factorization (AFZ) scheme is then used to compute a potential such that the modified potential flow equation as well as the appropriate boundary conditions, based on total velocity, are satisfied. As part of a coupled iteration procedure, the positions of the line vortices are computed so that they convect with the total flow. The method is used to compute the field due to a single line vortex convecting past a wing. This represents an approximation of the effect of a canard or other lifting surface ahead of the wing, which sheds a tip vortex. It is seen that the flow field is substantially modified by the passage of the vortex. Unlike Euler equation schemes, which are also used to compute these flows, the solutions exhibit no numerical diffusion: The convected vortices retain their initial upstream width. Euler solutions, on the other hand, involve a vorticity which is numerically convected in an Eulerian frame and, unless extensive adaptive grid refinement is used they result in vortices with spread as they convect. Also, the potential flow method requires approximately two orders of magnitude less computing time and much less computer storage than the Euler methods.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Vortical Type Flows in Three Dimensions; 12 p
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  • 89
    Publication Date: 2017-10-02
    Description: Vortical flows in three dimensional configurations that are of typical interest to aerodynamicists and researchers in fluid mechanics are reviewed. A list of 10 issues was compiled to understanding complex vortical flows.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Vortical Type Flows in Three Dimensions; 31 p
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  • 90
    Publication Date: 2018-12-01
    Description: A numerical investigation of the two-dimensional recirculation zone formed between a rearward facing step and a transverse hydrogen jet in a supersonic flow is presented. Calculations were made using an elliptic flow computer code with a time-relaxation finite difference integration algorithm. Cases were examined for jet static pressures between 2 and 5 times mainstream with jets located 3 to 7 step heights downstream of the step. Nominal mainstream flow conditions were Mach 2.4 air at 1 atm pressure and 1000 K (1800 R) static temperature. Results in the form of mean properties in the recirculation zone and residence time are presented. Calculations of the decay of hydrogen mass from the steady state are presented for selected cases. The combustion potential for each case is assessed by comparison of computed conditions in the recirculation zone with the results from a well-stirred reactor theory.
    Keywords: AERODYNAMICS
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  • 91
    Publication Date: 2018-12-01
    Description: Eight turbulence-control/drag-reduction concepts under study at NASA Langley Research Center are discussed. These concepts include: slot injection, ion wind, large-eddy breakup devices, riblets, relaminarization, convex curvature, passive porous walls, and rigid wavy walls. Of these concepts, passive porous walls and small wavelength wavy walls are found to increase drag. Riblets, slot injection, and large-eddy breakup devices reduce net turbulent drag, at least for some conditions. The ion wind, relaminarization, and convex curvature studies are still in the early stages and require further work to evaluate their applicability for drag reduction.
    Keywords: AERODYNAMICS
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  • 92
    Publication Date: 2019-06-28
    Description: Wind-tunnel tests to measure unsteady aerodynamic data in the transonic region have been completed on an aspect ratio 2.0 rectangular wing with a supercritical airfoil. The geometric and structural properties of the wing are presented. (Other references contain the measured aerodynamic data.) Both measured and design airfoil coordinates are presented and compared. In addition, measured wing bending and torsional stiffness distributions and some trailing-edge flexibility influence coefficients are presented.
    Keywords: AERODYNAMICS
    Type: NASA-TM-85673 , NAS 1.15:85673
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  • 93
    Publication Date: 2019-06-28
    Description: A program called FLEXWAL for calculating wall modifications for solid, adaptive-wall wind tunnels is presented. The method used is the iterative technique of NASA TP-2081 and is applicable to subsonic and transonic test conditions. The program usage, program listing, and a sample case are given.
    Keywords: AERODYNAMICS
    Type: NASA-TM-84648 , NAS 1.15:84648
    Format: application/pdf
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  • 94
    Publication Date: 2019-06-28
    Description: The proper design of engine nacelle installations for supersonic aircraft depends on a sophisticated understanding of the interactions between the boundary layers and the bounding external flows. The successful operation of mixed external-internal compression inlets depends significantly on the ability to closely control the operation of the internal compression portion of the inlet. This portion of the inlet is one where compression is achieved by multiple reflection of oblique shock waves and weak compression waves in a converging internal flow passage. However weak these shocks and waves may seem gas-dynamically, they are of sufficient strength to separate a laminar boundary layer and generally even strong enough for separation or incipient separation of the turbulent boundary layers. An understanding was developed of the viscous-inviscid interactions and of the shock wave boundary layer interactions and reflections.
    Keywords: AERODYNAMICS
    Type: NASA-CR-186581 , NAS 1.26:186581
    Format: application/pdf
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  • 95
    Publication Date: 2017-10-02
    Description: Recent progress in vortex-control applications for alleviating the adverse consequences of three dimensional separation and vortical interactions on slender body/swept wing configurations is reported. Examples include helical separation trip to alleviate the side force due to forebody vortex asymmetry; hinged strakes to avoid vortex breakdown effects; compartmentation of swept leading edge separation to delay the pitch-up instability; under wing vortex trip and vortex trip and vortex flaps for drag reduction at high lift; and an apex-flap trimmer to fully utilize the lift capability of trailing-edge flaps for take off and landing of delta wings. Experimental results on generic wind-tunnel models are presented to illustrate the vortex-management concepts involved and to indicate their potential for enhancing the subsonic aerodynamics of supersonic-cruise type vehicles.
    Keywords: AERODYNAMICS
    Type: AGARD Aerodyn. of Vortical Type Flows in Three Dimensions; 14 p
    Format: text
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  • 96
    Publication Date: 2017-10-02
    Description: Transition and fluctuating surface pressure data were acquired on a 10 degree included angle cone, using the same instrumentation and technique over a wide range of Mach and Reynolds numbers in 23 wind tunnels and in flight. Transition was detected with a traversing pitot pressure probe in contact with the surface. The surface pressure fluctuations were measured with microphones set flush in the cone surface. Good correlation of end of transition Reynolds number Re (sub T) was obtained between data from the lower disturbance wind tunnels and flight up to a boundary layer edge Mach number, M (sub e) = 1.2. Above M (sub e) = 1.2, however, this correlation deteriorates, with the flight Re (sub T) being 25 to 30% higher than the wind tunnel Re (sub T) at M (sub e) = 1.6. The end of transition Reynolds number correlated within + or - 20% with the surface pressure fluctuations. Broad peaks in the power spectral density distributions indicated that Tollmien-Schlichting waves were the probable cause of transition in flight and in some of the wind tunnels.
    Keywords: AERODYNAMICS
    Type: AGARD Ground(Flight Test Tech. and Correlation; 25 p
    Format: text
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  • 97
    Publication Date: 2018-12-01
    Description: The importance of leadingedge vortical flows, which occur near and interact with neighboring surfaces, is stressed. Research in this area conducted or sponsored by the NASA Langley Research Center since 1978 is surveyed. Particular attention is given to the cumulative results of a number of theoretical and experimental studies. It is noted that these studies have been carried out in order to understand and use this kind of flow. Much of the work has been devoted to improving the lift-to-drag ratio and pitch characteristics for wings in this flow, although work has also been done on examining the unsteady and lateral characteristics.
    Keywords: AERODYNAMICS
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  • 98
    Publication Date: 2019-06-28
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 495-53
    Format: text
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  • 99
    Publication Date: 2019-06-28
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 407-43
    Format: text
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  • 100
    Publication Date: 2019-06-28
    Description: Calculations were made of the effects of surface waviness on the external pressure of a supercritical airfoil at design conditions. Wave parameters varied include amplitude, wavelength, phase, and number of cycles. Effects of single and multiple waves are calculated at various chordwise locations. General trends of surface waviness effects on pressure distribution are determined and these solutions are reported. Contour deviations are imposed on the upper surface of the airfoil. Results are presented in a manner designed to facilitate ready comparison with the ideal contour static pressure distribution.
    Keywords: AERODYNAMICS
    Type: NASA-TM-85705 , NAS 1.15:85705
    Format: application/pdf
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