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  • AERODYNAMICS  (381)
  • 1980-1984
  • 1975-1979  (381)
  • 1970-1974
  • 1978  (381)
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  • 1980-1984
  • 1975-1979  (381)
  • 1970-1974
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  • 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
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    In:  Other Sources
    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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  • 7
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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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  • 8
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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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  • 9
    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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  • 10
    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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