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  • METEOROLOGY AND CLIMATOLOGY  (15)
  • GEOPHYSICS  (9)
  • AERODYNAMICS  (7)
  • STRUCTURAL MECHANICS
  • 1990-1994  (36)
  • 1
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    Control of boundary layer transition location and plate vibration in the presence of an external acoustic field (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The experiment is aimed at controlling the boundary layer transition location and the plate vibration when excited by a flow and an upstream sound source. Sound has been found to affect the flow at the leading edge and the response of a flexible plate in a boundary layer. Because the sound induces early transition, the panel vibration is acoustically coupled to the turbulent boundary layer by the upstream radiation. Localized surface heating at the leading edge delays the transition location downstream of the flexible plate. The response of the plate excited by a turbulent boundary layer (without sound) shows that the plate is forced to vibrate at different frequencies and with different amplitudes as the flow velocity changes indicating that the plate is driven by the convective waves of the boundary layer. The acoustic disturbances induced by the upstream sound dominate the response of the plate when the boundary layer is either turbulent or laminar. Active vibration control was used to reduce the sound induced displacement amplitude of the plate.
    Keywords: STRUCTURAL MECHANICS
    Type: In: Structural dynamics: Recent advances; Proceedings of the 4th International Conference, Univ. of Southampton, United Kingdom, July 15-18, 1991 (A93-45104 18-39); p. 702-711.
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  • 2
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    VICONOPT - Program for exact vibration and buckling analysis or design of prismatic plate assemblies (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1927
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  • 3
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    Flow computations for the Space Shuttle in ascent mode using thin-layer Navier-Stokes equations (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The application of CFD techniques to the Space Shuttle ascent environment was aggressively undertaken in the wake of the Challenger accident in order to secure a major new source of aerodynamic information for both the nominal and mission-abort conditions, using Cray 2 and Cray YMP supercomputers. Due to the integrated vehicle's complexity, the 'chimera' composite grid approach, in which an overset body-conforming grid is used to represent each geometric component as well as special flow regions, was employed for the discretization process. Calculation results exhibit general agreement in both flow structure and surface pressure with the available wind tunnel and flight-test results.
    Keywords: AERODYNAMICS
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  • 4
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    Structural dynamic and aeroelastic considerations for hypersonic vehicles (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Structural dynamic and aeroelastic considerations applicable to hypersonic vehicles are discussed. Emphasis is given to aerospace plane configurations. The definition of aerothermoelasticity and the operational flight environment are reviewed, and structural dynamic and aeroelastic areas of concern are individually discussed, including vibration, landing and taxiing, propellant dynamics, acoustics, lifting surface flutter, panel flutter, control surface buzz, buffeting, gust response, and static aeroelasticity. Recent research results from all-moveable delta-wing aerolastic studies, engine inlet lip aeroelastic analysis, and studies of thermal effects on vibration frequencies, aerodynamic heating effects on flutter, and active control of aeroelastic response are reviewed.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 91-1255
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  • 5
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    Geostationary earth climate sensor: Scientific utility and feasibility, phase A (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The possibility of accurate broad band radiation budget measurements from a GEO platform will provide a unique opportunity for viewing radiation processes in the atmosphere-ocean system. The CSU/TRW team has prepared a Phase 1 instrument design study demonstrating that measurements of radiation budget are practical from geosynchronous orbit with proven technology. This instrument concept is the Geostationary Earth Climate Sensor (GECS). A range of resolutions down to 20 km at the top of the atmosphere are possible, depending upon the scientific goals of the experiment. These tradeoffs of resolution and measurement repeat cycles are examined for scientific utility. The design of a flexible instrument is shown to be possible to meet the two goals: long-term, systematic monitoring of the diurnal cycles of radiation budget; and high time and space resolution studies of regional radiation features.
    Keywords: GEOPHYSICS
    Type: NASA-CR-191919 , NAS 1.26:191919
    Format: application/pdf
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  • 6
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    Implementation of wall boundary conditions for transpiration in F3D thin-layer Navier-Stokes code (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Numerical boundary conditions for mass injection/suction at the wall are incorporated in the thin-layer Navier-Stokes code, F3D. The accuracy of the boundary conditions and the code is assessed by a detailed comparison of the predictions of velocity distributions and skin-friction coefficients with exact similarity solutions for laminar flow over a flat plate with variable blowing/suction, and measurements for turbulent flow past a flat plate with uniform blowing. In laminar flow, F3D predictions for friction coefficient compare well with exact similarity solution with and without suction, but produces large errors at moderate-to-large values of blowing. A slight Mach number dependence of skin-friction coefficient due to blowing in turbulent flow is computed by F3D code. Predicted surface pressures for turbulent flow past an airfoil with mass injection are in qualitative agreement with measurements for a flat plate.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-3204 , AIAA Applied Aerodynamics Conference; Sept. 23-25, 1991; Baltimore, MD; United States
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  • 7
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    HF Doppler and VHF radar observations of upper atmospheric disturbances caused by weak cold front during winter time (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The simultaneous use of the Taiwan VHF radar and the HF Doppler sounder for remote measurement of three-dimensional winds, gravity waves, and density perturbations at mesospheric and thermospheric heights is demonstrated. A special event of atmospheric disturbances caused by propagating gravity waves excited by weak convective motions in winter time were investigated. The three-dimensional wind velocities at different heights were determined, and the frequency, horizontal wavelength, vertical wavelength, and phase velocity of the gravity waves were measured. The subtropical, low-latitude site makes the VHF radar and HF Doppler array systems unique, and the observations especially valuable for space projects dealing with low-latitude atmosphere.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: AIAA PAPER 90-0483
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  • 8
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    User manual for VICONOPT: An exact analysis and optimum design program covering the buckling and vibration of prismatic assemblies of flat in-plane loaded, anisotropic plates, with approximations for discrete supports, and transverse stiffeners (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer program which is designed for efficient, accurate buckling and vibration analysis and optimum design of composite panels is described. The capabilities of the program are given along with detailed user instructions. It is written in FORTRAN 77 and is operational on VAX, IBM, and CDC computers and should be readily adapted to others. Several illustrations of the various aspects of the input are given along the example problems illustrating the use and application of the program.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-181966 , NAS 1.26:181966
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  • 9
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    A mechanism to produce a dawn-dusk component of plasma flow during magnetic reconnection in the magnetotail (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Magnetic reconnection between antiparallel field lines in the magnetotail is generally thought to produce plasma acceleration in the earthward-tailward direction. However, measurements of the plasma velocity in the magnetotail during substorm activity sometimes reveal a dawn-dusk component of plasma flow. In this paper, we show that a dawn-dusk component of plasma acceleration may be produced during reconnection if the neutral line is not perpendicular to the magnetic field. In this case, Magnetohydrodynamic (MHD) simulations show that reconnection between antiparallel field lines will initially produce plasma acceleration that is nearly parallel to the neutral line because the magnetic tension force is not opposed by a pressure gradient force in this direction. As the magnetic field topology evolves to a steady state, the plasma flow direction rotates until it is nearly parallel to the plane that initially contained the antiparallel magnetic field lines before reconnection (hereafter referred to as the initial field plane). However, the time required to reach a steady state (typically several hundred seconds in the magnetotail region) may be greater than the time during which the reconnection process is active. Consequently, bursts of plasma flow with a dawn-dusk component may occur in the magnetotail. The initial acceleration along the neutral line depends on the angle theta (sub B) between the neutral line and the initial field plane, with the largest burst of plasma flow along the neutral line occuring when theta (s ub B) = 45 degs.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A4; p. 5869-5875
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  • 10
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    Transonic wind tunnel wall interference analysis for the Space Shuttle Launch Vehicle (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The AEDC perforated-wall boundary condition has been incorporated into the NASA Ames OVERFLOW code and has been used to calculate the tunnel flow field in the AEDC Aerodynamic Wind Tunnel (16T) over a three-percent model of the Space Shuttle Launch Vehicle. Tunnel flow-field calculations have been performed for two supersonic flow-field conditions, including one near sonic condition. Wall interference assessments and analyses have been performed by making detailed comparisons of the tunnel flow-field calculations with corresponding free-air flow-field calculations and with tunnel data from different scale models. A capability to assess wall interference at low supersonic conditions and to improve data correlations with CFD results by adding the tunnel wall boundary condition is demonstrated.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 93-0420 , AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States|; 17 p.
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