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  • 1
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    Laser Doppler velocimeter multiplexer interface for simultaneous measured events (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A laser Doppler velocimeter multiplexer interface includes an event pulse synchronizer which synchronizes data pulses from events A, B, and C. Clock control is connected to receive timing information on the data pulses from the synchronizer. Displays are connected to receive clock signals from the clock control for indicating a data rate for each of the measured events A, B, and C. The display is connected to receive clock signals from the clock control to indicate a coincidence rate between data pulses for any selected combination of the measured events A, B, and C. A multiplexer receives the data pulses from the events A, B, and C and rate data from the clock control. The multiplexer has output for supplying the data pulses and rate data to a single input of a data processing system. A multiplexer control is connected to supply control signals to the multiplexer for selecting the event data pulses and the rate data for output from the multiplexer. The multiplexer control receives start signals from the pulse synchronizer and user selected inputs for desired outputs from the multiplexer.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Hypersonic shock structure with Burnett terms in the viscous stress and heat flux (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The continuum Navier-Stokes and Burnett equations are solved for one-dimensional shock structure in various monatomic gases. A new numerical method is employed which utilizes the complete time-dependent continuum equations and obtains the steady-state shock structure by allowing the system to relax from arbitrary initial conditions. Included is discussion of numerical difficulties encountered when solving the Burnett equations. Continuum solutions are compared to those obtained utilizing the Direct Simulation Monte Carlo method. Shock solutions are obtained for a hard sphere gas and for argon from Mach 1.3 to Mach 50. Solutions for a Maxwellian gas are obtained from Mach 1.3 to Mach 3.8. It is shown that the Burnett equations yield shock structure solutions in much closer agreement to both Monte Carlo and experimental results than do the Navier-Stokes equations. Shock density thickness, density asymmetry, and density-temperature separation are all more accurately predicted by the Burnett equations than by the Navier-Stokes equations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 88-2733
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    NASA TECHNICAL REPORTS
  • 3
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    Performance and power regulation characteristics of two aileron-controlled rotors and a pitchable tip-controlled rotor on the Mod-O turbine (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tests were conducted on the DOE/NASA mod-0 horizontal axis wind turbine to compare and evaluate the performance and the power regulation characteristics of two aileron-controlled rotors and a pitchable tip-controlled rotor. The two aileron-controlled rotor configurations used 20 and 38 percent chord ailerons, while the tip-controlled rotor had a pitchable blade tip. The ability of the control surfaces to regulate power was determined by measuring the change in power caused by an incremental change in the deflection angle of the control surface. The data shows that the change in power per degree of deflection angle for the tip-controlled rotor was four times the corresponding value for the 2- percent chord ailerons. The root mean square power deviation about a power setpoint was highest for the 20 percent chord aileron, and lowest for the 38 percent chord aileron.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-TM-100136 , DOE/NASA/20320-73 , E-3686 , NAS 1.15:100136
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Numerical modeling of turbulent supersonic reacting coaxial jets (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The paper considers the mixing and subsequent combustion within turbulent reacting shear layers. A computer program was developed to solve the axisymmetric Reynolds averaged Navier-Stokes equations. The numerical method integrates the Reynolds averaged Navier-Stokes equations using a finite volume approach while advancing the solution forward in time using a Runge-Kutta scheme. Three separate flowfields are investigated and it is found that no single turbulence model considered could accurately predict the degree of mixing for all three cases.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: AIAA PAPER 89-0660
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  • 5
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    Computational fluid dynamics near the continuum limit (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Two dimensional Navier-Stokes equations for a perfect gas are solved for hypersonic flow over a flat plate at Reynolds numbers ranging from continuum to the free molecule flow. In the transition flow regime, new slip boundary conditions are introduced, which reduce to the well-known slip conditions of Maxwell at small Knudsen numbers and yield the correct shear stress and heat transfer in the limiting case of free molecule flow. Comparison of the computed results with the existing experimental data and Monte Carlo calculations indicates that the continuum Navier-Stokes equations give surprisingly realistic results throughout the transition flow regime, when the new slip boundary conditions are used.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-1115
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  • 6
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    Comparison of shock structure solutions using independent continuum and kinetic theory approaches (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A vehicle traversing the atmosphere will experience flight regimes at high altitudes in which the thickness of a hypersonic shock wave is not small compared to the shock standoff distance from the hard body. When this occurs, it is essential to compute accurate flow field solutions within the shock structure. In this paper, one-dimensional shock structure is investigated for various monatomic gases from Mach 1.4 to Mach 35. Kinetic theory solutions are computed using the Direct Simulation Monte Carlo method. Steady-state solutions of the Navier-Stokes equations and of a slightly truncated form of the Burnett equations are determined by relaxation to a steady state of the time-dependent continuum equations. Monte Carlo results are in excellent agreement with published experimental data and are used as bases of comparison for continuum solutions. For a Maxwellian gas, the truncated Burnett equations are shown to produce far more accurate solutions of shock structure than the Navier-Stokes equations.
    Keywords: AERODYNAMICS
    Type: Sensing, Discrimination, and Signal Processing and Superconducting Materials and Instrumentation; Jan 12, 1988 - Jan 14, 1988; Los Angeles, CA; United States
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    NASA TECHNICAL REPORTS
  • 7
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    Fundamental problem in computing radiating flow fields with thick shock waves (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Possible reasons for the failure of the Navier-Stokes equations to yield realistic profiles of the temperature and density through the structure of a hypersonic shock wave are investigated. Models for bulk viscosity in a monatomic gas are examined which yield a realistic thickness for the shock-wave density profile, but not the temperature profile, and hence are not satisfactory. A tentative computational model for nitrogen is explored which yields considerably more realistic results than the Navier-Stokes equations. This model involves a nonlinear stress-strain tensor, nonlinear heat flux vector, and nonequilibrium rotational energy.
    Keywords: AERODYNAMICS
    Type: Sensing, Discrimination, and Signal Processing and Superconducting Materials and Instrumentation; Jan 12, 1988 - Jan 14, 1988; Los Angeles, CA; United States
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  • 8
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    Development and refinement of test bed simulations (1989)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Lewis Research Center of NASA, with support from Rocketdyne, was engaged in non-real time computer simulation effort for the Space Station Freedom Electric Power System (EPS) EASY5, a simulation package, is used as the primary tool for this activity. Early in the design of the EPS, two test beds were set up at Lewis. The Integrated Test Bed (ITB), that combines and upgrades these test beds, is in the planning stage. The test beds are designed to functionally represent many of the components of the EPS and their interconnections. The simulation effort is primarily directed towards these test beds. Model verification is performed using test bed data.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-102335 , E-5043 , NAS 1.15:102335 , Intersociety Energy Conversion Engineering Conference; Aug 06, 1989 - Aug 11, 1989; Washington, DC; United States
    Format: application/pdf
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  • 9
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    Feasibility of self-structured current accessed bubble devices in spacecraft recording systems (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The self-structured, current aperture approach to magnetic bubble memory is described. Key results include: (1) demonstration that self-structured bubbles (a lattice of strongly interacting bubbles) will slip by one another in a storage loop at spacings of 2.5 bubble diameters, (2) the ability of self-structured bubbles to move past international fabrication defects (missing apertures) in the propagation conductors (defeat tolerance), and (3) moving bubbles at mobility limited speeds. Milled barriers in the epitaxial garnet are discussed for containment of the bubble lattice. Experimental work on input/output tracks, storage loops, gates, generators, and magneto-resistive detectors for a prototype device are discussed. Potential final device architectures are described with modeling of power consumption, data rates, and access times. Appendices compare the self-structured bubble memory from the device and system perspectives with other non-volatile memory technologies.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: NASA-CR-172554 , NAS 1.26:172554
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  • 10
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    Laser Doppler Velocimeter System (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Seeded flows measured optically. Laser Doppler velocimeter integrated with wind-tunnel pressure vessel with mounting system minimizing effects of vibrations and of pressure and thermal strains.
    Keywords: PHYSICAL SCIENCES
    Type: ARC-11679 , NASA Tech Briefs (ISSN 0145-319X); 12; 2; P. 47
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