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  • Other Sources  (37,314)
  • GEOPHYSICS  (21,936)
  • FLUID MECHANICS AND HEAT TRANSFER  (8,825)
  • ENERGY PRODUCTION AND CONVERSION  (6,553)
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  • 1
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    Results and current status of the NPARC alliance validation effort (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NPARC Alliance is a partnership between the NASA Lewis Research Center (LeRC) and the USAF Arnold Engineering Development Center (AEDC) dedicated to the establishment of a national CFD capability, centered on the NPARC Navier-Stokes computer program. The three main tasks of the Alliance are user support, code development, and validation. The present paper is a status report on the validation effort. It describes the validation approach being taken by the Alliance. Representative results are presented for laminar and turbulent flat plate boundary layers, a supersonic axisymmetric jet, and a glancing shock/turbulent boundary layer interaction. Cases scheduled to be run in the future are also listed. The archive of validation cases is described, including information on how to access it via the Internet.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-107134 , NAS 1.15:107134 , E-10064 , AIAA PAPER 96-0387 , NIPS-96-08124 , Aerospace Sciences Meeting and Exhibit; Jan 15, 1996 - Jan 18, 1996; Reno, NV; United States
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  • 2
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    Evolution of the Pinatubo volcanic cloud over Hampton, Virginia (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The eruption of Mt. Pinatubo in June 1991 produced the largest enhancement of stratospheric aerosol loading ever observed by lidar over Hampton, Virginia. Low altitude layers (less than 20 km) were the first to arrive over Hampton in early August, the result of transport associated with a tropospheric anticyclonic cell over North America. The maximum peak scattering ratio, 34 at 22.4 km, and the maximum stratospheric integrated backscatter of 0.0053 sr(exp -1), both at 694 nm, observed since the eruption were measured on February 20, 1992. After decreasing during the spring and summer of 1992, the aerosol burden increased significantly during the winter of 1992-93, evidence of a poleward winter transport from the equatorial reservoir. Over the period from February 1992 to February 1994, the stratospheric aerosol loading decreased with an average 1/e decay time of 10.1 months. The vertical distribution, intensity, and transport of Pinatubo aerosols over this site are described and compared with similar measurements after El Chichon.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 9; p. 1101-1104
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  • 3
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    Nonsphericity of dust-like tropospheric aerosols: Implications for aerosol remote sensing and climate modeling (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: T-matrix computations of light scattering by polydispersions of randomly oriented nonspherical aerosols and Mie computations for equivalent spheres are compared. Findings show that even moderate nonsphericity results in suubstantial errors in the retrieved aerosol optical thickness if satellite reflectance measurements are analyzed using Mie theory. On the other hand, the use of Mie theory for nonspherical aerosols produces negligible errors in the computation of albedo and flux related quantities, provided that the aerosol size distribution and optical thickness are known beforehand. The first result can be explained by large nonspherical-spherical differences in scattering phase function, while the second result follows from small nonspherical-spherical differences in single-scattering albedo and asymmetry parameter. No cancellation of errors occurs if one consistently uses Mie theory in the retrieval algorithm and then in computing the albedo for the retrieved aerosol optical thickness.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 9; p. 1077-1080
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  • 4
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    Atmospheric gradients from very long baseline interferometry observations (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Azimuthal asymmetries in the atmospheric refractive index can lead to errors in estimated vertical and horizontal station coordinates. Daily average gradient effects can be as large as 50 mm of delay at a 7 deg elevation. To model gradients, the constrained estimation of gradient paramters was added to the standard VLBI solution procedure. Here the analysis of two sets of data is summarized: the set of all geodetic VLBI experiments from 1990-1993 and a series of 12 state-of-the-art R&D experiments run on consecutive days in January 1994. In both cases, when the gradient parameters are estimated, the overall fit of the geodetic solution is improved at greater than the 99% confidence level. Repeatabilities of baseline lengths ranging up to 11,000 km are improved by 1 to 8 mm in a root-sum-square sense. This varies from about 20% to 40% of the total baseline length scatter without gradient modeling for the 1990-1993 series and 40% to 50% for the January series. Gradients estimated independently for each day as a piecewise linear function are mostly continuous from day to day within their formal uncertainties.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 9; p. 1041-1044
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  • 5
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    Centrifugal trapping in the magnetotail (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Particles leving the neutral sheet in the distant magnetotail at times display adiabatic trajectory sequences characterized by an inflection toward the equator and subsequent mirroring in its vicinity. We demonstrate that this low-latitude mirroring results primarily from a centrifugal deceleration due to the fast direction-changing E x B drift. This effect which we refer to as 'centrifugal trapping' appears both in guiding centre and full particle treatments. It thus does not directly relate to nonadiabatic motion. However, pitch angle scattering due to nonadiabatic neutral sheet interaction does play a role in reducing the parallel speed of the particles. We show that centrifugal trapping is an important mechanism for the confinement of the slowest (typically below the equatorial E x B drift speed) plasma sheet populations to the midplane vicinity.
    Keywords: GEOPHYSICS
    Type: Annales Geophysicae (ISSN 0992-7689); 13; 3; p. 242-246
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  • 6
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    Marangoni instability in a liquid sheet (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We study the onset of a pure Marangoni convection in a liquid layer with two deformable interfaces in the no-gravity environment. Both oscillatory and stationary instabilities are considered for a wide range of parameters. It is shown that only stationary instability is possible when surface tension at the colder interface is lower than that at the hotter one. Oscillatory instability tends to disappear and to be replaced by the stationary instability with increase of the Prandtl number and decrease of surface tension at the colder interface.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Advances in Space Research (ISSN 0273-1177); 16; 7; p. (7)83-(7)86
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  • 7
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    Radiative transfer in a semiinfinite medium with a specularly reflecting boundary (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A consistent solution of the radiative transfer equation characterizing photon transport in a semi-infinite medium of refractive index greater than or equal to one is obtained following the method of Sobolev. Fresnel specular reflection, Snell's law and isotropic scattering are assumed. An algorithm is developed and its accuracy is demonstrated. A numerical Laplace transform inversion leads to an efficient evaluation for the interior flux and source function distributions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Quantitative Spectroscopy & Radiative Transfer (ISSN 0022-4073); 53; 3; p. 257-267
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  • 8
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    Three-dimensional magnetic reconnection and the magnetic topology of coronal mass ejection events (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Measurements of superthermal electron fluxes in the solar wind indicate that field lines within coronal mass ejections, CMEs, near and beyond 1 AU are normally connected to the Sun at both ends. However, on occasion some field lines embedded deep within CMEs appear to be connected to the Sun at only one end. Here we propose an explanation for how such field lines arise in terms of 3-dimensional reconnection close to the Sun. Such reconnection also provides a natural explanation for the flux rope topology characteristic of many CMEs as well as the coronal loops formed during long-duration, solar X-ray events. Our consideration of the field topologies resulting from 3-dimensional reconnection indicates that field lines within and near CMEs may on occasion be connected to the outer heliosphere at both ends.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 8; p. 869-872
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  • 9
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    The efficiency of 'viscous interaction' between the solar wind and the magnetosphere during intense northward IMF events (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We examined 11 cases when the interplanetary magnetic field (IMF) was intensely northward (greater than 10 nT) for long durations of time (greater than 3 hours), to quantitatively determine an uppler limit on the efficiency of solar wind energy injection into the magnetosphere. We have specifically selected these large B(sub N) events to minimize the effects of magnetic reconnection. Many of these cases occurred during intervals of high-speed streams associated with coronal mass ejections when viscous interaction effects might be at a maximum. It is found that the typical efficiency of solar wind energy injection into the magnetosphere is 1.0 x 10(exp -3) to 4.0 x 10(exp -3), 100 to 30 times less efficient than during periods of intense southward IMFs. Other energy sinks not included in these numbers are discussed. Estimates of their magnitudes are provided.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 6; p. 663-666
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  • 10
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    The Earth's magnetosphere is 165 R(sub E) long: Self-consistent currents, convection, magnetospheric structure, and processes for northward interplanetary magnetic field (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The subject of this paper is a self-consistent, magnetohydrodynamic numerical realization for the Earth's magnetosphere which is in a quasi-steady dynamic equilibrium for a due northward interplanetary magnetic field (IMF). Although a few hours of steady northward IMF are required for this asymptotic state to be set up, it should still be of considerable theoretical interest because it constitutes a 'ground state' for the solar wind-magnetosphere interaction. Moreover, particular features of this ground state magnetosphere should be observable even under less extreme solar wind conditions. Certain characteristics of this magnetosphere, namely, NBZ Birkeland currents, four-cell ionospheric convection, a relatively weak cross-polar potential, and a prominent flow boundary layer, are widely expected. Other characteristics, such as no open tail lobes, no Earth-connected magnetic flux beyond 155 R(sub E) downstream, magnetic merging in a closed topology at the cusps, and a 'tadpole' shaped magnetospheric boundary, might not be expected. In this paper, we will present the evidence for this unusual but interesting magnetospheric equilibrium. We will also discuss our present understanding of this singular state.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A3; p. 3623-3635
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  • 11
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    Localized tearing modes in the magnetotail driven by curvature effects (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The stability of collisionless tearing modes is examined in the presence of curvature drift resonances and the trapped particle effects. A kinetic description for both electrons and ions is employed to investigate the stability of a two-dimensional equilibrium model. The main features of the study are to treat the ion dynamics properly by incorporating effects associated with particle trajectories in the tail fields and to include the linear coupling of trapped particle modes. Generalized dispersion relations are derived in several parameter regimes by considering two important sublayers of the reconnecting region. For a typical choice of parameters appropriate to the current sheet region, we demonstrate that localized tearing modes driven by ion curvature drift resonance effects are excited in the current sheet region with growth time of the order of a few seconds. Also, we examine nonlocal characteristics of tearing modes driven by curvature effects and show that modes growing in a fraction of a second arise when mode widths are larger than the current sheet width. Further, we show that trapped particle effects, in an interesting frequency regime, significantly enhance the growth rate of the tearing mode. The relevance of this theory for substorm onset phase and other features of the substorms is briefly discussed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A3; p. 3563-3572
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  • 12
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    PULSAUR 2: Rocket and groundbased measurements in a pulsating aurora (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The second pulsating aurora rocket (PULSAUR 2) rocket was launched into a pulsating aurora on 9 February 1994 and carried a broad range of instruments in order to perform a study of this type of aurora. The rocket measurements were complemented with a set of ground-based measurements. The particle measurements performed in the rocket are related to the ground-based optical measurements performed along the rocket trajectory. It is found that the high energy electrons are largely in phase with the measured luminosity. The EISCAT measurements carried out during the flight are reviewed. The PULSAUR 2 campaign is described. Results concerning the auroral conditions and the particle measurements are presented.
    Keywords: GEOPHYSICS
    Type: ESA, Proceedings of 12th ESA Symposium on European Rocket and Balloon Programmes and Related Research; p 233-237
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  • 13
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    High-speed correction factor to the O(+)-O resonance charge exchange collision frequency (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The high-speed correction factor to the O(+)-O collision frequency, resulting from drift velocities between ions and neutrals, is calculated by solving the integral expression in this factor both numerically and analytically. Although the analytic solution is valid for either small or large drift velocities between ions and neutrals, for temperatures of interest and all drift velocities considered, agreement is found between analytic and detailed numerical integration results within less than 1% error. Let T(sub r) designate the average of the ion and neutral temperatures in K, and u = nu(sub d)/alpha, where nu(sub d) is the relative drift velocity in cm/s, and alpha = 4.56 x 10(exp 3) square root of T(sub r) cm/s is the thermal velocity of the O(+)-O system. Then, as u ranges from 0 to 2, the correction factor multiplying the collision frequency increases monotonically from 1 to about 1.5. An interesting result emerging from this calculation is that the correction factor for temperatures of aeronomical interest is to a good approximation independent of the temperature, depending only on the scaled velocity u.
    Keywords: GEOPHYSICS
    Type: Annales Geophysicae (ISSN 0992-7689); 13; 3; p. 253-255
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  • 14
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    An efficient algorithm for choosing scattering directions in Monte Carlo work with arbitrary phase functions (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: This paper describes an efficient Monte Carlo algorithm for choosing a new direction of a photon after a scattering interaction. The algorithm chooses a scattering angle by linear interpolation in a table of the inverse cumulative scattering probability. A Legendre expansion of the phase function makes it easy to apply Clenshaw's algorithm to build the interpolation table. The points in the table are close enough together that linear interpolation is accurate. With a table of 100,000 entries, we can keep the absolute and relative errors in matching the probability distribution below 10(exp -5).
    Keywords: GEOPHYSICS
    Type: Journal of Quantitative Spectroscopy & Radiative Transfer (ISSN 0022-4073); 53; 1; p. 23-38
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  • 15
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    On the uniqueness of linear moving-average filters for the solar wind-auroral geomagnetic activity coupling (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The relation between the solar wind input to the magetosphere, VB(sub South), and the auroral geomagnetic index AL is modeled with two linear moving-average filtering methods: linear prediction filters and a driven harmonic oscillator in the form of an electric circuit. Although the response of the three-parameter oscillator is simpler than the filter's, the methods yield similar linear timescales and values of the prediction-observation correlation and the prediction Chi(exp 2). Further the filter responses obtained by the two methods are similar in their long-term features. In these aspects the circuit model is equivalent to linear prediction filtering. This poses the question of uniqueness and proper interpretation of detailed features of the filters such as response peaks. Finally, the variation of timescales and filter responses with the AL activity level is discussed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A4; p. 5637-5641
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  • 16
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    Modeling the Earth's magnetospheric magnetic field confined within a realistic magnetopause (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Empirical data-based models of the magnetosphereic magnetic field have been widely used during recent years. However, the existing models (Tsyganenko, 1987, 1989a) have three serious deficiencies: (1) an unstable de facto magnetopause, (2) a crude parametrization by the K(sub p) index, and (3) inaccuracies in the equatorial magnetotail B(sub z) values. This paper describes a new approach to the problem; the essential new features are (1) a realistic shape and size of the magnetopause, based on fits to a large number of observed crossing (allowing a parametrization by the solar wind pressure), (2) fully controlled shielding of the magnetic field produced by all magnetospheric current systems, (3) new flexible representations for the tail and ring currents, and (4) a new directional criterion for fitting the model field to spacecraft data, providing improved accuracy for field line mapping. Results are presented from initial efforts to create models assembled from these modules and calibrated against spacecraft data sets.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A4; p. 5599-5612
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  • 17
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    Some velocity field results from the thermocapillary flow experiment aboard USML-1 spacelab (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Results are reported of the Surface Tension Driven Convection Experiment (STDCE) aboard USML-1 Spacelab. Steady and transient thermocapillary flows were investigated in a 10 cm dia. circular container filled with 10 Cs silicone oil. The velocity and temperature fields were studied in detail under various conditions. It is shown in this paper how the Marangoni number affects the velocity field. A numerical analysis of the flows was also conducted and its results were compared to the experimental data. Good agreement is shown.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Advances in Space Research (ISSN 0273-1177); 16; 7; p. (7)79-(7)82
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  • 18
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    The middle atmospheric response to short and long term solar UV variations: analysis of observations and 2D model results (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We have investigated the middle atmospheric response to the 27-day and 11-yr solar UV flux variations at low to middle latitudes using a two-dimensional photochemical model. The model reproduced most features of the observed 27-day sensitivity and phase lag of the profile ozone response in the upper stratosphere and lower mesosphere, with a maximum sensitivity of +0.51% per 1% change in 205 nm flux. The model also reproduced the observed transition to a negative phase lag above 2 mb, reflecting the increasing importance with height of the solar modulated HO(x) chemistry on the ozone response above 45 km. The model revealed the general anti-correlation of ozone and solar UV at 65-75 km, and simulated strong UV responses of water vapor and HO(x) species in the mesosphere. Consistent with previous 1D model studies, the observed upper mesospheric positive ozone response averaged over +/- 40 was simulated only when the model water vapor concentrations above 75 km were significantly reduced relative to current observations. In agreement with observations, the model computed a low to middle latitude total ozone phase lag of +3 days and a sensitivity of +0.077% per 1% change in 205 nm flux for the 27-day solar variation, and a total ozone sensitivity of +0.27% for the 11-yr solar cycle. This factor of 3 sensitivity difference is indicative of the photochemical time constant for ozone in the lower stratosphere which is comparable to the 27-day solar rotation period but is much shorter than the 11-yr solar cycle.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169); 57; 4; p. 333-365
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  • 19
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    Accuracy of satellite altimeter elevations over the Greenland ice sheet (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The accuracy of Geosat satellite altimetry over the Greenland ice sheet is evaluated by comparing the measured heights to radar elevations from the airborne Greenland Aerogeophysics Project. At the center of the ice sheet where the ice surface is nearly level, surface comparisons show a fit at the 1 to 3 m level as expected, but even at moderately sloping ice regions (0.3 deg-0.6 deg), satellite altimetry mean errors in the range of 10 to 35 m are observed. These errors are found for slope-corrected and waveform-retracked data, so most previous accuracy estimates of current satellite altimetry ice sheet elevations in regions of slopping or undulating ice appear to be too optimistic.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; C2; p. 2687-2696
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  • 20
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    Satellite observations of zonal electric fields near sunrise in the equatorial ionosphere (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We report here on a number of examples of anomalous enhancements of eastward electric fields near sunrise in the equatorial ionospheric F-region. These examples were selected from the data base of the equatorial satellite, San Marco D (1988), which measured ionospheric electric fields during a period of solar minimum. The eastward electric fields reported correspond to vertical plasma drifts. The examples studied here are similar in signature and polarity to the pre-reversal electric field enhancements seen near sunset from ground-based radar systems. The morphology of these sunrise events, which are observed on about 14% of the morning-side satellite passes, are studied as a function of local zonal velocity, magnetic activity, geographic longitude and altitude. The nine events studied occur at locations where the zonal plasma flow is generally measured to be eastward, but reducing as a function of local time and at satellite longitudes where the magnetic declination has the opposite polarity as the declination of the sunrise terminator.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169); 57; 1; p. 19-24
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  • 21
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    A description of the solar wind-magnetosphere coupling based on nonlinear filters (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A nonlinear filtering method is introduced for the study of the solar wind -- magnetosphere coupling and related to earlier linear techniques. The filters are derived from the magnetospheric state, a representation of the magnetospheric conditions in terms of a few global variables, here the auroral electrojet indices. The filters also couple to the input, a representation of the solar wind variables, here the rectified electric field. Filter-based iterative prediction of the indices has been obtained for up to 20 hours. The prediction is stable with respect to perturbations in the initial magnetospheric state; these decrease exponentially at the rate of 30/min. The performance of the method is examined for a wide range of parameters and is superior to that of other linear and nonlinear techniques. In the magnetospheric state representation the coupling is modeled as a small number of nonlinear equations under a time-dependent input.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A3; p. 3495-3512
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  • 22
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    Topological structure of the magnetotail as a function of interplanetary magnetic field direction (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Magnetic reconnection between the interplanetary magnetic field (IMF) and the geomagnetic field is thought to play a major role in the transfer of solar wind momentum and energy to the magnetosphere. As the angle between the IMF and the geomagnetic field is changed at the bow of the magnetosphere, the topological record of the location of the reconnection region should be recorded in the magnetosheath and on the magnetopause along the flanks of the tail, because the super fast flow freezes strong magnetic gradients formed in the bow reconnection regions into the plasma downstream. In this report, we present results from a three-dimensional, magnetohydrodynamic (MHD), global numerical simulation code for the location of the separatrix between unconnected IMF magnetosheath field lines and reconnected field lines which penetrate the magnetopause and connect to the polar ionosphere. The angle between the IMF direction and the line where the separatrix crosses the magnetopause is shown to be a sensitive function of the IMF clock angle. We also explain how this behavior can be used to derive an approximate relation for the dependence of the cross-polar voltage on the IMF clock angle. We conclude with a note of caution concerning the importance of physical boundary conditions in magnetoplasma simulations.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A3; p. 3613-3621
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  • 23
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    Spatial symmetry breaking in rapidly rotating convective spherical shells (1995)
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    Publication Date: 2011-08-24
    Description: Many problems in geophysical and astrophysical convection systems are characterized by fast rotation and spherical shell geometry. The combined effects of Coriolis forces and spherical shell geometry produce a unique spatial symmetry for the convection pattern in a rapidly rotating spherical shell. In this paper, we first discuss the general spatial symmetries for rotating spherical shell convection. A special model, a spherical shell heated from below, is then used to illustrate how and when the spatial symmetries are broken. Symmetry breaking occurs via a sequence of spatial transitions from the primary conducting state to the complex multiple-layered columnar structure. It is argued that, because of the dominant effects of rotation, the sequence of spatial transitions identified from this particular model is likely to be generally valid. Applications of the spatial symmetry breaking to planetary convection problems are also discussed.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 10; p. 1265-1268
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  • 24
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    Preliminary results from the Sprites94 aircraft campaign: 2. Blue jets (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Initial observations of a newly documented type of optical emission above thunderstorms are reported. 'Blue jets', or narrowly collimated beams of blue light that appear to propagate upwards from the tops of thunderstorms, were recorded on B/W and color video cameras for the first time during the Sprites94 aircraft campaign, June-July, 1994. The jets appear to propagate upward at speeds of about 100 km/s and reach terminal altitudes of 40-50 m. Fifty six examples were recorded during a 22 minute interval during a storm over Arkansas. We examine some possible mechanisms, but have no satisfactory theory of this phenomenon.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 10; p. 1209-1212
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  • 25
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    The contribution of flux transfer events to convection (1995)
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    Publication Date: 2011-08-24
    Description: It is shown from flux transfer event (FTE) occurrence statistics, observed as a function of MLT by the ISEE satellites, that recent 2-dimensional analytic theories of the effects of pulsed Petschek reconnection predict FTEs to contribute between 50 and 200 kV to the total reconnection voltage when the magnetosheath field points southward. The upper limit (200 kV) allows the possibility that FTEs provide all the antisunward transport of open field lines into the tail lobe. This range is compared with the voltages associated with series of FTEs signatures, as inferred from ground-based observations, which are in the range 10-60 kV. We conclude that the contribution could sometimes be made by a series of single, large events; however, the voltage is often likely to be contributed by several FTEs at different MLT.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 10; p. 1185-1188
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    Observations of downward moving O(+) in the polar topside ionosphere (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: New investigations of the core ion motion within high-latitude topside ionosphere and near-Earth magnetosphere, using data from the Dynamics Explorer (DE) retarding ion mass spectrometer (RIMS), reveal the existence of significant regions of downward moving O(+). The occurences of downgoing versus upgoing O(+) are not clearly separable in terms of either polar zenith angle or Kp but are well distinquished by the direction of the z component of the interplanetary magnetic field (IMF). On the average, down flow dominates when IMFB2 less than O, while upflow dominates for IMFB2 greater than 0. Combining cross-field convection velocities derived from an empirical convection electric field model with the observed parallel velocities yields a two dimensional ion velocity field. This velocity field is consistent with a senario which has O(+) of cusp/cleft and auroral zone origin concvecting into the polar cap and, because of the dominance of gravitational energy over the upward kinetic energy, falling back into the inonsphere. This provides additional confirmation of the results of studies of the cleft ion fountain. Estimates of the flux of O(+) in the upflowing and downflowing regions for Lambda greater than or equal to 60 deg give a total upflow of approximately 6 X 10(exp 25) ions/sec for IMFB2 greater than 0 and total upflow and downflow of approximately 4 X 10 (exp 25) ions/sec and 1 x 10(exp 25) ions/sec, respectively, for IMFB less than 0. In all cases the magnitude of the dayside outflow is consistent with previous work on upwelling ions. While the magnitudes vary for high and low Kp the ratios of upward to downward flow are roughly the same at approximately 1.7. The downflowing O(+) shows a correlation with the magnitude of the outflow of light ions in the same region but the cause and effect of this relationship is not distinquishable. hable.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A4; p. 5795-5800
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    Time-domain approach for the transient responses in stratified viscoelastic Earth models (1995)
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    Publication Date: 2011-08-24
    Description: We have developed the numerical algorithm for the computation of transient viscoelastic responses in the time domain for a radially stratified Earth model. Stratifications in both the elastic parameters and the viscosity profile have been considered. The particular viscosity profile employed has a viscosity maximum with a constrast of O(100) in the mid lower mantle. The distribution of relaxation times reveals the presence of a continuous spectrum situated between O(100) and O(exp 4) years. The principal mode is embedded within this continuous spectrum. From this initial-value approach we have found that for the low degree harmonics the non-modal contributions are comparable to the modal contributions. For this viscosity model the differences between the time-domain and normal-mode results are found to decrease strongly with increasing angular order. These calculations also show that a time-dependent effective relaxation time can be defined, which can be bounded by the relaxation times of the principal modes.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 10; p. 1285-1288
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  • 28
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    Plasma gradient effets on doubel-probe measurements in the magnetosphere (1995)
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    Publication Date: 2011-08-24
    Description: The effects on double-probe electric field measurements induced by electron density and temperature gradients are investigated. We show that on some occasions such gradients may lead to marked spurious electric fields if the probes are assumed to lie at the same probe potential with repect to the plasma. The use of a proper bias current will decrease the magnitude of such an error. When the probes are near the plasma potential, the magnitude of these error signals, delta Epsilon, can vary as delta Epsilon approx. T(sub e)(Delta n(sub e)/n(sub e)) + 0.5 Delta T(sub e), where T(sub e) is the electron temperature, Delta n(sub e)/ n(sub e) the relative electron density variation between the two sensors, and Delta T(sub e) the electron temperature difference between the two sensors. This not only implies that the error signals will increase linearly with the density variations but also that such signatures grow with Delta T(sub e) i.e., such effects are 10 times larger in a 10-eV plasma than in a 1-eV plasma. This type of error is independent of the probe separation distance provided the gradient scale length is much larger than the distance. The largest errors occur when the probes are near to the plasma potential. During the crossing of a small structure (e.g, a double layer) the error signal appears as a bipolar signature. Our analysis shows that errors in double-probe measurements caused by plasma gradients are not significant at large scale (much greater than 1 km) plasma boundaries, and may only be important in cases where small-scale (less than 1 km), internal gradient structures exist. Bias currents tailored for each plasma parameter regime (i.e., variable bias current) would improve the double-probe response to gradient effects considerably.
    Keywords: GEOPHYSICS
    Type: Annales Geophysicae (ISSN 0992-7689); 13; 2; p. 130-146
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  • 29
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    Evolution of the Pinatubo volcanic aerosol column above Pasadena, California observed with a mid-infrared backscatter lidar (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The evolution of the volcanic debris plume originating from the June 1991 eruption of Mt. Pinatubo has been monitored since its genesis using a ground-based backscatter lidar facility sited at the Jet Propulsion Laboratory (JPL). Both absolute and relative pre- and post-Pinatubo backscatter observations are in accord with Mie scattering projections based on measured aerosol particle size distributions reported in the literature. The post-Pinatubo column-integrated backscatter coefficient peaked approximately 400 days after the eruption, and the observed upper boundary of the aerosol column subsided at a rate of approximately 200 m/mon.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 22; 7; p. 807-810
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    Uplift of the Kenai Peninsula, Alaska, since the 1964 Prince William Sound earthquake (1995)
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    Publication Date: 2011-08-24
    Description: Using Global Positioning System (GPS) receivers, we reoccupied several leveling benchmarks on the Kenai Peninsula of Alaska which had been surveyed by conventional leveling immediately following the March 27, 1964, Prince William Sound earthquake (M(sub w) = 9.3). By combining the two sets of measurements with a new, high-resolution model of the geoid in the region, we were able to determine the cumulative 1993-1964 postseismic vertical displacement. We find uplift at all of our benchmarks, relative to Seward, Alaska, a point that is stable according to tide gauge data. The maximum uplift of about 1 m occurs near the middle of the peninsula. The region of maximum uplift appears to be shifted northwest relative to the point of maximum coseismic subsidence. If we use tide gauge data at Nikishka and Seward to constrain the vertical motion, then the observed uplift has a trenchward tilt (down to the southeast) as well as an arching component. To explain the observations, we use creep-at-depth models. Most acceptable models require a fault slip of about 2.75 m, although this result is not unique. If the slip has been continuous since the 1964 earthquake, then the average slip rate is nearly 100 mm/yr, twice the plate convergence rate. Comparing the net uplift achieved in 29 years with that observed over 11 years in an adjacent region southeast of Anchorage, Alaska, we conclude that the rate of uplift is decreasing. A further decrease in the uplift rate is expected as the 29-year averaged displacement rate is about twice the plate convergence rate and therefore cannot be sustained over the entire earthquake cycle.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; B2; p. 2031-2038
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    Electron structures in the cusp/cleft region observed by DE 2 satellite (1995)
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    Publication Date: 2011-08-24
    Description: Narrow enhancements of electron precipitation, with energy and flux well above typical values, have been observed with Dynamics Explorer 2 (DE 2) in the cusp/cleft region. The electron flux in the energy range 0.2-1 keV was 2 orders of magnitude higher in these structures than in the magnetosheath and were seen in approximaetly 80% of DE 2 cusp crossings at ionospheric altitudes. Typically, there was more than one electron structure in each cusp crossing. The position of these structures showed a systematic variation: for poleward ion dispersion (energy decreases with increasing latitude), electron structures were seen more often on the equatorial boundary of the cusp, while for equatorward ion dispersion (energy decreases with decreasing latitude), electron structures were more often seen on the poleward boundary. This suggests that the electron structures are associated with newly reconnected field lines. The electron spectra suggest that field-aligned acceleration processes could produce the electron structures, first near the boundary of the cusp/cleft during the reconnection of field lines and then in the cusp/cleft during the motion of reconnected flux tubes through the polar ionosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A2; p. 1597-1610
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    Inflation of Long Valley Caldera from 1 year of continuous GPS observations (1995)
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    Publication Date: 2011-08-24
    Description: A permanent Global Positioning System (GPS) receiver at Casa Diablo Hot Springs, Long Valley Caldera, California was installed in January, 1993, and has operated almost continuously since then. The data have been transmitted daily to the Jet Propulsion Laboratory (JPL) for routine analysis with data from the Fiducial Laboratories for an International Natural sciences Network (FLINN) by the JPL FLINN analysis center. Results from these analyses have been used to interpret the on going deformation at Long Valley, with data excluded from periods when the antenna was covered under 2.5 meters of snow and from some periods when Anti Spoofing was enforced on the GPS signal. The remaining time series suggests that uplift of the resurgent dome of Long Valley Caldera during 1993 has been 2.5 +/- 1.1 cm/yr and horizontal motion has been 3.0 +/- 0.7 cm/yr at S53W in a no-net-rotation global reference frame, or 1.5 +/- 0.7 cm/yr at S14W relative to the Sierra Nevada block. These rates are consistent with uplift predicted from frequent horizontal strain measurements. Spectral analysis of the observations suggests that tidal forcing of the magma chamber is not a source of the variability in the 3 dimensional station location. These results suggest that remotely operated, continuously recording GPS receivers could prove to be a reliable tool for volcanic monitoring throughout the world.
    Keywords: GEOPHYSICS
    Type: Geopysical Research Letters (ISSN 0094-8276); 22; 3; p. 195-198
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    Comparison between SAGE II and ISCCP high-level clouds. 2: Locating clouds tops (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A comparison is made of the vertical distribution of high-level cloud tops derived from the Stratospheric Aerosol and Gas Experiment II (SAGE II) occultation measurements and from the International Satellite Cloud Climatology Project (ISCCP) for all Julys and Januarys in 1985 to 1990. The results suggest that ISCCP overestimates the pressure of high-level clouds by up to 50-150 mbar, particularly at low latitudes. This is caused by the frequent presence of clouds with diffuse tops (greater than 50% time when cloudy events are observed). The averaged vertical extent of the diffuse top is about 1.5 km. At midlatitudes where the SAGE II and ISCCP cloud top pressure agree best, clouds with distinct tops reach a maximum relative proportion of the total level cloud amount (about 30-40%), and diffuse-topped clouds are reduced to their minimum (30-40%). The ISCCP-defined cloud top pressure should be regarded not as the material physical height of the clouds but as the level which emits the same infrared radiance as observed. SAGE II and ISCCP cloud top pressures agree for clouds with distinct tops. There is also an indication that the cloud top pressures of optically thin clouds not overlying thicker clouds are poorly estimated by ISCCP at middle latitudes. The average vertical extent of these thin clouds is about 2.5 km.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; D1; p. 1137-1147
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    Comparison between SAGE II and ISCCP high-level clouds. 1: Global and zonal mean cloud amounts (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Global high-level clouds identified in Stratospheric Aerosol and Gas Experiment II (SAGE II) occultation measurements for January and July in the period 1985 to 1990 are compared with near-nadir-looking observations from the International Satellite Cloud Climatology Project (ISCCP). Global and zonal mean high-level cloud amounts from the two data sets agree very well, if clouds with layer extinction coefficients of less than 0.008/km at 1.02 micrometers wavelength are removed from the SAGE II results and all detected clouds are interpreted to have an average horizontal size of about 75 km along the 200 km transimission path length of the SAGE II observations. The SAGE II results are much more sensitive to variations of assumed cloud size than to variations of detection threshold. The geographical distribution of cloud fractions shows good agreement, but systematic regional differences also indicate that the average cloud size varies somewhat among different climate regimes. The more sensitive SAGE II results show that about one third of all high-level clouds are missed by ISCCP but that these clouds have very low optical thicknesses (less than 0.1 at 0.6 micrometers wavelength). SAGE II sampling error in monthly zonal cloud fraction is shown to produce no bias, to be less than the intraseasonal natural variability, but to be comparable with the natural variability at longer time scales.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; D1; p. 1121-1135
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    Relativistic electron fluxes in May 1992 and their effect on the middle atmosphere (1995)
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    Publication Date: 2011-08-24
    Description: Enhancements in the fluxes of relativistic electrons trapped within the Earth's magnetosphere have been measured by the high-energy particle spectrometer, part of the particle environment monitor on the upper atmosphere research satellite (UARS). The largest increase in the electron fluxes with energies greater than 1 MeV observed on UARS from October 1991 through July 1994 was in early May 1992. The fluxes of trapped electrons in the drift loss cone and locally precipitating electrons showed differing buildup and decay rates as a function of invariant latitude. Increases of more than 2 orders of magnitude were observed in drift loss cone fluxes at magnetic latitudes of 40 deg-66 deg and in precipitating fluxes from 48 deg to 66 deg. The energy flux contained in the most intense local precipitation observed was approximately 0.1 erg/sq cm/s, entering the atmosphere and creating up to 1000 ion pairs/cu cm/s at 55-km altitude. The daily averaged energy flux from directly precipitating electrons with energies greater than 1 MeV deposited greater than 10(exp 20) erg/d worldwide into the atmosphere for the period May 12-21, 1992, producing greater than 10(exp 31) odd nitrogen molecules below 60-km altitude.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; D1; p. 1027-1033
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    Low temperature Zn diffusion for GaSb solar cell structures fabrication (1995)
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    Publication Date: 2011-08-24
    Description: Low temperature Zn diffusion in GaSb, where the minimum temperature was 450 C, was studied. The pseudo-closed box (PCB) method was used for Zn diffusion into GaAs, AlGaAs, InP, InGaAs and InGaAsP. The PCB method avoids the inconvenience of sealed ampoules and proved to be simple and reproducible. The special design of the boat for Zn diffusion ensured the uniformality of Zn vapor pressure across the wafer surface, and thus the uniformity of the p-GaSb layer depth. The p-GaSb layers were studied using Raman scattering spectroscopy and the x-ray rocking curve method. As for the postdiffusion processing, an anodic oxidation was used for a precise thinning of the diffused GaSb layers. The results show the applicability of the PCB method for the large-scale production of the GaSb structures for solar cells.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 641-644
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    Indium phosphide space solar cell research: Where we are and where we are going (1995)
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    Publication Date: 2011-08-24
    Description: Indium phosphide is considered to be a strong contender for many photovoltaic space applications because of its radiation resistance and its potential for high efficiency. An overview of recent progress is presented, and possible future research directions for indium phosphide space solar cells are discussed. The topics considered include radiation damage studies and space flight experiments.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 469-470
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    High efficiency solar cells for laser power beaming applications (1995)
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    Publication Date: 2011-08-24
    Description: Understanding solar cell response to pulsed laser outputs is important for the evaluation of power beaming applications. The time response of high efficiency GaAs and silicon solar cells to a 25 nS monochromatic pulse input is described. The PC-1D computer code is used to analyze the cell current during and after the pulse for various conditions.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 483-485
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    Mechanically stacked concentrator tandem solar cells (1995)
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    Publication Date: 2011-08-24
    Description: Four-terminal mechanically stacked solar cells were developed for advanced space arrays with line-focus reflective concentrators. The top cells are based on AlGaAs/GaAs multilayer heterostructures prepared by low temperature liquid phase epitaxy. The bottom cells are based on heteroepitaxial InP/InGaAs liquid phase epitaxy or on homo-junction GaSb, Zn-diffused structures. The sum of the highest reached efficiencies of the top and bottom cells is 29.4 percent. The best four-terminal tandems have an efficiency of 27 to 28 percent. Solar cells were irradiated with 1 MeV electrons and their performances were determined as a function of fluence up to 10(exp 16) cm(exp-2). It was shown that the radiation resistance of developed tandem cells is similar to the most radiative stable AlGaAs/GaAs cells with a thin p-GaAs photoactive layer.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 363-366
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    High efficient radiation stable AlGaAs/GaAs solar cells with internal Bragg reflector (1995)
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    Publication Date: 2011-08-24
    Description: An investigation of solar cells based on AlGaAs/GaAs heterostructures with an internal Bragg reflector as the back-surface reflector is presented. The Bragg reflector is grown by low pressure metalorganic chemical vapor deposition on n-GaAs substrates in a horizontal resistively heated reactor. The Bragg reflector with its maximum reflectance centered at a wavelength of 860 nm consists of 12 pairs of AlAs/GaAs layers. The resulting Bragg reflector has a thickness of 0.072 micrometers for AlAs and 0.059 micrometers for GaAs. The multi-layered quasi-dielectric stack selectively reflects weakly absorbed photons with energies near to the GaAs band gap for a second pass through the photoactive region, thus increasing the photocurrent. The use of the Bragg reflector allows the external quantum efficiency to be increased in the long wavelength of the spectrum. The use of the Bragg reflector and an antireflective coating and prismatic cover allowed an efficiency of 23.4 percent to be obtained.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 367-370
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    Space concentrator solar cells based on multilayer LPE grown AlGaAs/GaAs heterostructure (1995)
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    Publication Date: 2011-08-24
    Description: The high efficiency solar cells based on multilayer AlGaAs/GaAs heterostructures, prepared by low temperature liquid phase epitaxy (LPE), were developed and tested. An investigation of the low temperature LPE process for the crystallization of AlGaAs heterostructures of as high as 24.0 to 24.7 percent under AMO conditions at concentration ratios of 20 to 100x, were reached. Developed solar cells show substantial radiation resistance to the damage induced by 3.75 MeV electrons.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: ESA, Proceedings of 4th European Space Power Conference (ESPC). Volume 2: Photovoltaic Generators, Energy Storage; p 359-362
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  • 42
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    Three-dimensional position and shape of the bow shock and their variation with Alfvenic, sonic and magnetosonic Mach numbers and interplanetary magnetic field orientation (1995)
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    Publication Date: 2011-08-24
    Description: A large set of bow shock crossings (i.e., 1392) observed by 17 spacecraft has been used to explore the three-dimensional shape and location of the Earth's bow shock and its dependence on solar wind and interplanetary magnetic field (IMF) conditions. This study investigates deviations from gas dynamic flow models associated with the magnetic terms in the magnetohydrodynamic (MHD) equations. Empirical models predicting the statistical position and shape of the bow shock for arbitrary values of the solar wind pressure, IMF, and Alfvenic Mach number (M(sub A)) have been derived. The resulting data set has been used to fit three-dimensional bow shock surfaces and to explore the variations in these surfaces with sonic (M(sub S)), Alfvenic (M(sub A)) and magnetosonic (M(sub MS)) Mach numbers. Analysis reveals that among the three Mach numbers, M(sub A) provides the best ordering of the least square bow shock curves. The subsolar shock is observed to move Earthward while the flanks flare outward in response to decreasing M(sub A); the net change represents a 6-10% effect. Variations due to changes in the IMF orientation were investigated by rotating the crossings into geocentric interplanetary medium coordinates. Past studies have suggested that the north-south extent of the bow shock surface exceeds the east-west dimension due to asymmetries in the fast mode Mach cone. This study confirms such a north-south versus east-west asymmetry and quantifies its variation with M(sub S), M(sub A), M(sub MS), and IMF orientation. A 2-7% effect is measured, with the asymmetry being more pronounced at low Mach numbers. Combining the bow shock models with the magnetopause model of Roelof and Sibeck (1993), variations in the magnetosheath thickness at different local times are explored. The ratio of the bow shock size to the magnetopause size at the subpolar point is found to be 1.46; at dawn and dusk, the ratios are found to be 1.89 and 1.93, respectively. The subsolar magnetosheath thickness is used to derive the polytropic index gamma according to the empirical relation of Spreiter et al. (1966). The resulting gamma = 2.3 suggests the empirical formula is inadequate to describe the MHD interaction between the solar wind and the magnetosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A5; p. 7907-7916
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    O(1)S 557.7nm and O(1)D 630 nm emissions in shuttle thruster plumes (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Radiation resulting from interaction between the effluent cloud of a space shuttle thruster and the ambient atmosphere was observed with a spectograph aboard the shutttle. The spectral measurements were made between 400 and 800 nm with a resolutoion of 3 nm. The primary emissions are identified as NO2, HNO, O(1)D, and O(1)S. These are the first observations od O(1)S emission in the shuttle plume. These data are compared with the previous measurements, and possible excitation mechanisms are discussed. The results are also compared with a Monte Carlo simulation of thruster plume-atmosphere interaction radiation.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; A4; p. 5819-5825
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    The response of ionospheric convection in the polar cap to substorm activity (1995)
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    Publication Date: 2011-08-24
    Description: We report multi-instrument observations during an isolated substorm on 17 October 1989. The European Incoherent Scatter (EISCAT) radar operated in the SP-UK-POLI mode measuring ionospheric convection at latitudes 71 deg Lambda - 78 deg Lambda. Sub-Auroral Magnetometer Network (SAMNET) and the EISCAT Magnetometer Cross provide information on the timing of substorm expansion phase onset and subsequent intensifications, as well as the location of the field aligned and ionospheric currents associated with the substorm current wedge. Interplanetary Monitoring Platform-8 (IMP-8) magnetic field data are also included. Evidence of a substorm growth phase is provided by the equatorward motion of a flow reversal boundary across the EISCAT radar field of view at 2130 MLT, following a southward turning of the interplanetary magnetic field (IMF). We infer that the polar cap expanded as a result of the addition of open magnetic flux in the tail lobes during this interval. The flow reversal boundary, which is a lower limit to the polar cap boundary, reached an invariant latitude equatorward of 71 deg Lambda by the time of the expansion phase onset. We conclude that the substorm onset region in the ionosphere, defined by the westward electrojet, mapped to a part of the tail radially earthward of the boundary between open and closed magnetic flux, the distant neutral line. Thus the substorm was not initiated at the distant neutral line, although there is evidence that it remained active during the expansion phase.
    Keywords: GEOPHYSICS
    Type: Annales Geophysicae (ISSN 0992-7689); 13; 2; p. 147-158
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    Journey to the end of the dinosaur era: A society expedition to Belize (1995)
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    Publication Date: 2011-08-24
    Description: The impact of the extraterrestrial object that formed the Chicxulub crater in the northwestern Yucatan peninsula of Mexico is the leading suspect for the extinction of the dinosaurs. This article reports on a Planetary Society expedition to Albion Island in the Rio Hondo region of Belize to investigate evidence supporting the impact theory.
    Keywords: GEOPHYSICS
    Type: Planetary Report (ISSN 0736-3680); 15; 4; p. 10-14
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    Vertical neutral wind in the equatorial F-region deduced from electric field and ion density measurements (1995)
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    Details
    Publication Date: 2011-08-24
    Description: Direct current (DC) electric field and ion density measurements near density depletion regions (that is, equatorial plasma bubbles) are used to estimate the vertical neutral wind speed. The measured zonal electric field in a series of density depletions crossed by the San Marco D satellite at 01.47-01.52 Universal Time (UT) on 25 October 1988, can be explained if a downward neutral wind of 15-30 m/s exists. Simultaneously, the F-region plasma was moving downward at a speed of 30-50 m/s. These events appear in the local time sector of 23.00-23.15 in which strong downward neutral winds may occur. Indeed, airglow measurements suggest that downward neutral velocities of 25-50 m/s are possible at time near midnight in the equatorial F-region.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169); 57; 6; p. 645-651
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    The electron foreshock (1995)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An overview of the observations of backstreaming electrons in the foreshock and the mechanisms that have been proposed to explain their properties will be presented. A primary characteristic of observed foreshock electrons is that their velocity distributions are spatially structured in a systematic way depending on distance from the magnetic field line which is tangent to the shock. There are two interrelated aspects to explaining the structure of velocity distributions in the foreshock, one involving the acceleration mechanism and the other, propagation from the source to the observing point. First, the source distribution of electrons energized by the shock must be determined along the shock surface. Proposed acceleration mechanisms include magnetic mirroring of incoming solar wind particles and mechanisms involving transmission of particles through the shock. Secondly, the kinematics of observable electrons streaming away from a curved shock with an initial parallel velocity and a downstream perpendicular velocity component due to the motional electric field must be determined. This is the context in which the observations and their explanations will be reviewed.
    Keywords: GEOPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 15; 8-9; p. 9-27
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    Comparison of cloud fields from atmospheric general circulation model, in situ and satellite measurements (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This paper focuses on the comparison of cloud amounts derived from an atmospheric general circulation model (AGCM), Satellite-observed clouds, and Ground-based cloud observations. Unlike Earth Radiation Budget Experiment (ERBE)-type comparisons it does not mix potential errors in the cloud amount with those in the radiation code embedded in the model. Long term cloud climatologies were used to compare global cloud amounts and regional seasonal cycles. The AGCM successfully reproduced the signatures of the warm pool and North Pacific seasonal cycle cloudiness but failed in the low stratus region off the coast of South America, a known problem for AGCMs. The data sets also reproduced the anomaly signature associated with El Nino in the warm pool region, but the model amounts were lower. Global results had a similar success rate, with the model generally producing lower total cloud compared to the satellite and in situ measurements. To compare cloud vertical distributions the cloud height may need to be validated using the corresponding radiation fields. Unfortunately there were also some large discrepancies between the two observed cloud data sets. While tremendously improved over the last decade the character of the observed cloud data sets, must be substantially enhanced before they will be useful in validating AGCMs by any but the crudest levels of comparison.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; D1; p. 1367-1378
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    Nonequilibrium Flow Expansion Experiment Around a Blunted Cone (1995)
    In:  CASI
    Details
    Publication Date: 2011-07-22
    Description: Eleven tests were carried out in DLR's high enthalpy tunnel in Goettingen (HEG), Germany, for reservoir conditions ranging from 10 to 23 MJ/kg and a free stream Mach number of approximately 10. A blunted cone model with a cylindrical afterbody (sting) was investigated. To obtain information on the influence of defined parameters on the body back flow, especially of the reacting gas, the heat transfer rate along the body contour was measured with fast response surface thermocouples on the forebody and sensitive thin film heat transfer gauges on the base and sting of the model. Flow visualization with a holographic interferometry system was provided. Tests are described, and a preliminary interpretation of the observed flow effects are given.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ESA, Proceedings of the 2nd European Symposium on Aerothermodynamics for Space Vehicles; p 383-38
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  • 50
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    The VOrtex Ring Transit EXperiment (VORTEX) GAS project (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Get Away Special (GAS) payload G-093, also called VORTEX (VOrtex Ring Transit EXperiment), is an investigation of the propagation of a vortex ring through a liquid-gas interface in microgravity. This process results in the formation of one or more liquid droplets similar to earth based liquid atomization systems. In the absence of gravity, surface tension effects dominate the drop formation process. The Shuttle's microgravity environment allows the study of the same fluid atomization processes as using a larger drop size than is possible on Earth. This enables detailed experimental studies of the complex flow processes encountered in liquid atomization systems. With VORTEX, deformations in both the vortex ring and the fluid surface will be measured closely for the first time in a parameters range that accurately resembles liquid atomization. The experimental apparatus will record images of the interactions for analysis after the payload has been returned to earth. The current design of the VORTEX payload consists of a fluid test cell with a vortex ring generator, digital imaging system, laser illumination system, computer based controller, batteries for payload power, and an array of housekeeping and payload monitoring sensors. It is a self-contained experiment and will be flown on board the Space Shuttle in a 5 cubic feet GAS canister. The VORTEX Project is entirely run by students at the University of Michigan but is overseen by a faculty advisor acting as the payload customer and the contact person with NASA. This paper summarizes both the technical and programmatic aspects of the VORTEX Project.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Goddard Space Flight Center, The 1995 Shuttle Small Payloads Symposium; p 221-229
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    Cryogenic Two-Phase Flight Experiment: Results overview (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper focuses on the flight results of the Cryogenic Two-Phase Flight Experiment (CRYOTP), which was a Hitchhiker based experiment that flew on the space shuttle Columbia in March of 1994 (STS-62). CRYOTP tested two new technologies for advanced cryogenic thermal control; the Space Heat Pipe (SHP), which was a constant conductance cryogenic heat pipe, and the Brilliant Eyes Thermal Storage Unit (BETSU), which was a cryogenic phase-change thermal storage device. These two devices were tested independently during the mission. Analysis of the flight data indicated that the SHP was unable to start in either of two attempts, for reasons related to the fluid charge, parasitic heat leaks, and cryocooler capacity. The BETSU test article was successfully operated with more than 250 hours of on-orbit testing including several cooldown cycles and 56 freeze/thaw cycles. Some degradation was observed with the five tactical cryocoolers used as thermal sinks, and one of the cryocoolers failed completely after 331 hours of operation. Post-flight analysis indicated that this problem was most likely due to failure of an electrical controller internal to the unit.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: The 1995 Shuttle Small Payloads Symposium; p 111-123
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    Experimental Results from the Thermal Energy Storage-1 (TES-1) Flight Experiment (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Thermal Energy Storage-1 (TES-1) is a flight experiment that flew on the Space Shuttle Columbia (STS-62), in March 1994, as part of the OAST-2 mission. TES-1 is the first experiment in a four experiment suite designed to provide data for understanding the long duration microgravity behavior of thermal energy storage fluoride salts that undergo repeated melting and freezing. Such data have never been obtained before and have direct application for the development of space-based solar dynamic (SD) power systems. These power systems will store solar energy in a thermal energy salt such as lithium fluoride or calcium fluoride. The stored energy is extracted during the shade portion of the orbit. This enables the solar dynamic power system to provide constant electrical power over the entire orbit. Analytical computer codes have been developed for predicting performance of a spaced-based solar dynamic power system. Experimental verification of the analytical predictions is needed prior to using the analytical results for future space power design applications. The four TES flight experiments will be used to obtain the needed experimental data. This paper will focus on the flight results from the first experiment, TES-1, in comparison to the predicted results from the Thermal Energy Storage Simulation (TESSIM) analytical computer code. The TES-1 conceptual development, hardware design, final development, and system verification testing were accomplished at the NASA lewis Research Center (LeRC). TES-1 was developed under the In-Space Technology Experiment Program (IN-STEP), which sponsors NASA, industry, and university flight experiments designed to enable and enhance space flight technology. The IN-STEP Program is sponsored by the Office of Space Access and Technology (OSAT).
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Goddard Space Flight Center, The 1995 Shuttle Small Payloads Symposium; p 31-38
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  • 53
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    Flight testing of the Capillary Pumped Loop Flight Experiment (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Capillary Pumped Loop Flight Experiment (CAPL) employs a passive two-phase thermal control system that uses the latent heat of vaporization of ammonia to transfer heat over long distances. CAPL was designed as a prototype of the Earth Observing System (EOS) instrument thermal control systems. The purpose of the mission was to provide validation of the system performance in micro-gravity, prior to implementation on EOS. CAPL was flown on STS-60 in February, 1994, with some unexpected results related to gravitational effects on two-phase systems. Flight test results and post flight investigations will be addressed, along with a brief description of the experiment design.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: The 1995 Shuttle Small Payloads Symposium; p 1-19
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  • 54
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    The Cryogenic Test Bed experiments: Cryogenic heat pipe flight experiment CRYOHP (STS-53). Cryogenic two phase flight experiment CRYOTP (STS-62). Cryogenic flexible diode flight experiment CRYOFD (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper presents an overview of the Cryogenic Test Bed (CTB) experiments including experiment results, integration techniques used, and lessons learned during integration, test and flight phases of the Cryogenic Heat Pipe Flight Experiment (STS-53) and the Cryogenic Two Phase Flight Experiment (OAST-2, STS-62). We will also discuss the Cryogenic Flexible Diode Heat Pipe (CRYOFD) experiment which will fly in the 1996/97 time frame and the fourth flight of the CTB which will fly in the 1997/98 time frame. The two missions tested two oxygen axially grooved heat pipes, a nitrogen fibrous wick heat pipe and a 2-methylpentane phase change material thermal storage unit. Techniques were found for solving problems with vibration from the cryo-collers transmitted through the compressors and the cold heads, and mounting the heat pipe without introducing parasitic heat leaks. A thermally conductive interface material was selected that would meet the requirements and perform over the temperature range of 55 to 300 K. Problems are discussed with the bi-metallic thermostats used for heater circuit protection and the S-Glass suspension straps originally used to secure the BETSU PCM in the CRYOTP mission. Flight results will be compared to 1-g test results and differences will be discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Goddard Space Flight Center, The 1995 Shuttle Small Payloads Symposium; p 21-30
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    Movement of water vapor in the atmosphere measured by an imaging spectrometer at Rogers Dry Lake, CA (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Movement of water as vapor in the atmosphere is a fundamental process in the Earth's hydrological cycle. Investigations of spatial and time scales of water vapor transport in the atmosphere are important areas of research. Water vapor transmits energy as a function of its abundance across the spectrum. This is shown in the 400- to 2500-nm spectral region where the transmission of the terrestrial atmosphere has been modeled using the MODTRAN radiative transfer code for a range of water vapor abundances. Based on these model results, spectra measured by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) have been used to investigate the movement of water vapor at 20-m spatial resolution over an 11-by-30-km area at approximately 15-minute time intervals (1.25 hours total). AVIRIS measures the upwelling spectral radiance from 400 to 2500 nm at 10-nm spectral intervals and collects images of 11-by-up-to-1000 km at 20-m spatial resolution. Data are collected at a rate of 1 km of flight line per 4.5 seconds. A set of five AVIRIS flight lines was acquired in rapid succession over Rogers Dry Lake, CA on May 18, 1993 at 18:59, 19:13, 19:29, 19:47, and 19:59 UTC. Rogers Dry lake is located 2 hours north of Los Angeles, CA at 34.84 degrees north latitude and 117.83 degrees west longitude in the Mojave Desert.
    Keywords: GEOPHYSICS
    Type: Summaries of the Fifth Annual JPL Airborne Earth Science Workshop. Volume 1: AVIRIS Workshop; p 79-82
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    Emerging CFD technologies and aerospace vehicle design (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: With the recent focus on the needs of design and applications CFD, research groups have begun to address the traditional bottlenecks of grid generation and surface modeling. Now, a host of emerging technologies promise to shortcut or dramatically simplify the simulation process. This paper discusses the current status of these emerging technologies. It will argue that some tools are already available which can have positive impact on portions of the design cycle. However, in most cases, these tools need to be integrated into specific engineering systems and process cycles to be used effectively. The rapidly maturing status of unstructured and Cartesian approaches for inviscid simulations makes suggests the possibility of highly automated Euler-boundary layer simulations with application to loads estimation and even preliminary design. Similarly, technology is available to link block structured mesh generation algorithms with topology libraries to avoid tedious re-meshing of topologically similar configurations. Work in algorithmic based auto-blocking suggests that domain decomposition and point placement operations in multi-block mesh generation may be properly posed as problems in Computational Geometry, and following this approach may lead to robust algorithmic processes for automatic mesh generation.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 359-384
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    Prospects and expectations for unstructured methods (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The last decade has witnessed a vigorous and sustained research effort on unstructured methods for computational fluid dynamics. Unstructured mesh generators and flow solvers have evolved to the point where they are now in use for design purposes throughout the aerospace industry. In this paper we survey the various mesh types, structured as well as unstructured, and examine their relative strengths and weaknesses. We argue that unstructured methodology does offer the best prospect for the next generation of computational fluid dynamics algorithms.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 273-287
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    A Cartesian, cell-based approach for adaptively-refined solutions of the Euler and Navier-Stokes equations (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A Cartesian, cell-based approach for adaptively-refined solutions of the Euler and Navier-Stokes equations in two dimensions is developed and tested. Grids about geometrically complicated bodies are generated automatically, by recursive subdivision of a single Cartesian cell encompassing the entire flow domain. Where the resulting cells intersect bodies, N-sided 'cut' cells are created using polygon-clipping algorithms. The grid is stored in a binary-tree data structure which provides a natural means of obtaining cell-to-cell connectivity and of carrying out solution-adaptive mesh refinement. The Euler and Navier-Stokes equations are solved on the resulting grids using a finite-volume formulation. The convective terms are upwinded: A gradient-limited, linear reconstruction of the primitive variables is performed, providing input states to an approximate Riemann solver for computing the fluxes between neighboring cells. The more robust of a series of viscous flux functions is used to provide the viscous fluxes at the cell interfaces. Adaptively-refined solutions of the Navier-Stokes equations using the Cartesian, cell-based approach are obtained and compared to theory, experiment and other accepted computational results for a series of low and moderate Reynolds number flows.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 207-224
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    Grid related issues for static and dynamic geometry problems using systems of overset structured grids (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Grid related issues of the Chimera overset grid method are discussed in the context of a method of solution and analysis of unsteady three-dimensional viscous flows. The state of maturity of the various pieces of support software required to use the approach is considered. Current limitations of the approach are identified.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 181-192
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  • 60
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    Grid generation: A view from the trenches (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This paper presents 'A view from the trenches' on CFD grid generation from a Pratt & Whitney perspective. We anticipate that other organizations have similar views. We focus on customer expectations and the consequent requirements. We enunciate a vision for grid generation, discuss issues that developers must recognize.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 45-54
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    Requirements for effective use of CFD in aerospace design (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper presents a perspective on the requirements that Computational Fluid Dynamics (CFD) technology must meet for its effective use in aerospace design. General observations are made on current aerospace design practices and deficiencies are noted that must be rectified for the U.S. aerospace industry to maintain its leadership position in the global marketplace. In order to rectify deficiencies, industry is transitioning to an integrated product and process development (IPPD) environment and design processes are undergoing radical changes. The role of CFD in producing data that design teams need to support flight vehicle development is briefly discussed. An overview of the current state of the art in CFD is given to provide an assessment of strengths and weaknesses of the variety of methods currently available, or under development, to produce aerodynamic data. Effectiveness requirements are examined from a customer/supplier view point with design team as customer and CFD practitioner as supplier. Partnership between the design team and CFD team is identified as an essential requirement for effective use of CFD. Rapid turnaround, reliable accuracy, and affordability are offered as three key requirements that CFD community must address if CFD is to play its rightful role in supporting the IPPD design environment needed to produce high quality yet affordable designs.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 15-28
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  • 62
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    Surface modeling and grid generation for aeropropulsion CFD (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The efforts in geometry modeling and grid generation at the NASA Lewis Research Center, as applied to the computational fluid dynamic (CFD) analysis of aeropropulsion systems, are presented. The efforts are mainly characterized by a focus on the analysis of components of an aeropropulsion system, which involve turbulent viscous flow with heat transfer and chemistry. Thus, this discussion will follow that characterization and will sequence through the components of typical propulsion systems consisting of inlets, compressors, combustors, turbines, and nozzles. For each component, some applications of CFD analysis will be presented to show how CFD is used to compute the desired performance information, how geometry modeling and grid generation are performed, and what issues have developed related to geometry modeling and grid generation. The discussion will illustrate the following needs related to geometry modeling and grid generation as observed in aeropropulsion analysis: (1) accurate and efficient resolution of turbulent viscous and chemically-reacting flowfields; (2) easy-to-use interfaces with CAD data for automated grid generation about complex geometries; and (3) automated batch grid generation software for use with design and optimization software.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 89-103
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    Combustion system CFD modeling at GE Aircraft Engines (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses key features of current combustion system CFD modeling capabilities at GE Aircraft Engines provided by the CONCERT code; CONCERT development history; modeling applied for designing engine combustion systems; modeling applied to improve fundamental understanding; CONCERT3D results for current production combustors; CONCERT3D model of NASA/GE E3 combustor; HYBRID CONCERT CFD/Monte-Carlo modeling approach; and future modeling directions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 87-97
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    The failure analysis, redesign, and final preparation of the Brilliant Eyes Thermal Storage Unit for flight testing (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper describes the engineering thought process behind the failure analysis, redesign, and rework of the flight hardware for the Brilliant Eyes Thermal Storage Unit (BETSU) experiment. This experiment was designed to study the zero-g performance of 2-methylpentane as a suitable phase change material. This hydrocarbon served as the cryogenic storage medium for the BETSU experiment which was flown 04 Mar 94 on board Shuttle STS-62. Ground testing had indicated satisfactory performance of the BETSU at the 120 Kelvin design temperature. However, questions remained as to the micro-gravity performance of this unit; potential deviations in ground (1 g) versus space flight (0 g) performance, and how the unit would operate in a realistic space environment undergoing cyclical operation. The preparations and rework performed on the BETSU unit, which failed initial flight qualification, give insight and lessons learned to successfully develop and qualify a space flight experiment.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Goddard Space Flight Center, The 1995 Shuttle Small Payloads Symposium; p 295-302
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  • 65
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    A procedure for automating CFD simulations of an inlet-bleed problem (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A procedure was developed to improve the turn-around time for computational fluid dynamics (CFD) simulations of an inlet-bleed problem involving oblique shock-wave/boundary-layer interactions on a flat plate with bleed into a plenum through one or more circular holes. This procedure is embodied in a preprocessor called AUTOMAT. With AUTOMAT, once data for the geometry and flow conditions have been specified (either interactively or via a namelist), it will automatically generate all input files needed to perform a three-dimensional Navier-Stokes simulation of the prescribed inlet-bleed problem by using the PEGASUS and OVERFLOW codes. The input files automatically generated by AUTOMAT include those for the grid system and those for the initial and boundary conditions. The grid systems automatically generated by AUTOMAT are multi-block structured grids of the overlapping type. Results obtained by using AUTOMAT are presented to illustrate its capability.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 731-749
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    Application of CFD in aeronautics at NASA Ames Research Center (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The role of Computational Fluid Dynamics (CFD) at Ames Research Center has expanded to address a broad range of aeronautical problems, including wind tunnel support, flight test support, design, and analysis. Balancing the requirements of each new problem against the available resources - software, hardware, time, and expertise - is critical to the effective use of CFD. Several case studies of recent applications highlight the depth of CFD capability at Ames, the tradeoffs involved in various approaches, and lessons learned in the use of CFD as an engineering tool.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 57-67
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    Grid generation and surface modeling for CFD (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: When computing the flow around complex three dimensional configurations, the generation of the mesh is the most time consuming part of any calculation. With some meshing technologies this can take of the order of a man month or more. The requirement for a number of design iterations coupled with ever decreasing time allocated for design leads to the need for a significant acceleration of this process. Of the two competing approaches, block-structured and unstructured, only the unstructured approach will allow fully automatic mesh generation directly from a CAD model. Using this approach coupled with the techniques described in this paper, it is possible to reduce the mesh generation time from man months to a few hours on a workstation. The desire to closely couple a CFD code with a design or optimization algorithm requires that the changes to the geometry be performed quickly and in a smooth manner. This need for smoothness necessitates the use of Bezier polynomials in place of the more usual NURBS or cubic splines. A two dimensional Bezier polynomial based design system is described.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 29-43
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    Telescience operations with the solar array module plasma interaction experiment (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Solar Array Module Plasma Interactions Experiment (SAMPIE) is a flight experiment that flew on the Space Shuttle Columbia (STS-62) in March 1994, as part of the OAST-2 mission. The overall objective of SAMPIE was to determine the adverse environmental interactions within the space plasma of low earth orbit (LEO) on modern solar cells and space power system materials which are artificially biased to high positive and negative direct current (DC) voltages. The two environmental interactions of interest included high voltage arcing from the samples to the space plasma and parasitic current losses. High voltage arcing can cause physical damage to power system materials and shorten expected hardware life. parasitic current losses can reduce power system efficiency because electric currents generated in a power system drain into the surrounding plasma via parasitic resistance. The flight electronics included two programmable high voltage DC power supplies to bias the experiment samples, instruments to measure the surrounding plasma environment in the STS cargo bay, and the on-board data acquisition system (DAS). The DAS provided in-flight experiment control, data storage, and communications through the Goddard Space Flight Center (GSFC) Hitchhiker flight avionics to the GSFC Payload Operations Control Center (POCC). The DAS and the SAMPIE POCC computer systems were designed for telescience operations; this paper will focus on the experiences of the SAMPIE team regarding telescience development and operations from the GSFC POCC during STS-62. The SAMPIE conceptual development, hardware design, and system verification testing were accomplished at the NASA Lewis Research Center (LeRC). SAMPIE was developed under the In-Space Technology Experiment Program (IN-STEP), which sponsors NASA, industry, and university flight experiments designed to enable and enhance space flight technology. The IN-STEP Program is sponsored by the Office of Space Access and Technology (OSAT).
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Goddard Space Flight Center, The 1995 Shuttle Small Payloads Symposium; p 59-72
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    Boundary layer blockage in expansion tube nozzles (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The results of a first order perfect gas correction for the effects of the boundary layer formation within expansion tubes with nozzles are presented. The analytical model developed to describe the boundary layer formation within the expansion tube and an expansion nozzle located at the end of the acceleration tube is based on the Karman integral equations. The results of this analytical model are compared with experimental data from an expansion diffuser. The model provides a useful tool for the preliminary design of nozzles for such facilities.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Shock Tunnel Studies of Scramjet Phenomena 1994; 6 p
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    Demonstration of an automated CFD system for three-dimensional flow simulations (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: In this paper the capabilities of an automated CFD system which is currently available at NLR are demonstrated. Transonic flow around the AS28G wing/body configuration and hypersonic flow through a generic three-dimensional mixed-compression airbreathing inlet are simulated. An assessment of the level of automation of the current CFD-system is made. The problem-turnaround time lies within the order of a week for both applications.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 713-730
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    Advanced Methodology for Simulation of Complex Flows Using Structured Grid Systems (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Detailed simulations of viscous flows in complicated geometries pose a significant challenge to current capabilities of Computational Fluid Dynamics (CFD). To enable routine application of CFD to this class of problems, advanced methodologies are required that employ (a) automated grid generation, (b) adaptivity, (c) accurate discretizations and efficient solvers, and (d) advanced software techniques. Each of these ingredients contributes to increased accuracy, efficiency (in terms of human effort and computer time), and/or reliability of CFD software. In the long run, methodologies employing structured grid systems will remain a viable choice for routine simulation of flows in complex geometries only if genuinely automatic grid generation techniques for structured grids can be developed and if adaptivity is employed more routinely. More research in both these areas is urgently needed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 697-710
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    The role of overset grids in the development of the general purpose CFD code (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: A discussion of the strengths and weaknesses of overset composite grid and solution technology is given, along with a sampling of current work in the area. Major trends are identified, and the observation is made that generalized and hybridized overset methods provide a natural framework for combining disparate mesh types and physics models. Because of this, the author concludes that overset methods will be the foundation for the general purpose computational fluid dynamics programs of the future.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 193-204
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    Block-structured grids for complex aerodynamic configurations: Current status (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The status of CFD methods based on the use of block-structured grids for analyzing viscous flows over complex configurations is examined. The objective of the present study is to make a realistic assessment of the usability of such grids for routine computations typically encountered in the aerospace industry. It is recognized at the very outset that the total turnaround time, from the moment the configuration is identified until the computational results have been obtained and postprocessed, is more important than just the computational time. Pertinent examples will be cited to demonstrate the feasibility of solving flow over practical configurations of current interest on block-structured grids.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 163-177
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    Overview of turbulence model development and applications at Rocketdyne (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses turbulence modeling requirements, development philosophy, and approach; two major areas of concentration (high speed and low speed turbulence modeling); high speed turbulence modeling; compressibility effects; turbulence models adapted to USA code; M = 9.2 flat plate flow; Mach 7.05 flow over axisymmetric flare; Mach 8.6 flow over cold wall edge; low speed turbulence modeling; turbulence models being assessed; turbulence model deck structure and integration with Navier-Stokes solver; nonlinear algebraic-stress model; rotation modified k-epsilon model; and Reynolds stress model.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 107-117
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    Turbulence models for gas turbine combustors (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation covers gas turbine combustor flow physics, turbulence model investigations, turbulent combustion modeling, and present status and future needs.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 79-85
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    Experience with k-epsilon turbulence models for heat transfer computations in rotating (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses geometry and flow configuration, effect of y+ on heat transfer computations, standard and extended k-epsilon turbulence model results with wall function, low-Re model results (the Lam-Bremhorst model without wall function), a criterion for flow reversal in a radially rotating square duct, and a summary.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 65-77
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    Turbulence model development and application at Lockheed Fort Worth Company (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation demonstrates that computationally efficient k-l and k-kl turbulence models have been developed and implemented at Lockheed Fort Worth Company. Many years of experience have been gained applying two equation turbulence models to complex three-dimensional flows for design and analysis.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 29-37
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    The applicability of turbulence models to aerodynamic and propulsion flowfields at McDonnell-Douglas Aerospace (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The objective of this viewgraph presentation is to evaluate turbulence models for integrated aircraft components such as the forebody, wing, inlet, diffuser, nozzle, and afterbody. The one-equation models have replaced the algebraic models as the baseline turbulence models. The Spalart-Allmaras one-equation model consistently performs better than the Baldwin-Barth model, particularly in the log-layer and free shear layers. Also, the Sparlart-Allmaras model is not grid dependent like the Baldwin-Barth model. No general turbulence model exists for all engineering applications. The Spalart-Allmaras one-equation model and the Chien k-epsilon models are the preferred turbulence models. Although the two-equation models often better predict the flow field, they may take from two to five times the CPU time. Future directions are in further benchmarking the Menter blended k-w/k-epsilon and algorithmic improvements to reduce CPU time of the two-equation model.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 47-63
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    A summary of computational experience at GE Aircraft Engines for complex turbulent flows in gas turbines (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation summarizes some CFD experience at GE Aircraft Engines for flows in the primary gaspath of a gas turbine engine and in turbine blade cooling passages. It is concluded that application of the standard k-epsilon turbulence model with wall functions is not adequate for accurate CFD simulation of aerodynamic performance and heat transfer in the primary gas path of a gas turbine engine. New models are required in the near-wall region which include more physics than wall functions. The two-layer modeling approach appears attractive because of its computational complexity. In addition, improved CFD simulation of film cooling and turbine blade internal cooling passages will require anisotropic turbulence models. New turbulence models must be practical in order to have a significant impact on the engine design process. A coordinated turbulence modeling effort between NASA centers would be beneficial to the gas turbine industry.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 39-46
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    Turbulence program for propulsion systems (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Program goals at the Center for Modeling of Turbulence and Transition (CMOTT), NASA Lewis Research Center, are (1) to develop reliable turbulence (including bypass transition) and combustion models for complex flows in propulsion systems and (2) to integrate developed models into deliverable CFD tools for propulsion systems in collaboration with industry. This viewgraph presentation covers the following topics: development of turbulence and combustion models; collaboration with industry and technology transfer; isotropic eddy viscosity models; algebraic Reynolds stress models; scalar turbulence models; second order closure models; multiple scale k-epsilon models; and PDF modeling of turbulent reacting flows.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Industry-Wide Workshop on Computational Turbulence Modeling; p 1-27
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    An assessment of unstructured grid technology for timely CFD analysis (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: An assessment of two unstructured methods is presented in this paper. A tetrahedral unstructured method USM3D, developed at NASA Langley Research Center is compared to a Cartesian unstructured method, SPLITFLOW, developed at Lockheed Fort Worth Company. USM3D is an upwind finite volume solver that accepts grids generated primarily from the Vgrid grid generator. SPLITFLOW combines an unstructured grid generator with an implicit flow solver in one package. Both methods are exercised on three test cases, a wing, and a wing body, and a fully expanded nozzle. The results for the first two runs are included here and compared to the structured grid method TEAM and to available test data. On each test case, the set up procedure are described, including any difficulties that were encountered. Detailed descriptions of the solvers are not included in this paper.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 385-400
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    Future requirements in surface modeling and grid generation (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The past ten years have seen steady progress in surface modeling procedures, and wholesale changes in grid generation technology. Today, it seems fair to state that a satisfactory grid can be developed to model nearly any configuration of interest. The issues at present focus on operational concerns such as cost and quality. Continuing evolution of the engineering process is placing new demands on the technologies of surface modeling and grid generation. In the evolution toward a multidisciplinary analysis-bascd design environment, methods developed for Computational Fluid Dynamics are finding acceptance in many additional applications. These two trends, the normal evolution of the process and a watershed shift toward concurrent and multidisciplinary analysis, will be considered in assessing current capabilities and needed technological improvements.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions; p 3-13
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    Improvements and new features in the PDF module (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses what models are used in this package and what their advantages and disadvantages are, how the probability density function (PDF) model is implemented and the features of the program, and what can be expected in the future from the NASA Lewis PDF code.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Industry-Wide Workshop on Computational Turbulence Modeling; p 269-275
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    A composition joint PDF method for the modeling of spray flames (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses an extension of the probability density function (PDF) method to the modeling of spray flames to evaluate the limitations and capabilities of this method in the modeling of gas-turbine combustor flows. The comparisons show that the general features of the flowfield are correctly predicted by the present solution procedure. The present solution appears to provide a better representation of the temperature field, particularly, in the reverse-velocity zone. The overpredictions in the centerline velocity could be attributed to the following reasons: (1) the use of k-epsilon turbulence model is known to be less precise in highly swirling flows and (2) the swirl number used here is reported to be estimated rather than measured.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 259-268
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    PDF methods for turbulent reactive flows (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Viewgraphs are presented on computation of turbulent combustion, governing equations, closure problem, PDF modeling of turbulent reactive flows, validation cases, current projects, and collaboration with industry and technology transfer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 247-257
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    Modeling of turbulent chemical reaction (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Viewgraphs are presented on modeling turbulent reacting flows, regimes of turbulent combustion, regimes of premixed and regimes of non-premixed turbulent combustion, chemical closure models, flamelet model, conditional moment closure (CMC), NO(x) emissions from turbulent H2 jet flames, probability density function (PDF), departures from chemical equilibrium, mixing models for PDF methods, comparison of predicted and measured H2O mass fractions in turbulent nonpremixed jet flames, experimental evidence of preferential diffusion in turbulent jet flames, and computation of turbulent reacting flows.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 219-230
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    Second-order closures for compressible turbulence (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses project description, turbulence models, and computational engine and results for second-order closures for compressible turbulence.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 203-217
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    Turbulence requirements of a commerical CFD code (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation gives a profile of Advanced Scientific Computing (ASC) Ltd., applications, clients and clients' needs, ASC's directions, and how the Center for Modeling of Turbulence and Transition (CMOTT) can help.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 193-202
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    Turbulence modeling needs of commercial CFD codes: Complex flows in the aerospace and automotive industries (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses the following: STAR-CD computational features; STAR-CD turbulence models; common features of industrial complex flows; industry-specific CFD development requirements; applications and experiences of industrial complex flows, including flow in rotating disc cavities, diffusion hole film cooling, internal blade cooling, and external car aerodynamics; and conclusions on turbulence modeling needs.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 171-192
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    Progress in simulating industrial flows using two-equation models: Can more be achieved with further research? (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation provides a brief review of two-equation eddy-viscosity models (TEM's) from the perspective of applied CFD. It provides objective assessment of both well-known and newer models, compares model predictions from various TEM's with experiments, identifies sources of modeling error and gives historical perspective of their effects on model performance and assessment, and recommends directions for future research on TEM's.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 155-169
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    Experiences with two-equation turbulence models (1995)
    In:  CASI
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    Description: This viewgraph presentation discusses the following: introduction to CFD Research Corporation; experiences with two-equation models - models used, numerical difficulties, validation and applications, and strengths and weaknesses; and answers to three questions posed by the workshop organizing committee - what are your customers telling you, what are you doing in-house, and how can NASA-CMOTT (Center for Modeling of Turbulence and Transition) help.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 143-153
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    Recent advances in PDF modeling of turbulent reacting flows (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation concludes that a Monte Carlo probability density function (PDF) solution successfully couples with an existing finite volume code; PDF solution method applied to turbulent reacting flows shows good agreement with data; and PDF methods must be run on parallel machines for practical use.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 119-129
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    Experience with turbulence interaction and turbulence-chemistry models at Fluent Inc. (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses (1) turbulence modeling: challenges in turbulence modeling, desirable attributes of turbulence models, turbulence models in FLUENT, and examples using FLUENT; and (2) combustion modeling: turbulence-chemistry interaction and FLUENT equilibrium model. As of now, three turbulence models are provided: the conventional k-epsilon model, the renormalization group model, and the Reynolds-stress model. The renormalization group k-epsilon model has broadened the range of applicability of two-equation turbulence models. The Reynolds-stress model has proved useful for strongly anisotropic flows such as those encountered in cyclones, swirlers, and combustors. Issues remain, such as near-wall closure, with all classes of models.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 131-142
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    Recent progress in the joint velocity-scalar PDF method (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: This viewgraph presentation discusses joint velocity-scalar PDF method; turbulent combustion modeling issues for gas turbine combustors; PDF calculations for a recirculating flow; stochastic dissipation model; joint PDF calculations for swirling flows; spray calculations; reduced kinetics/manifold methods; parallel processing; and joint PDF focus areas.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, Industry-Wide Workshop on Computational Turbulence Modeling; p 99-10
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    Single-drop reactive extraction/extractive reaction with forced convective diffusion and interphase mass transfer (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: An algorithm has been developed for time-dependent forced convective diffusion-reaction having convection by a recirculating flow field within the drop that is hydrodynamically coupled at the interface with a convective external flow field that at infinity becomes a uniform free-streaming flow. The concentration field inside the droplet is likewise coupled with that outside by boundary conditions at the interface. A chemical reaction can take place either inside or outside the droplet, or reactions can take place in both phases. The algorithm has been implemented, and for comparison results are shown here for the case of no reaction in either phase and for the case of an external first order reaction, both for unsteady behavior. For pure interphase mass transfer, concentration isocontours, local and average Sherwood numbers, and average droplet concentrations have been obtained as a function of the physical properties and external flow field. For mass transfer enhanced by an external reaction, in addition to the above forms of results, we present the enhancement factor, with the results now also depending upon the (dimensionless) rate of reaction.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, The Sixth Annual Thermal and Fluids Analysis Workshop; p 291-315
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    The Benard problem: A comparison of finite difference and spectral collocation eigen value solutions (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The application of spectral methods, using a Chebyshev collocation scheme, to solve hydrodynamic stability problems is demonstrated on the Benard problem. Implementation of the Chebyshev collocation formulation is described. The performance of the spectral scheme is compared with that of a 2nd order finite difference scheme. An exact solution to the Marangoni-Benard problem is used to evaluate the performance of both schemes. The error of the spectral scheme is at least seven orders of magnitude smaller than finite difference error for a grid resolution of N = 15 (number of points used). The performance of the spectral formulation far exceeded the performance of the finite difference formulation for this problem. The spectral scheme required only slightly more effort to set up than the 2nd order finite difference scheme. This suggests that the spectral scheme may actually be faster to implement than higher order finite difference schemes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: The Sixth Annual Thermal and Fluids Analysis Workshop; p 275-290
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    Turbulance boundary conditions for shear flow analysis, using the DTNS flow solver (1995)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The effects of different turbulence boundary conditions were examined for two classical flows: a turbulent plane free shear layer and a flat plate turbulent boundary layer with zero pressure gradient. The flow solver used was DTNS, an incompressible Reynolds averaged Navier-Stokes solver with k-epsilon turbulence modeling, developed at the U.S. Navy David Taylor Research Center. Six different combinations of turbulence boundary conditions at the inflow boundary were investigated: In case 1, 'exact' k and epsilon profiles were used; in case 2, the 'exact' k profile was used, and epsilon was extrapolated upstream; in case 3, both k and epsilon were extrapolated; in case 4, the turbulence intensity (I) was 1 percent, and the turbulent viscosity (mu(sub t)) was equal to the laminar viscosity; in case 5, the 'exact' k profile was used and mu(sub t) was equal to the laminar viscosity; in case 6, the I was 1 percent, and epsilon was extrapolated. Comparisons were made with experimental data, direct numerical simulation results, or theoretical predictions as applicable. Results obtained with DTNS showed that turbulence boundary conditions can have significant impacts on the solutions, especially for the free shear layer.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: The Sixth Annual Thermal and Fluids Analysis Workshop; p 247-262
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    Thermal neutral format based on the step technology (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The exchange of models is one of the most serious problems currently encountered in the practice of spacecraft thermal analysis. Essentially, the problem originates in the diversity of computing environments that are used across different sites, and the consequent proliferation of native tool formats. Furthermore, increasing pressure to reduce the development's life cycle time has originated a growing interest in the so-called spacecraft concurrent engineering. In this context, the realization of the interdependencies between different disciplines and the proper communication between them become critical issues. The use of a neutral format represents a step forward in addressing these problems. Such a means of communication is adopted by consensus. A neutral format is not directly tied to any specific tool and it is kept under stringent change control. Currently, most of the groups promoting exchange formats are contributing with their experience to STEP, the Standard for Exchange of Product Model Data, which is being developed under the auspices of the International Standards Organization (ISO 10303). This paper presents the different efforts made in Europe to provide the spacecraft thermal analysis community with a Thermal Neutral Format (TNF) based on STEP. Following an introduction with some background information, the paper presents the characteristics of the STEP standard. Later, the first efforts to produce a STEP Spacecraft Thermal Application Protocol are described. Finally, the paper presents the currently harmonized European activities that follow up and extend earlier work on the area.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, The Sixth Annual Thermal and Fluids Analysis Workshop; p 263-273
    Format: application/pdf
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    A Navier-Stokes boundary element solver (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Using global interpolation functions (GIF's) boundary element solutions are obtained for two-dimensional laminar flows. Two schemes are proposed for handling the convective terms. The first treats convection as a forcing function, and converts the flow equations to pseudo-Poisson equations. In the second scheme, some convective effect is incorporated into the fundamental solution used in constructing the pertinent integral equations. The lid-driven cavity flow is selected as the benchmark problem.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: The Sixth Annual Thermal and Fluids Analysis Workshop; p 233-246
    Format: application/pdf
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    Transitional flow in thin tubes for space station freedom radiator (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A two dimensional finite volume method is used to predict the film coefficients in the transitional flow region (laminar or turbulent) for the radiator panel tubes. The code used to perform this analysis is CAST (Computer Aided Simulation of Turbulent Flows). The information gathered from this code is then used to augment a Sinda85 model that predicts overall performance of the radiator. A final comparison is drawn between the results generated with a Sinda85 model using the Sinda85 provided transition region heat transfer correlations and the Sinda85 model using the CAST generated data.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center, The Sixth Annual Thermal and Fluids Analysis Workshop; p 227-232
    Format: application/pdf
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