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  • 1
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    Assisting extrasolar planetary detection through the determination of stellar space orientations (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Various methods outlined for indirect planetary detection would greatly benefit (in some cases require) the determination of the planetary orbital plane, which is theoretically equivalent to the stellar equatorial plane. Determining the stellar space orientation, therefore, would greatly benefit extrasolar planetary detection. Stellar rotation periods determined from short-term variations in Ca II H and K sunspot emission are utilized together with both stellar radii measurements and Doppler-broadened spectral line profiles to get the stellar inclination to the line of sight. The clocklike on-the-plane-of-the-sky component determination utilizes the concentration of sunspot-associated plage areas at central stellar latitudes when viewed in Ca II H or K emission. One can perform Ca II H and K emission speckle interferometry to measure the clocklike angle of this stellar Ca II H and K emission band, modeling it as an elliptical intensity distribution. Both components should be determinable to within 10 deg for at least the resolvable fifth magnitude stars.
    Keywords: ASTROPHYSICS
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  • 2
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    Far infrared structure of spiral galaxies from the IRAS CPC images (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Significant extended far infrared (50 micron and 100 micron) structure was found for five face-on spiral galaxies (NGC2403, M51, M83, NGC6946, and IC342) from fourteen galaxies searched in the Infrared Astronomy Satellite (IRAS) chopped photometric channel (CPC) catalogue. Images were initially processed to remove instrumental and background artifacts, the isophotal centroids of each image determined, and multiple images of each galaxy (for each wavelength) superimposed and averaged to improve signal-to-noise. Calibration of these images was performed using IRAS survey array data. Infrared isophotes were then superimposed on optical (blue) images so that direct structural comparisons could be made.
    Keywords: ASTROPHYSICS
    Type: Interstellar Dust: Contributed Papers; p 35
    Format: application/pdf
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  • 3
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    A study of the flaring and quiescent X-ray and UV emission from II Pegasi (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An investigation has been conducted of the rotational modulation of the transition-region UV and coronal X-ray emission for the RS CVn system II Pegasi. The X-ray light curve is dominated by a strong flare detected at orbital phase, where the minimum of the photometric wave occurred. The flare parameters derived show that the flare originates with a height greater than half the stellar radius. The characteristics of the flare are similar to those of a solar two-ribbon flare; a comparison of the midtransition region density with that in the coronal region shows a very steep pressure gradient.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 251; 1, No
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  • 4
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    Rotational modulation and flares on RS CVn and BY Draconis stars. XIII - IUE spectroscopy and photometry of II Pegasi during September 1986 (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: UV spectroscopy obtained for the RS CVn star II Pegasi in September, 1986, indicates the presence of a rotational modulation effect for the Mg II h and k and O I 1305 A lines; the largest flux is observed when the primary spot concentration is nearly on the opposite hemisphere, and the rotational modulation is noted to be of opposite sense to that observed in 1981. Optical photometry shows the largest concentration of spots on one hemisphere ever observed on II Peg, implying a spot group covering over 50 percent of the projected area of one hemisphere.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 223; 1-2,; 219-226
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  • 5
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    On the quasi-conical flowfield structure of the swept shock wave-turbulent boundary layer interaction (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The swept oblique shock-wave/turbulent-boundary-layer interaction generated by a 20-deg sharp fin at Mach 4 and Reynolds number 21,000 is investigated via a series of computations using both conical and three-dimensional Reynolds-averaged Navier-Stokes equations with turbulence incorporated through the algebraic turbulent eddy viscosity model of Baldwin-Lomax. Results are compared with known experimental data, and it is concluded that the computed three-dimensional flowfield is quasi-conical (in agreement with the experimental data), the computed three-dimensional and conical surface pressure and surface flow direction are in good agreement with the experiment, and the three-dimensional and conical flows significantly underpredict the peak experimental skin friction. It is pointed out that most of the features of the conical flowfield model in the experiment are observed in the conical computation which also describes the complete conical streamline pattern not included in the model of the experiment.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-1759
    Format: text
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  • 6
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    The hypersonic shock wave-turbulent boundary layer interaction generated by a sharp fin at Mach 8.2 (1992)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A combined experimental and numerical study has been conducted on the hypersonic shock-wave turbulent-boundary layer interaction at Mach 8.2 generated by a single fin of angles alpha = 10 and 15 deg. Three models are considered: (1) the 3D compressible Reynolds-averaged Navier-Stokes (RANS) equations using the k-epsilon turbulence model, (2) the 3D RANS using the Rodi turbulence model, and (3) the conical RANS using the Baldwin-Lomax algebraic turbulence model. The computations are compared with various experimental data. The computations using models (1) and (2) show quantitatively very similar results and very good agreement with experimental data for surface pressure and skin friction. Comparison with boundary layer profiles of pitot pressure and yaw angle are also generally good, but the peak surface heat transfer is overestimated by up to 48 percent. The effect of the laminar boundary layer on the fin is restricted to the immediate vicinity of the fin surface. Conical calculations using model (3) show substantially poorer agreement with experiment.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-0747
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  • 7
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    Supersonic turbulent flow past a swept compression corner at Mach 3. II (1988)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The three-dimensional Mach 3.0 shock wave-turbulent boundary layer interaction generated by a swept compression corner whose geometry is characterized by the angle of streamwise compression angle alpha and the angle of sweep lambda is presently treated by the Baldwin-Lomax (1978) algebraic turbulent eddy viscosity model. The results obtained, and those previously derived by means of Cebeci and Smith (1974) and Jones and Launder (1972) models, are compared with experimental measurements. The rate of change of the mean kinetic energy along a streamline is investigated, and evidence is obtained that the flowfield structure is rotational and inviscid.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 88-0310
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  • 8
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    Three-dimensional shock wave-turbulent boundary layer interactions generated by a sharp fin at Mach 4 (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This paper describes a combined experimental and theoretical study of three-dimensional swept shock wave-turbulent boundary layer interactions at Mach 4 generated by a sharp fin of angles alpha equals 16 and 20 degrees. The theoretical model is the three-dimensional compressible Reynolds-averaged Navier-Stokes equations with turbulence incorporated through the algebraic eddy viscosity model of Baldwin and Lomax. Previous computations have been performed by Horstman using the Baldwin-Lomax, Cebeci-Smith and Jones Launder models. Computed results for the surface pressure, skin friction and streamline angles are compared with experiment and previous numerical results. The present results display good agreement with experimental data for surface pressure and surface flow direction. All turbulence models fail to accurately predict the peak skin friction. The computed flowfields are in agreement with many of the features of the quasi-conical flowfield model of Settles.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 91-0648
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  • 9
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    New ionization fractions for the lithium- and helium-like ionization stages of calcium and iron (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A reinterpretation of the high resolution X-ray spectra of Ca XIX and Fe XXV, observed during a solar flare on March 25, 1979, is presented. New ionization fractions for Ca XVIII, Ca XIX, Fe XXIV, and Fe XXV are used, and it is shown that the new calculations substantially change the interpretation of the spectra. It is implied that the flare plasma was ionizing during the early phases of the flare, and recombining during the decay phase.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 196
    Format: text
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  • 10
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    Supersonic turbulent flow past a 3-D swept compression corner at Mach 3 (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Experimental and theoretical studies are presented on the three-dimensional shock wave-turbulent boundary layer interaction generated by a swept compression corner at Mach 3 for compression angle of 24 deg, sweep angle of 60 deg, and Reynolds numbers from 140,000 to 900,000. Two theoretical approaches were used, both of which utilize the full mass-averaged compressible three-dimensional Navier-Stokes equations but differ in the choice of turbulence model (the Baldwin-Lomax, 1978, and the Jones-Launder, 1972, model, respectively). The features of the computed mean flow structure were found to be qualitatively the same for both the Baldwin-Lomax and Jones-Launder models.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-0551
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