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  • SPACE SCIENCES  (15)
  • AERODYNAMICS  (11)
  • Theorie
  • 1
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    Rotor wake characteristics of a transonic axial-flow fan (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 24; 1802-181
    Format: text
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  • 2
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    Vortex shedding in high-speed compressor blade wakes (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The wakes of highly loaded compressor blades are generally considered to be turbulent flows. Recent work has suggested that the blade wakes are dominated by a vortex streetlike structure. The experimental evidence supporting the wake vortex structure is reviewed. This structure is shown to redistribute thermal energy within the flowfield. The effect of the wake structure on conventional aerodynamic measurements of compressor performance is noted. A two-dimensional, time-accurate, viscous numerical simulation of the flow exhibits both vortex shedding in the wake and a lower-frequency flow instability that modulates the shedding. The numerical results are shown to agree quite well with the measurement from transonic compressor rotors.
    Keywords: AERODYNAMICS
    Type: Journal of Propulsion and Power (ISSN 0748-4658); 4; 236-244
    Format: text
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  • 3
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    The galactic radio source DR 21 at 3.3 mm. (1968)
    In:  Other Sources
    Details
    Publication Date: 2011-08-12
    Description: High intensity small diameter radio source DR 21 in Cygnus X thermal radio source complex, discussing flux and consistency with model
    Keywords: SPACE SCIENCES
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  • 4
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    Active suppression of compressor instabilities (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A strategy is proposed for controlling aerodynamic instabilities which limit the useful range of both axial and centrifugal turbomachines. Both local and global instabilities (incipient rotating stall and surge) are analyzed. A theory is developed which shows how an additional disturbance, driven from real time data measured within the machine, can be generated so as to realize a device with characteristics fundamentally different from those of the turbomachine without control; for the particular compressor analyzed, the control led to a 20 percent increase in the extent of the stable operating range. The use of structural dynamics to enhance stability is also discussed.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 86-1914
    Format: text
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  • 5
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    Rotor wake characteristics of a transonic axial flow fan (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: State of the art turbomachinery flow analysis codes are not capable of predicting the viscous flow features within turbomachinery blade wakes. Until efficient 3D viscous flow analysis codes become a reality there is therefore a need for models which can describe the generation and transport of blade wakes and the mixing process within the wake. To address the need for experimental data to support the development of such models, high response pressure measurements and laser anemometer velocity measurements have been obtained in the wake of a transonic axial flow fan rotor.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 85-1133
    Format: text
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  • 6
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    Synchrotron sources. II - Pulsars and compact extragalactic objects. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Discussion of some limitations on synchrotron models for optical pulsars and compact extragalactic objects. Using the results of a previous paper, it is shown that several existing models for the pulsar NP 0532 are inconsistent with the measured time variations and polarization of the optical emission. The possibility that the low-frequency falloffs in some extragalactic objects (PKS 2134 + 004, OQ 208, and NGC 1068) could be due to emission from particles with small pitch angles, absorption by a thermal plasma, or synchrotron self-absorption is also considered. It is found that radiation by particles with small pitch angles could explain the radio emission from PKS 2134 + 004 and OQ 208, but this process is inconsistent with the observations of NGC 1068. The absorption interpretations cannot account for the turnover in the spectrum of PKS 2134 + 004.
    Keywords: SPACE SCIENCES
    Type: Astrophysical Journal; 183; July 15
    Format: text
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  • 7
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    Synchrotron sources. I - Extension of theory for small pitch angles. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Some of the features of synchrotron radiation are examined which occur when relativistic particles move at small pitch angles in a magnetic field. The emission from individual particles is computed. The general properties of the emission from distributions of particles with small pitch angles is discussed, and the emissivities and degrees of polarization for several specific source models are presented. For sources which mainly contain particles with small pitch angles, the degree of circular polarization will normally be high, whereas, if the magnetic field is somewhat irregular, the degree of linear polarization will be small. If the particle distribution also has a low-energy cutoff, the emissivity will vary linearly with frequency at low frequencies.
    Keywords: SPACE SCIENCES
    Type: Astrophysical Journal; 183; July 15
    Format: text
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  • 8
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    Some aspects of cosmic synchrotron sources (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Synchrotron emission is considered from individual particles which have small pitch angles and the general properties of synchrotron sources which mainly contain such particles, as well as the emissivities and degrees of circular polarization for specific source distributions. The limitation of synchrotron source models for optical pulsars and compact extragalactic objects are discussed, and it is shown that several existing models for the pulsar NP 0532 are inconsistent with the measured time variations and polarizations of the optical emission. Discussion is made also of whether the low frequency falloffs in the extragalactic objects PKS 2134 + 004, OQ 208, and NGC 1068 is due to emission from particles with small pitch angles or absorption by a thermal plasma or synchrotron self-absorption. It is concluded that the absorption interpretations cannot account for the turnover in the spectrum of PKS 2134 + 004. Measurements of polarization, angular structure, and X-ray flux are also described.
    Keywords: SPACE SCIENCES
    Type: NASA-CR-131526 , SUIPR-435
    Format: application/pdf
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  • 9
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    Quasi-stellar radio sources - 88-GHz flux measurements. (1968)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: 88 GHz flux measurements confirm flat or turned-up nature of quasi-stellar radio sources HF spectra
    Keywords: SPACE SCIENCES
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  • 10
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    Quantitative density visualization in a transonic compressor rotor (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The flow in a 59-cm-diameter high-work transonic compressor rotor has been visualized using a fluorescent gas, 2,3, butanedione, as a tracer. The technique allows the three-dimensional flow to be imaged as a set of distinct planes. Quantitative static density maps were obtained by correcting the images for distortion and nonlinearities introduced by the illumination and imaging systems. These images and maps were used to analyze the three-dimensional nature of the blade's boundary layer and shock system.
    Keywords: AERODYNAMICS
    Format: text
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