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  • 1
    Publikationsdatum: 2005-11-27
    Beschreibung: Mathematical model for investigating radiation of noise generated by rotating blades in circular duct
    Schlagwort(e): AIRCRAFT
    Materialart: L. METHODS IN AIRCRAFT AERODYN. 1970; P 323-334
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2006-03-27
    Beschreibung: Some of the principal results obtained in three series of measurements of fluctuating surface pressures induced on externally blown flaps by jet impingment are presented. Large- and small-scale models and hot- and cold-flow tests are considered. The discussion sets forth scaling parameters and consistent features of the root-mean-square values and spectra of the loading. Implications of these results with regard to sonic fatigue are indicated.
    Schlagwort(e): AERODYNAMICS
    Materialart: STOL Technol.; p 131-142
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2011-08-16
    Beschreibung: This paper is concerned with the effect of changes in duct wall acoustic properties on the transmission of sound through ducts. Two special problems are considered. The first problem is that of a rectangular infinite-length duct with airflow and a single change in duct wall acoustic admittance. The second problem is that of an axisymmetric field in a finite circular duct without airflow and with an arbitrary number of duct wall acoustic admittance changes. Results for the first problem show the effect of wall admittance change and flow on the acoustic power transmission within the duct. Results for the second problem show the interactive effects of multiple duct liner sections on power radiated from a finite duct.
    Schlagwort(e): PHYSICS, GENERAL
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2013-08-31
    Beschreibung: Conformal mapping to determine additional mass of scalloped and clustered cylinders
    Schlagwort(e): MATHEMATICS
    Materialart: NASA-TN-D-1373
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2012-05-23
    Beschreibung: High-lift wing concepts being considered for application to commercial STOL transports are discussed. The flow patterns which produce dynamic loads on these wings are indicated. Measurements of surface pressure and acceleration on a one-half-scale model of an externally blown double-slotted flap are reported. Root-mean-square values, power spectra, and scaling parameters are shown.
    Schlagwort(e): AIRCRAFT
    Materialart: AGARD Symp. on Acoustic Fatigue; 9 p
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2011-08-18
    Beschreibung: The effects of translatory and rotational motion and of the proximity of ground surface on the radiation from acoustic monopole and dipole sources are discussed together with the key equations. It is shown that interference patterns are produced by reflection and absorption at a plane surface and that consequently, the far-field directivity of an acoustic source near the ground can be substantially altered from its free-field value. The kinematic effects discussed include the beaming of sound in the direction of source motion and the shifting of the observer source frequency in a directionally dependent manner. The effects are illustrated by experimental data.
    Schlagwort(e): ACOUSTICS
    Materialart: Noise Control Engineering; 14; Mar
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2016-06-07
    Beschreibung: The progress in propulsion system noise reduction is reviewed. The noise technology areas discussed include: fan noise; advances in suppression including conventional acoustic treatment, high Mach number inlets, and wing shielding; engine core noise; flap noise from both under-the-wing and over-the-wing powered-lift systems; supersonic jet noise suppression; and the NASA program in noise prediction.
    Schlagwort(e): AIRCRAFT PROPULSION AND POWER
    Materialart: Aeron. Propulsion; p 1-63
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2017-10-02
    Beschreibung: The radiation properties of acoustic monopoles and dipoles are described, as well as the directivity of radiation from these sources in a free field and in the presence of an absorptive surface. The kinematic effects on source radiation due to translation and rotation are discussed. Experimental measurements of sound from an acoustic monopole in motion and the characteristics of helicopter rotor and propeller noise are reviewed. Several essential concepts required by noise control engineers making measurements of noise from moving sources in the proximity of the ground are introduced.
    Schlagwort(e): ACOUSTICS
    Materialart: AGARD Special Course on Acoustic Wave Propagation; 11 p
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2017-10-02
    Beschreibung: The fundamentals of diffraction theory were reviewed and applied to several problems of aircraft noise generation, propagation, and measurement. The general acoustic diffraction problem is defined and the governing equations were set down. Diffraction phenomena are illustrated using the classical problem of the diffraction of a plane wave by a half-plane. Infinite series and geometric acoustic methods for solving diffraction problems are described. Four applications of diffraction theory are discussed: the selection of an appropriate shape for a microphone, the use of aircraft wings to shield the community from engine noise, the reflection of engine noise from an aircraft fuselage, and the radiation of trailing edge noise.
    Schlagwort(e): ACOUSTICS
    Materialart: AGARD Special Course on Acoustic Wave Propagation; 12 p
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 2019-05-24
    Beschreibung: Oscillating air pressures within cylindrical chamber containing sinusoidally driven circular piston on end wall
    Schlagwort(e): FLUID MECHANICS
    Materialart: NASA-RP-422
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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