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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and computational fluid dynamics 6 (1994), S. 323-340 
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A new technique for the numerical analysis of aerodynamic noise generation is developed. The approach involves first solving for the time-dependent incompressible flow for the given geometry. A “hydrodynamic” density correction to the constant incompressible density is then calculated from knowledge of the incompressible pressure fluctuations. The compressible flow solution is finally obtained by considering perturbations about the “corrected” incompressible flow. This fully nonlinear technique, which is tailored to extract the relevant acoustic fluctuations, appears to be an efficient approach to the numerical analysis of aerodynamic noise generation, particularly in viscous flows. Applications of this technique to some classical acoustic problems of interest, including some with moderately high subsonic Mach numbers, are presented to validate the approach. The technique is then applied to a fully viscous problem where sound is generated by the flow dynamics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 5 (1968), S. 37-53 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Die Reaktion von Platten auf Erregung durch ein bewegtes Vielmassensystem wird mit Hilfe einer Methode, die auf derFourier-Transformation beruht, untersucht. Dieses Problem war für viele Jahre von theoretischem Interesse. Es ist aber auch für den praktisch arbeitenden Ingenieur von fundamentaler Bedeutung. Die in dieser Arbeit angegebene Methode ist allgemein, so daß das Verhalten der Platten gegenüber einem bewegten Vielkraftsystem als ein Sonderfall dieser Betrachtungen erscheint. Die Konvergenz der Lösung wurde geprüft und die numerischen Ergebnisse der ersten und zweiten Näherung wurden im speziellen Fall berechnet und in Kurvenform aufgetragen. Die Analyse zeigt, daß für die gleiche Eigenfrequenz der Platte die Resonanz bei Betrachtung eines bewegten Vielmassensystems früher erreicht wird als durch ein Vielkraftsystem. Man kann also auch sagen, daß die Eigenfrequenz bei einem bewegten Vielmassensystem niedriger ist als jene bei einem bewegten Vielkraftsystem. Diese Schlußfolgerung ist von vitaler Bedeutung, da die Reaktion auf eine bewegte Kraft als Näherung für die Reaktion auf eine bewegte Masse nicht nur gefährlich, sondern auch tragisch sein kann.
    Notes: Summary A method, based on theFourier-transform technique, is presented in order to solve the problem concerning the response of the plates to a moving multimasses system. This problem was of interest in the theory for many years; however, it is of a fundamental importance for a working engineer in the field. The method presented in this paper is general, so that the response of the plates to the moving multi-forces system, appears as a special case of this study. The convergence of the solution has been examined and the numerical results for the first and second approximations, of the special case, have been calculated and plotted. The analysis shows that for the same natural frequency of the plate, the resonance is reached prior by considering the moving multi-masses system than by moving multi-force system; i.e., the natural frequency of the moving multi-masses system is lower than that of the moving multi-forces system. This conclusion is of a vital importance, since the response of the moving force as an approximation for the response of the moving mass can be not only dangerous but also tragic.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 1968-03-01
    Print ISSN: 0001-5970
    Electronic ISSN: 1619-6937
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 4
    Publication Date: 1994-10-01
    Print ISSN: 0935-4964
    Electronic ISSN: 1432-2250
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 5
    Publication Date: 1984-01-01
    Print ISSN: 0031-9171
    Topics: Physics
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  • 6
    facet.materialart.
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    In:  Other Sources
    Publication Date: 2011-08-24
    Keywords: ACOUSTICS
    Type: AIAA Journal (ISSN 0001-1452); 30; 312-317
    Format: text
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  • 7
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2011-08-24
    Description: A novel method for the numerical analysis of aerodynamic noise generation is presented. The method involves first solving for the time-dependent incompressible flow for the given geometry. This fully nonlinear method that is tailored to extract the relevant acoustic fluctuations seems to be an efficient approach to the numerical analysis of aerodynamic noise generation.
    Keywords: ACOUSTICS
    Type: In: DGLR(AIAA Aeroacoustics Conference, 14th, Aachen, Germany, May 11-14, 1992, Proceedings. Vol. 1 (A93-19126 05-71); p. 448-456.
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  • 8
    Publication Date: 2011-08-19
    Description: An additional source of bias and uncertainty in digital spectral estimates near the Nyquist frequency is discovered which is produced by the fact that the finite width main lobe of the spectral window is periodic with period of 2(omega sub c), equal to 4pi times the Nyquist frequency. For estimates near omega sub c, contributions from frequencies near -(omega sub c) are found to appear even for a sufficiently sampled bandlimited time history. In real-world applications, this source should be significant if the number of data points is small, and it should be of even more importance if the signal is not strictly bandlimited.
    Keywords: STATISTICS AND PROBABILITY
    Type: Journal of Sound and Vibration (ISSN 0022-4650); 110; 533-537
    Format: text
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  • 9
    Publication Date: 2011-08-19
    Description: The field of computational aeroacoustics (CAA), in which sound generation by unsteady flows is calculated from first principles, has recently emerged as a viable discipline. This paper describes one CAA technique which has been validated for low Mach number, low Reynolds number, two-dimensional flows. Results of its application to geometries producing both dipole and quadrupole type sound sources are presented along with theoretical and experimental comparisons. In addition, the future promise of this and other CAA techniques in removing the present limitations is evaluated.
    Keywords: ACOUSTICS
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  • 10
    Publication Date: 2011-08-18
    Description: The motion of two and four rectilinear vortices inside a cylindrical pipe is studied under the restriction that the total circulation be zero. In the two-vortex case, it is shown that the motion is always periodic and an expression for the period is derived. In the four-vortex case, the motion is determined not to be periodic in general. However, a class of solutions where the motion is periodic is found. Several sample calculations of the vortex motion are included.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 27; 1583-158
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