Some Measurements of Longitudinal Space-time Correlations of Wall Pressure Fluctuations in Turbulent Pipe Flow


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Measurements made on some of the characteristics of the turbulent pressure field at the wall of a cylindrical pipe yielded root-mean-square pressure levels, power spectra, longitudinal space-time correlations, and convection velocity over a limited range of Reynolds number. The root-mean-square pressure levels were proportional to the dynamic pressure and when nondimensionalized by use of the dynamic pressure were observed to be independent of the Reynolds number and approximately equal to 0.008 over the Reynolds number range examined. The measurements indicate the existence of an apparent downstrea c nvection of the pressure field at a rate which is approximately the mean discharge velocity of the pipe flow. The pressure field in addition to being convected was also dispersed. Estimates of the scale of the turbulence were obtained. A limited statistical analysis of the pressure time history indicates that the amplitude variation is Gaussian. (Author).




Wall-pressure Fluctuations and Pressure-velocity Correlations in a Turbulent Boundary Layer


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This experimental study was carried out at a free-stream Mach number of 0.6 and a Reynolds number per foot of 3.45 x 106. The magnitudes of the wall-pressure fluctuations agree with the Lilley-Hodgson theoretical results. Space-time correlations of the wall-pressure fluctuations generally agree with Willmarth's results for longitudinal separation distances. The convection velocity of the fluctuations is found to increase with increasing separation distances, and its significance is explained. Measurements with the longitudinal component of the velocity fluctuations indicate that the contributions to the wall-pressure fluctuations are from two regions, an inner region near the wall and an outer region linked with the intermittency.




NASA Technical Report


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Mechanics of Flow-Induced Sound and Vibration, Volume 2


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Mechanics of Flow-Induced Sound and Vibration, Volume 2: Complex Flow-Structure Interactions, Second Edition, enables readers to fully understand flow-induced vibration and sound, unifying the disciplines of fluid dynamics, structural dynamics, vibration, acoustics, and statistics in order to classify and examine each of the leading sources of vibration and sound induced by various types of fluid motion. Starting from classical theories of aeroacoustics and hydroacoustics, a formalism of integral solutions valid for sources near boundaries is developed and then broadened to address different source types, including hydrodynamically induced cavitation and bubble noise, turbulent wall-pressure fluctuations, pipe and duct systems, lifting surface flow noise and vibration, and noise from rotating machinery. Each chapter is illustrated with comparisons of leading formulas and measured data. Combined with its companion book, Mechanics of Flow-Induced Sound and Vibration, Volume 1: General Concepts and Elementary Sources, the book covers everything an engineer needs to understand flow-induced sound and vibration. This book will be a vital source of information for postgraduate students, engineers and researchers with an interest in aerospace, ships and submarines, offshore structures, construction, and ventilation. - Presents every important topic in flow-induced sound and vibration - Covers all aspects of the topics addressed, from fundamental theory, to the analytical formulas used in practice - Provides the building blocks of computer modeling for flow-induced sound and vibration
















Technical Abstract Bulletin


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Report


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