Flow Induced Oscillations in Rectangular Cavities PDF Download
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Author: Alan J. Bilanin
Publisher:
ISBN:
Category :
Languages : en
Pages : 184
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Book Description
Author: Alan J. Bilanin
Publisher:
ISBN:
Category :
Languages : en
Pages : 184
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Book Description
Author: Hanno H. Heller
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 147
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Book Description
The report presents the results of an experimental wind-tunnel study of flow-induced pressure oscillations in shallow cavities (length-to-depth ratio from 4 to 7). A variable-depth rectangular cavity was exposed to tangential flow over the open surface in the Mach-number range from 0.8 to 3, with flow stagnation pressures varying from 2 to 15 psia. The cavity was tested in an empty stage and with one or two stores. Third-octave band and narrowband fluctuating-pressure spectra were obtained at various locations within the cavity and under the approaching boundary layer; these spectra yielded information on broadband and resonant response characteristics. Information on the longitudinal and lateral energy distribution, on recirculating-flow velocities, and on temperatures within the cavity was also obtained. This information was used to develop a scheme for predicting resonant frequencies and associated pressure-mode shapes, as well as discrete-frequency and broadband pressure amplitudes.
Author: M. E. Franke
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722243487
Category :
Languages : en
Pages : 48
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Book Description
An experimental study of screen-covered cavities exposed to airflow tangent to the screen is described. The term screen refers to a thin metal plate perforated with a repetitive pattern of round holes. The purpose was to find the detailed aerodynamic and acoustic mechanisms responsible for screen-covered cavity resonance and to find ways to control the pressure oscillations. Results indicate that strong cavity acoustic resonances are created by screen orifices that shed vortices which couple resonance by choosing hole spacings such that shed vortices do not arrive at a downstream orifice in synchronization with cavity pressure oscillations. The proper hole pattern is effective at all airspeeds. It was also discovered that a reduction of orifice size tended to weaken the screen/cavity interaction regardless of hole pattern, probably because of viscous flow losses at the orifices. The screened cavities that resonated did so at much higher frequencies than the equivalent open cavity. The classical large eddy phenomenon occurs at the relatively small scale of the orifices (the excitation is typically of high frequency). The wind tunnel study was made at airspeeds from 0 to 100m/sec. The 457-mm-long by 1.09-m-high rectangular cavities had length-to-depth ratios greater than one, which is indicative of shallow cavities. The cavity screens were perforated in straight rows and columns with hole diameters ranging from 1.59 to 6.35 mm and with porosities from 2.6 to 19.6 percent. Soderman, Paul T. Ames Research Center RTOP 505-61-11...
Author: Paul Zoccola (Jr., J.)
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 200
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Book Description
Author: Louis G. Kaufman
Publisher:
ISBN:
Category : Aeroacoustics
Languages : en
Pages : 288
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Book Description
Internal weapons carriage in high performance aircraft is often adversely affected by the severe aeroacoustic environment produced with the weapons bay doors open. To obtain a better understanding of this fluid dynamic problem, basic static and oscillatory pressure data were obtained for Mach 0.6 to 3.0 flows over shallow rectangular cavities in a generic flat plate model. Cavity length to depth ratios were varied from approximately 5 to 10. Static pressure data characteristic of both open and closed cavity flows were obtained. An improved Rossiter method is presented that satisfactorily predicts the possible frequency modes within the cavity. Highest fluctuating pressure occurs on the aft bulkhead, peaking near Mach 1.5 for the conditions tested. Aeroacoustic levels are substantially reduced by installing suppression fences (spoilers) at subsonic and low supersonic conditions. Acoustic levels generally drop rapidly above Mach 1.5. (Author).
Author: William K. Blake
Publisher: Elsevier
ISBN: 0323149618
Category : Technology & Engineering
Languages : en
Pages : 459
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Book Description
Mechanics of Flow-Induced Sound and Vibration: Volume 1 discusses a broad selection of flow sources that are widely encountered in many applications of subsonic flow engineering and provides combined physical and mathematical analyses of each of these sources. It classifies each of the leading sources of vibration and sound induced by various types of fluid motion and unifies the disciplines essential to describing each source. The book considers sources such as jet noise, flow-induced tones and self-excited vibration, dipole sound from rigid and flexible acoustically compact surfaces, random vibration of flow-excited plates and cylindrical shells, cavitation noise, acoustic transmission characteristics and sound radiation from bubbly liquids, splash noise, throttling and ventilation system noises, lifting surface flow noise and vibration, and tonal and broadband sounds from rotating machinery. It also integrates the fundamentals of the subject with the many practicalities of the design of quiet vibration-free machinery. This book caters to advanced students well-versed in applied mathematics, fluid mechanics, and vibrations, strength of materials, acoustics, and statistical methods.
Author: R. C. Bauer
Publisher:
ISBN:
Category : Aeroacoustics
Languages : en
Pages : 90
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Book Description
A mathematical model was assembled from fundamental fluid dynamic relations and turbulent single-stream mixing zone relations to predict spectra, i.e., the frequency and amplitude, of unsteady pressures acting in a rectangular cavity exposed to an external flow parallel to the cavity opening. Characteristics of the approaching boundary layer are expected as inputs, thereby allowing computation of spectra for cases of mass-injection upstream of the cavity. The equations were compiled as a code (CAP) that can be run in less than 15 sec on a personal computer. Maximum dynamic loads acting on the contents of the cavity can be estimated, in addition to the primary frequencies of oscillation.
Author: Eduard Naudascher
Publisher: Routledge
ISBN: 1351447858
Category : Technology & Engineering
Languages : en
Pages : 358
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Book Description
Designed for engineers, this work considers flow-induced vibrations. It covers topics such as body oscillators; fluid loading and response of body oscillators; fluid oscillators; vibrations due to extraneously-induced excitation; and vibrations due to instability-induced excitation.
Author: Eduard Naudascher
Publisher: Courier Corporation
ISBN: 0486136132
Category : Science
Languages : en
Pages : 434
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Book Description
Despite their variety, the vibration phenomena from many different engineering fields can be classified into a relatively few basic excitation mechanisms. The classification enables engineers to identify all possible sources of excitation in a given system and to assess potential dangers. This graduate-level text presents a synthesis of research results and practical experience from disparate fields in the form of engineering guidelines. It is particularly geared toward assessing the possible sources of excitation in a flow system, in identifying the actual danger spots, and in finding appropriate remedial measures or cures. Flow-induced vibrations are presented in terms of their basic elements: body oscillators, fluid oscillators, and sources of excitation. By stressing these basic elements, the authors provide a basis for the transfer of knowledge from one system to another, as well as from one engineering field to another. In this manner, well-known theories on cylinders in cross-flow or well-executed solutions from the field of wind engineering--to name just two examples--may be useful in other systems or fields on which information is scarce. The unified approach is broad enough to permit treatment of the major excitation mechanism, yet simple enough to be of practical use.
