Census of India, 1971
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Page : pages
File Size : 10,65 MB
Release : 1973
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Page : pages
File Size : 10,65 MB
Release : 1973
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Author : Kenneth Vaccaro (2LT, USAF.)
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Page : 172 pages
File Size : 44,6 MB
Release : 1974
Category : Aerodynamic load
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Author : Valentine Korah
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Page : 2354 pages
File Size : 10,96 MB
Release : 1994
Category : Antitrust law
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Page : 1220 pages
File Size : 37,95 MB
Release : 1976
Category : Science
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Page : 1056 pages
File Size : 12,89 MB
Release : 1977
Category : Research
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Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.
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Page : 1052 pages
File Size : 31,36 MB
Release : 1976
Category : Government reports announcements & index
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Page : 273 pages
File Size : 14,21 MB
Release : 1995
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The research presented in this report has been directed to study the effects of mass injection into the flow upstream of a cavity to understand the weapon bay cavity's flow field and its aeroacoustics. The objective also was to control the development of upstream boundary layer, and therefore, to control the development of the shear layer over the cavity. Control of the shear layer has enabled us to significantly reduce or to fully eliminate the weapons bay's aeroacoustic interactions. This study was performed in a wind tunnel at several nominal Mach numbers between 0.5 to 1.8 and at unit Reynolds numbers up. (AN).
Author : Jesse Clayton Little
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Page : 252 pages
File Size : 35,16 MB
Release : 2005
Category : Aerodynamic load
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Abstract: Grazing flow over a shallow cavity is characterized by a shear layer instability feedback loop that induces strong pressure fluctuations at discrete frequencies. Examples include flow over aircraft weapons bays, aircraft landing gear openings and transmission or reception optical ports on aircraft. In the first application, this behavior can result in decreased accuracy of weapons delivery, fatigue failures and lowered efficiencies. Because of the variety of unwanted effects inherent to cavity flows, their control is of interest to both military and commercial aircraft applications. The complex nature of cavity flow has been explored since the mid-20th century with accelerated study over the past 25 years in hopes of understanding and controlling major pressure fluctuations within the cavity. A key to developing a successful control scheme for this fluidic system is a detailed understanding of the physics that govern the flow-acoustic coupling mechanisms. This work provides both qualitative and quantitative measurements for use in characterizing the fluid and acoustic physics that govern the resonance phenomenon. Focus is placed on the subsonic regime with an emphasis on Mach 0.30 flow and its control. Results include the analysis of surface pressure spectra and spatial correlations, flow visualization and velocity measurement using particle image velocimetry (PIV) in various controlled and baseline (unforced) cases. These results show that a well chosen actuation scheme at or near the receptivity region of the cavity shear layer can interrupt or weaken the acoustic feedback loop and significantly reduce the sound pressure level in the cavity. Physically, this amounts to modifying the development and evolution of the coherent structures spanning the cavity and thereby changing the frequency at which these vortices impact the trailing edge of the geometry. In addition, simultaneous dynamic surface pressure and planar velocity measurements are used in low dimensional modeling for closed-loop controller design purposes. Modeling using this method allows design of accurate models from experimental results rather than relying on numerical data, which is incapable of resolving the complex nonlinear production of acoustics in the low subsonic cavity flows at this time.
Author : Paul Anthony Nagle
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Page : 140 pages
File Size : 30,88 MB
Release : 1995
Category : Aerodynamics
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Author : H. E. Plumblee
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Page : 167 pages
File Size : 31,58 MB
Release : 1962
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Theory is developed for the resonant frequencies and pressure amplifications of a rectangular cavity of arbitrary dimensions in a flow field. An intermediate step involves the derivation of radiation impedance for a cavity at all Mach numbers, using the concepts of retarded pot ntial t eory. Experim ntal results are given for small cavities tested in the subsonic regime and for cavities up to 8 in. in length at supersonic Mach numbers from 1.75 to 5 0. Comparisons are drawn between theoretical and experimental frequency and amplitude response, indicating that the theory developed gives very good definition of the problem.