An Experimental Investigation of Cavity Aeroacoustics and Control in Subsonic Flows PDF Download
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Author: Paul Anthony Nagle
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 140
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Author: Paul Anthony Nagle
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 140
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 273
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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:
Publisher:
ISBN:
Category :
Languages : en
Pages : 71
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Book Description
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 to 17 millions per foot. Measurements were performed for a number of injection distributions. The large amplitude oscillations measured without mass injection was successfully and totally eliminated with proper mass injection.
Author: Jesse Clayton Little
Publisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 252
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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: Ning Zhuang
Publisher:
ISBN:
Category :
Languages : en
Pages : 176
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The study of supersonic cavity flows is of interest both from fundamental fluid dynamics and practical perspectives. The complex nature of this flowfield, consisting of compressible shear layers, compression/expansion waves, and fluid-acoustic interactions, makes it a rich problem to study. A detailed experimental study of supersonic flow (M=1.5 to 2) over a range of three-dimensional rectangular cavities (L/D=1 to 5.2) was conducted. The measurements included unsteady surface pressure measurements, particle image velocimetry, and flow visualization using shadowgraph and schlieren. Large-scale structures in the shear layer and a large recirculation zone in the cavity was observed. Spatial and temporal mode switching was also observed, the nature being different for short and long cavities. The shear layer characteristics of the two cavities are very different in term of curvature and growth. Supersonic microjets were used at the leading edge of the cavities to suppress the resonance in the flow. With a minimal mass flux (0.15%), the activation of microjets led to a large reduction in cavity tones (20 dB) and overall sound pressure levels (9dB). In addition, the microjet injection enhanced the shear layer mixing and reduced the velocity fluctuation in the cavities. The significant reductions together with the low mass flux requirements make this a potentially viable technique for full-scale, practical applications.
Author: Kenneth Vaccaro (2LT, USAF.)
Publisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 172
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Author: H. E. Plumblee
Publisher:
ISBN:
Category :
Languages : en
Pages : 167
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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.
Author: Wade H. Shafer
Publisher: Springer Science & Business Media
ISBN: 1461559693
Category : Science
Languages : en
Pages : 341
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Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS)* at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dis semination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this jOint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volumes were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 40 (thesis year 1995) a total of 10,746 thesis titles from 19 Canadian and 144 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this impor tant annual reference work. While Volume 40 reports theses submitted in 1995, on occasion, certain uni versities do report theses submitted in previous years but not reported at the time.
Author: Richard Hazlewood
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
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ISBN:
Category :
Languages : en
Pages :
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