Author: Brian Tyler Brooker
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 167
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The research presented in this dissertation focuses on understanding and passively controlling the unsteadiness of the flow that occurs in cavity flows. Flow passing over a cavity generates turbulent structures that result in pressure fluctuations in the cavity that exhibits itself as noise at selected tonal frequencies. The unsteadiness and the presence of the turbulent structures can be strong enough to damage the equipment that is stored in these cavities. Understanding the flow unsteadiness and determining the means to control it is an important research area that has been undertaken over the past several decades. High speed cavity flow presents several problems when used in practical applications. At lower speeds, vibrations can be controlled with ramps and/or flaps; however, there is a current need to provide a better understanding of supersonic flow around a cavity to allow future aircraft to release payload at high speed. Most of the previous research on cavity flows has been done on rectangular cavities and has provided guidelines for determining dominant frequencies and other flow properties over a cavity. This project focuses on understanding the flow unsteadiness in more of a basic configuration, namely over an axisymmetric cavity, to eliminate the effects of the side walls on the flow development. Such research is scarce in the literature, although it is a building block in understanding the nature of the cavity flows. The results of the current research agree well with the previous research conducted on rectangular cavities. The measured tonal frequencies match the predicted Rossiter modes that are well defined for rectangular cavities. The pressure data obtained at the cavity walls has shown a decrease in sound pressure levels at the various tonal frequencies when the cavity is lengthened. It is also shown that replacing the back wall of the cavity with a half-height wall results in both positive and negative effects to the tonal frequencies. At the front wall pressure fluctuations are reduced at all cavity lengths; however, the rear wall shows significant increase in pressure fluctuations for the medium and large cavity lengths.
Author: S. Jeyakumar
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: James Joe Der
Publisher:
ISBN:
Category : Aerodynamics, Supersonic
Languages : en
Pages : 64
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Book Description
Chemical and vibrational nonequilibrium phenomena in steady inviscid flow fields are studied by the analysis of flow past curved boundaries. Possible alternative choices of the state variables to be used are considered. General features of the nonequilibrium flow are studied by examination of the mathematical properties of the nonlinear flow equations. An axisymmetric nonequilibrium flow of air through a supersonic nozzle is analyzed by means of numerical computations. The coupling effects between nonuniformity (across a nozzle section) and nonequilibrium, not taken into account in the quasi-one-dimensional flow approximation, are revealed by the present analysis.
Author: Chung-Jen John Tam
Publisher:
ISBN:
Category :
Languages : en
Pages : 242
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Author: Anoop Kumar Shukla
Publisher: Springer Nature
ISBN: 9819918944
Category : Science
Languages : en
Pages : 840
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Book Description
This volume comprises the select proceedings of the 3rd Biennial International Conference on Future Learning Aspects of Mechanical Engineering (FLAME) 2022. It aims to provide a comprehensive and broad-spectrum picture of the state-of-the-art research and development in thermal, fluids, energy and process engineering, mechatronics, control and robotics, material science and engineering, solid mechanics and structural engineering, dynamics and control, engineering design, manufacturing and industrial engineering, automobile engineering. This volume will prove a valuable resource for researchers and professionals in mechanical engineering and allied fields.
Author: Ning Zhuang
Publisher:
ISBN:
Category :
Languages : en
Pages : 176
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Book Description
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:
Publisher:
ISBN:
Category : Military research
Languages : en
Pages : 604
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Author: James Ronald Sachtschale
Publisher:
ISBN:
Category :
Languages : en
Pages : 142
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Author: Carolyn Leigh Thiemann
Publisher:
ISBN:
Category :
Languages : en
Pages : 87
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Analysis of an open cavity shear layer when exposed to different leading edge pin configurations was studied experimentally, in a blow-down high speed wind tunnel run at Mach 1.84. A non-intrusive quantitative flow measurement system, Particle Image Velocimetry, was used to study velocity and vorticity fields with and without flow control implementations. The purpose of this study was to attempt to understand and explain the flow mechanisms which cause acoustic suppression obtained using different leading edge, vertical pin configurations. The cavity had an L/D of 4.89 and each pin configuration had a varied number and placement of pins, while pin height remained a constant 1⁄2 inch. The four configurations chosen to be studied were based on the best acoustic suppression results obtained by Milne [4]. To determine and understand the physical mechanism and source of attenuation of this type of cavity flow control technique, this study looked at the acoustic spectrum, velocity vector field data as well as the changes in the velocity and vorticity fields created by each pin configuration. It was determined that a redistribution of the velocity and diffusion of the vorticity in the boundary layer was caused by altering the characteristics of the boundary layer. Vertical pin configurations at the leading edge of a cavity resulted in flow characteristics which bring about a thickening of the shear layer which diffuses the boundary layer vorticity. Certain pin configurations result in various changes in the boundary layer velocity and vorticity redistributions, affecting the shear layer diffusing the boundary layer vorticity. Configurations using staggered pin patterns generated more effectively vorticity diffusion in the shear layer, which lowered the peaks and the broadband in the SPL spectrum. Possible configurations for future testing are also recommended to further study the flow suppression mechanisms.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 542
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