An Experimental Study of Passive Control of Hypersonic Cavity Flow Oscillations PDF Download
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Author: D. S. Dolling
Publisher:
ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 140
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Book Description
An experimental study of open cavity flow has been made in a high Reynolds number, Mach 5 turbulent boundary layer. The majority of measurements made were of fluctuating wall pressures. The objectives were: (1) examine how effective changes in front and rear wall geometry were at attenuating the pressure oscillations, (2) explore how impingement of a shock wave (variable strength and position) the cavity flow, and (3) how stores (different geometries and positions) affected the cavity flow. In addition, techniques which were judged effective at attenuating pressure oscillations for the empty cavity were used with shock impingement and with stores in order to explore their effectiveness under perturbed flow conditions. The results show that vented and slotted walls, and spoilers are ineffective. A 3-D rear wall (swept in both planes and symmetric about the center line) attenuated the strongest oscillations by factors of up to 7 compared to the baseline rectangular cavity. Regardless of shock impingement position, shock strength, store position, store dimensions, store to cavity volume ratio and asymmetric store arrangement the cavity oscillation frequencies remain essentially unchanged. Based on the mean and rms Pressure distributions (whose magnitude varies substantially but whose basic shape does not change significantly) and surface flow patterns it appears that the essential flow structure also remains largely unchanged. These similarities suggest that control techniques developed for the empty cavity flow should be effective with shock impingement or store release. Tests using two passive control rear walls in perturbed cavity flow support this conclusion.
Author: D. S. Dolling
Publisher:
ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 140
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Book Description
An experimental study of open cavity flow has been made in a high Reynolds number, Mach 5 turbulent boundary layer. The majority of measurements made were of fluctuating wall pressures. The objectives were: (1) examine how effective changes in front and rear wall geometry were at attenuating the pressure oscillations, (2) explore how impingement of a shock wave (variable strength and position) the cavity flow, and (3) how stores (different geometries and positions) affected the cavity flow. In addition, techniques which were judged effective at attenuating pressure oscillations for the empty cavity were used with shock impingement and with stores in order to explore their effectiveness under perturbed flow conditions. The results show that vented and slotted walls, and spoilers are ineffective. A 3-D rear wall (swept in both planes and symmetric about the center line) attenuated the strongest oscillations by factors of up to 7 compared to the baseline rectangular cavity. Regardless of shock impingement position, shock strength, store position, store dimensions, store to cavity volume ratio and asymmetric store arrangement the cavity oscillation frequencies remain essentially unchanged. Based on the mean and rms Pressure distributions (whose magnitude varies substantially but whose basic shape does not change significantly) and surface flow patterns it appears that the essential flow structure also remains largely unchanged. These similarities suggest that control techniques developed for the empty cavity flow should be effective with shock impingement or store release. Tests using two passive control rear walls in perturbed cavity flow support this conclusion.
Author: Shiaw-wuu Perng
Publisher:
ISBN:
Category : Aerodynamics, Hypersonic
Languages : en
Pages : 260
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Book Description
Author: Mostafa Barzegar Gerdroodbary
Publisher: Butterworth-Heinemann
ISBN: 0128211407
Category : Technology & Engineering
Languages : en
Pages : 230
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Book Description
Scramjet engines are a type of jet engine and rely on the combustion of fuel and an oxidizer to produce thrust. While scramjets are conceptually simple, actual implementation is limited by extreme technical challenges. Hypersonic flight within the atmosphere generates immense drag, and temperatures found on the aircraft and within the engine can be much greater than that of the surrounding air. Maintaining combustion in the supersonic flow presents additional challenges, as the fuel must be injected, mixed, ignited, and burned within milliseconds. Fuel mixing, along with the configuration and positioning of the injectors and the boundary conditions, play a key role in combustion efficiency. Scramjets: Fuel Mixing and Injection Systems discusses how fuel mixing efficiency and the advantage of injection systems can enhance the performance of the scramjets. The book begins with the introduction of the supersonic combustion chamber and explains the main parameters on the mixing rate. The configuration of scramjets is then introduced with special emphasis on the main effective parameters on the mixing of fuel inside the scramjets. In addition, basic concepts and principles on the mixing rate and fuel distribution within scramjets are presented. Main effective parameters such as range of fuel concentration for the efficient combustion, pressure of fuel jet and various arrangement of jet injections are also explained. This book is for aeronautical and mechanical engineers as well as those working in supersonic combustion who need to know the effects of compressibility on combustion, of shocks on mixing and on chemical reactions, and vorticity on the flame anchoring. - Explains the main applicable approaches for enhancement of supersonic combustion engines and the new techniques of fuel injection - Shows how the interaction of main air stream with fuel injections can develop the mixing inside the scramjets - Presents results of numerical simulations and how they can be used for the development of the combustion engines
Author: Carolyn Leigh Thiemann
Publisher:
ISBN:
Category :
Languages : en
Pages : 87
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Book Description
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: Michael F. Martino
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704
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Author:
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 636
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Book Description
Author: Kenneth M. Nicoll
Publisher:
ISBN:
Category : Aerodynamics, Supersonic
Languages : en
Pages : 44
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Book Description
An experimental investigation was made of the recovery factor and heat-transfer distributions on a set of cone-models incorporating annular cavities. This study is the second part of a two-part program. The first section contained measurements of the pressure distributions. The results show that the recovery factor in laminar, hypersonic cavity flow is almost constant within the cavity and downstream of reattachment, and is very close to the laminar attached-flow value. In the immediate vicinity of reattachment, the recovery factor is slightly higher than this value (less than 5%). The lowest values of the heat-transfer coefficient are found on the cavity floors, where a minimum of about 10 to 20% of the attached-flow value is reached. The highest values of the heat-transfer coefficient are in the immediate vicinity of reattachment. An average reattachment heattransfer coefficient of about three times the basic cone heat-transfer coefficient was measured on one cavity model. (Author).
Author: W. A. Engblom
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: American Institute of Aeronautics and Astronautics
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 960
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