Download or read book Jet Noise Shielding from Airframe Surfaces written by Salvador Mayoral and published by . This book was released on 2010 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigates the potential suppression of jet noise by airframe surface shielding with application to the Hybrid Wing Body aircraft (HWB). Subscale experiments utilized a bypass-ratio-10 (BPR10) turbofan nozzle that operated at realistic cycle conditions using helium-air mixture jets. The shielding surface was a flat plate shaped in the form of a generic HWB and featured vertical fins and an adjustable elevator. Chevrons and porous wedge fan flow deflectors were incorporated into the baseline nozzle to restructure and alter the jet noise source distribution. Acoustic measurements of the unshielded and shielded jets were conducted inside an anechoic chamber using a 24-microphone apparatus composed of two polar arrays, each consisting of twelve condenser microphones. One polar array was mounted at an azimuth angle [straight phi] = 0° (downward) while the second array was mounted at [straight phi] = 60° (sideline). Noise source distribution measurements were performed by densely grouping twenty-four microphones on a linear array in the downward direction. Surveys of the jet mean flow were conducted with a fully automated three-dimensional Pitot rake traverse. The Pitot rake consists of five high-resolution Pitot probes that measure the local jet total pressure. The potential for noise suppression was quantified in terms of the estimated Effective Perceived Noise Level (EPNL), a noise metric used in aircraft certification. Acoustic results of the baseline BPR10 nozzle with the HWB shield yielded only marginal EPNL reductions, even when the engine was translated two fan diameters upstream of its nominal location. Using the estimated cumulative (downward plus sideline) EPNL reduction as a figure of merit, shielding of the baseline nozzle with the nominal shield configuration yielded a 2.5 dB reduction. Acoustic imaging of the baseline jet noise source revealed that the large fan diameter, inherent to the high bypass ratio, created a long noise source region. The integration of nozzle devices significantly improved EPNL reduction with the engine positioned at its nominal location. Application of the aggressive chevrons increased the reduction to 6.5 dB, while the best wedge configuration improved this value to 6.9 dB. Combination of wedge and aggressive chevrons yielded a benefit of 7.6 dB. Examination of high-definition noise source maps showed a direct link between insertion loss and axial location of the peak noise. Ultimately, the enhanced shielding effect from the nozzle devices resulted from translation of peak intensities upstream closer to the nozzle plug. Thus the compaction and/or redistribution of the noise source via nozzle devices are essential for effective jet noise shielding on the HWB. A proposed correlator for the noise reduction due to shielding is the average illumination angle. The average illumination angle is defined as the average angular sector between noise source and observer not intercepted by the shield. For average illumination angles less than 45 deg, the EPNL reduction exceeds 3 dB. A correlation between the acoustic and mean flow results reveal that the mean velocity field by itself cannot provide useful information for inferring the noise source location.
Download or read book Federal Aircraft Noise Research Development and Demonstration Programs FY73 FY75 written by Interagency Aircraft Noise Research Panel and published by . This book was released on 1975 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technology for Aircraft Noise Reduction written by United States. Congress. House. Committee on Science, Space, and Technology. Subcommittee on Transportation, Aviation, and Materials and published by . This book was released on 1991 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Database of Inlet and Exhaust Noise Shielding for Wedge shaped Airframe written by Carl H. Gerhold and published by . This book was released on 2001 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experiment to measure the noise shielding of the blended wing body design concept was developed using a simplified wedge-shaped airframe. The experimental study was conducted in the Langley Anechoic Noise Research facility. A wideband, omnidirective sound source in a simulated engine nacelle was held at locations representative of a range of engine locations above the wing. The sound field around the model was measured, with the airframe and source in place and with source alone, using an array of microphones on a rotating hoop that is also translated along an axis parallel to the airframe axis. The insertion loss was determined from the difference between the two resulting contours. Although no attempt was made to simulate the noise characteristics of a particular engine, the broadband noise source radiated sound over a range of scaled frequencies encompassing 1 and 2 times the blade passage frequency representative of a large, high-bypass-ratio turbofan engine.
Download or read book Prediction of Jet Noise Shielding with Forward Flight Effects written by Salvador Mayoral and published by . This book was released on 2013 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aircraft noise continues to be a major concern among airport-neighboring communities. A strong component of aircraft noise is the jet noise that is generated from the turbulent mixing between the jet exhaust and ambient medium. The hybrid wing body aircraft suppresses jet noise by mounting the engines over-the-wing so that the airframe may shield ground observers from jet noise sources. Subscale jet noise shielding measurements of a scaled-down turbofan nozzle and a model of the hybrid wing body planform are taken with two 12-microphone polar arrays. Chevrons and wedge-type fan flow deflectors are integrated into the baseline bypass ratio 10 (BPR10) nozzle to modify the mean flow and alter the noise source behavior. Acoustic results indicate that the baseline BPR10 nozzle produces a long noise source region that the airframe has difficulty shielding, even when the nozzle is translated two fan diameters upstream of its nominal position. The integration of either chevrons or fan flow deflectors into the nozzle is essential for jet noise shielding because they translate peak intensities upstream, closer to the fan exit plane. The numerical counterpart of this study transforms the system of equations governing the acoustic diffraction with forward flight into the wave equation. Two forward flight formulations are considered: uniform flow over slender body; and non-uniform potential flow at low Mach number. The wave equation is solved numerically in the frequency domain using the boundary element method. The equivalent jet noise source is modeled using the combination of a wavepacket and a monopole. The wavepacket is parameterized using the experimental far-field acoustic autospectra of the BPR10 jets and knowledge of their peak noise locations. It is shown that the noise source compacts with increasing Mach number and consequently there is an increase in shielding. An assessment of the error associated with the non-uniform formulation for forward flight shows that the error is low for Mach numbers less than or equal to 0.2, but can be on the same scale as the acoustic scatter field when the Mach number is 0.6.
Download or read book The Airframe Noise Reduction Challenge written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-11 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: The NASA goal of reducing external aircraft noise by 10 dB in the near-term presents the acoustics community with an enormous challenge. This report identifies technologies with the greatest potential to reduce airframe noise. Acoustic and aerodynamic effects will be discussed, along with the likelihood of industry accepting and implementing the different technologies. We investigate the lower bound, defined as noise generated by an aircraft modified with a virtual retrofit capable of eliminating all noise associated with the high lift system and landing gear. However, the airframe noise of an aircraft in this 'clean' configuration would only be about 8 dB quieter on approach than current civil transports. To achieve the NASA goal of 10 dB noise reduction will require that additional noise sources be addressed. Research shows that energy in the turbulent boundary layer of a wing is scattered as it crosses trailing edge. Noise generated by scattering is the dominant noise mechanism on an aircraft flying in the clean configuration. Eliminating scattering would require changes to much of the aircraft, and practical reduction devices have yet to receive serious attention. Evidence suggests that to meet NASA goals in civil aviation noise reduction, we need to employ emerging technologies and improve landing procedures; modified landing patterns and zoning restrictions could help alleviate aircraft noise in communities close to airports.Lockard, David P. and Lilley, Geoffrey M.Langley Research CenterAEROACOUSTICS; AIRFRAMES; AIRCRAFT NOISE; NOISE REDUCTION; AIRCRAFT CONFIGURATIONS; WINGS; FLAPS (CONTROL SURFACES); VORTICES; TRAILING EDGES
Download or read book Noise Reduction Technology written by United States. Congress. House. Committee on Science and Technology. Subcommittee on Transportation, Aviation, and Materials and published by . This book was released on 1985 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aircraft Noise written by Oleksandr Zaporozhets and published by CRC Press. This book was released on 2011-05-13 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aircraft noise has adverse impacts on passengers, airport staff and people living near airports, it thus limits the capacity of regional and international airports throughout the world. Reducing perceived noise of aircraft involves reduction of noise at source, along the propagation path and at the receiver. Effective noise control demands highly s
Download or read book Aviation Noise Impact Management written by Laurent Leylekian and published by Springer. This book was released on 2022-03-15 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book provides a view into the state-of-the-art research on aviation noise and related annoyance. The book will primarily focus on the achievements of the ANIMA project (Aviation Noise Impact Management through Novel Approaches), but not exclusively. The content has a broader theme in order to encompass. regulation issues, the ICAO (International Civil Aviation Organization) balanced approach, progresses made on technologies and reduction of noise at source, impact of possible future civil supersonic aircraft, land-use planning issues, as well as the core topics of the ANIMA project, i.e. impact on human beings, annoyance, quality of life, health and findings of the project in this respect. This book differs from traditional research programmes on aviation noise as the authors endeavour, not to lower noise at source, but to reduce the annoyance. This book examines these non-acoustic factors in an effort to help those most affected by aviation noise – communities living close to airports, and also help airport managers, policy-makers, local authorities and researchers to deal with this issue holistically. The book concludes with some recommendations for EU, national and local policy-makers, airport and aviation authorities, and more broadly a scientifically literate audience. These recommendations may help to identify gaps for progress in terms of research but also genuine implementation actions for political and regulatory authorities.
Download or read book Aeroacoustics of Supersonic Jet Interacting with Solid Surfaces and Its Suppression written by Seyyed Saman Salehian and published by . This book was released on 2020 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The noise generated by supersonic jet is of primary interest in the high-speed flight. In several flight conditions jet exhaust of the propulsion system interacts with solid surfaces. For example, jet impingement on ground for a rocket lift-off, or interactions influenced by the integration of the engine with the airframe. Such complex applications require consideration of the role of acoustic-surface interactions on the noise generation of the jet and its radiation. Numerical analysis of supersonic jet noise involved in these scenarios is investigated by employing Hybrid Large Eddy Simulation - Unsteady Reynolds Averaged Simulation approach to model turbulence. First, the supersonic impinging jet noise reduction using aqueous injectors is investigated. The technique employed to suppress impingement noise, involves injecting liquid water from the ground surface. The Volume of Fluid model is adopted to simulate the two phase flow. The flow field and acoustic results agree well with the existing experimental data. The possible mechanisms of noise reduction by water injection are investigated. Second, supersonic jet noise reduction by employing the shielding effect of a flat plate parallel to the jet is investigated. The numerical simulations model the shielding effect of the flat plate on the acoustics of supersonic jet, and results agree with the corresponding experimental data. The physical mechanisms involved in the flow-surface interactions are investigated. With understanding these mechanisms, a slightly wavy plate is proposed including theoretical background to determine the parameters needed for the way wall to provide acoustic reduction efficiently. Results show that the proposed wavy shield can effectively reduce both the level and extent of the jet noise source as compared to that of a flat shield."--Abstract.
Download or read book Federal Aircraft Noise Research Development and Demonstration Programs FY73 FY75 written by Interagency Aircraft Noise Research Panel and published by . This book was released on 1975 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aircraft Noise Abatement written by United States. Congress. House. Committee on Science and Astronautics. Subcommittee on Aeronautics and Space Technology and published by . This book was released on 1974 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Federal Aircraft Noise Abatement Plan written by United States. Office of Noise Abatement and published by . This book was released on 1970 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Future Propulsion Systems and Energy Sources in Sustainable Aviation written by Saeed Farokhi and published by John Wiley & Sons. This book was released on 2020-01-21 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive review of the science and engineering behind future propulsion systems and energy sources in sustainable aviation Future Propulsion Systems and Energy Sources in Sustainable Aviation is a comprehensive reference that offers a review of the science and engineering principles that underpin the concepts of propulsion systems and energy sources in sustainable air transportation. The author, a noted expert in the field, examines the impact of air transportation on the environment and reviews alternative jet fuels, hybrid-electric and nuclear propulsion and power. He also explores modern propulsion for transonic and supersonic-hypersonic aircraft and the impact of propulsion on aircraft design. Climate change is the main driver for the new technology development in sustainable air transportation. The book contains critical review of gas turbine propulsion and aircraft aerodynamics; followed by an insightful presentation of the aviation impact on environment. Future fuels and energy sources are introduced in a separate chapter. Promising technologies in propulsion and energy sources are identified leading to pathways to sustainable aviation. To facilitate the utility of the subject, the book is accompanied by a website that contains illustrations, and equation files. This important book: Contains a comprehensive reference to the science and engineering behind propulsion and power in sustainable air transportation Examines the impact of air transportation on the environment Covers alternative jet fuels and hybrid-electric propulsion and power Discusses modern propulsion for transonic, supersonic and hypersonic aircraft Examines the impact of propulsion system integration on aircraft design Written for engineers, graduate and senior undergraduate students in mechanical and aerospace engineering, Future Propulsion Systems and Energy Sources in Sustainable Aviation explores the future of aviation with a guide to sustainable air transportation that includes alternative jet fuels, hybrid-electric propulsion, all-electric and nuclear propulsion.
Download or read book Advances in Effective Flow Separation Control for Aircraft Drag Reduction written by Ning Qin and published by Springer Nature. This book was released on 2019-10-17 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the results of a European-Chinese collaborative research project, Manipulation of Reynolds Stress for Separation Control and Drag Reduction (MARS), including an analysis and discussion of the effects of a number of active flow control devices on the discrete dynamic components of the turbulent shear layers and Reynolds stress. From an application point of view, it provides a positive and necessary step to control individual structures that are larger in scale and lower in frequency compared to the richness of the temporal and spatial scales in turbulent separated flows.
Download or read book Aircraft Noise written by Oleksandr Zaporozhets and published by CRC Press. This book was released on 2011-05-13 with total page 435 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aircraft noise has adverse impacts on passengers, airport staff and people living near airports, it thus limits the capacity of regional and international airports throughout the world. Reducing perceived noise of aircraft involves reduction of noise at source, along the propagation path and at the receiver. Effective noise control demands highly skilled and knowledgeable engineers. This book is for them. It shows you how accurate and reliable information about aircraft noise levels can be gained by calculations using appropriate generation and propagation models, or by measurements with effective monitoring systems. It also explains how to allow for atmospheric conditions, natural and artificial topography as well as detailing necessary measurement techniques.
Download or read book Conceptual Aircraft Design written by Ajoy Kumar Kundu and published by John Wiley & Sons. This book was released on 2019-04-08 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a Comprehensive Introduction to Aircraft Design with an Industrial Approach This book introduces readers to aircraft design, placing great emphasis on industrial practice. It includes worked out design examples for several different classes of aircraft, including Learjet 45, Tucano Turboprop Trainer, BAe Hawk and Airbus A320. It considers performance substantiation and compliance to certification requirements and market specifications of take-off/landing field lengths, initial climb/high speed cruise, turning capability and payload/range. Military requirements are discussed, covering some aspects of combat, as is operating cost estimation methodology, safety considerations, environmental issues, flight deck layout, avionics and more general aircraft systems. The book also includes a chapter on electric aircraft design along with a full range of industry standard aircraft sizing analyses. Split into two parts, Conceptual Aircraft Design: An Industrial Approach spends the first part dealing with the pre-requisite information for configuring aircraft so that readers can make informed decisions when designing vessels. The second part devotes itself to new aircraft concept definition. It also offers additional analyses and design information (e.g., on cost, manufacture, systems, role of CFD, etc.) integral to conceptual design study. The book finishes with an introduction to electric aircraft and futuristic design concepts currently under study. Presents an informative, industrial approach to aircraft design Features design examples for aircraft such as the Learjet 45, Tucano Turboprop Trainer, BAe Hawk, Airbus A320 Includes a full range of industry standard aircraft sizing analyses Looks at several performance substantiation and compliance to certification requirements Discusses the military requirements covering some combat aspects Accompanied by a website hosting supporting material Conceptual Aircraft Design: An Industrial Approach is an excellent resource for those designing and building modern aircraft for commercial, military, and private use.
