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Acoustic Efficiency Of Azimuthal Modes In Jet Noise Using Chevron Nozzles
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Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721832385 Total Pages :36 pages Book Rating :4.8/5 (323 download)
Book Synopsis Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles by : National Aeronautics and Space Administration (NASA)
Download or read book Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-24 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The link between azimuthal modes in jet turbulence and in the acoustic sound field has been examined in cold, round jets. Chevron nozzles, however, impart an azimuthal structure on the jet with a shape dependent on the number, length and penetration angle of the chevrons. Two particular chevron nozzles, with 3 and 4 primary chevrons respectively, and a round baseline nozzle are compared at both cold and hot jet conditions to determine how chevrons impact the modal structure of the flow and how that change relates to the sound field. The results show that, although the chevrons have a large impact on the azimuthal shape of the mean axial velocity, the impact of chevrons on the azimuthal structure of the fluctuating axial velocity is small at the cold jet condition and smaller still at the hot jet condition. This is supported by results in the azimuthal structure of the sound field, which also shows little difference in between the two chevron nozzles and the baseline nozzle in the distribution of energy across the azimuthal modes measured. Brown, Clifford A. and Bridges, James Glenn Research Center NASA/TM-2006-214364, E-15640, AIAA Paper 2006-2654
Book Synopsis Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles by : Clifford A. Brown
Download or read book Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles written by Clifford A. Brown and published by . This book was released on 2006 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles by : Nasa Technical Reports Server (Ntrs)
Download or read book Acoustic Efficiency of Azimuthal Modes in Jet Noise Using Chevron Nozzles written by Nasa Technical Reports Server (Ntrs) and published by BiblioGov. This book was released on 2013-07 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The link between azimuthal modes in jet turbulence and in the acoustic sound field has been examined in cold, round jets. Chevron nozzles, however, impart an azimuthal structure on the jet with a shape dependent on the number, length and penetration angle of the chevrons. Two particular chevron nozzles, with 3 and 4 primary chevrons respectively, and a round baseline nozzle are compared at both cold and hot jet conditions to determine how chevrons impact the modal structure of the flow and how that change relates to the sound field. The results show that, although the chevrons have a large impact on the azimuthal shape of the mean axial velocity, the impact of chevrons on the azimuthal structure of the fluctuating axial velocity is small at the cold jet condition and smaller still at the hot jet condition. This is supported by results in the azimuthal structure of the sound field, which also shows little difference in between the two chevron nozzles and the baseline nozzle in the distribution of energy across the azimuthal modes measured.
Book Synopsis Control of Jet Noise Through Mixing Enhancement by :
Download or read book Control of Jet Noise Through Mixing Enhancement written by and published by . This book was released on 2003 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Recent Advances in Aerospace Engineering by : Sanjay Singh
Download or read book Recent Advances in Aerospace Engineering written by Sanjay Singh and published by Springer Nature. This book was released on with total page 605 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fluid Mechanics and Fluid Power (Vol. 1) by : Suvanjan Bhattacharyya
Download or read book Fluid Mechanics and Fluid Power (Vol. 1) written by Suvanjan Bhattacharyya and published by Springer Nature. This book was released on 2023-05-10 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the select proceedings of the 48th National Conference on Fluid Mechanics and Fluid Power (FMFP 2021) held at BITS Pilani in December 2021. It covers the topics such as fluid mechanics, measurement techniques in fluid flows, computational fluid dynamics, instability, transition and turbulence, fluid‐structure interaction, multiphase flows, micro- and nanoscale transport, bio-fluid mechanics, aerodynamics, turbomachinery, propulsion and power. The book will be useful for researchers and professionals interested in the broad field of mechanics.
Book Synopsis Active Control of High Speed Jets for Noise Mitigation by : Amy Eileen McCluskey
Download or read book Active Control of High Speed Jets for Noise Mitigation written by Amy Eileen McCluskey and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Research, design, and experimentation were performed in the Gas Dynamics and Turbulence Laboratory at The Ohio State University to control far-field noise for high-speed jets and observe the effects of control with the purpose of noise mitigation. Recently localized arc filament plasma actuators (LAFPA) were developed to force an axisymmetric Mach 0.9 jet. Previous experimentation was improved upon by adding four actuators to an eight actuator equally spaced setup. A new nozzle extension was designed to house these twelve actuators and an adaptor was developed to provide flush mounting of the electrodes of the actuators between the nozzle and extension. The twelve actuators were used to excite the flow over a large frequency range, which was expressed in terms of the non-dimension forcing Strouhal number (StDF). Microphones, mounted at angles of 30° and 90°, were used to collect far-field sound pressure levels. The response of the jet varied greatly with azimuthal mode and StDF. The perturbations were observed to greatly affect the far-field sound pressure levels at StDF's between 0.1 and 5. Furthermore, greater noise mitigation was recorded at higher modes such as azimuthal modes 5 and "6. This was contrasted to the enhanced mixing observed at lower modes such as m = 1 or "1. However, the effects of actuation on the flow were independent of azimuthal mode when forced at a StD higher than about 2. While these patterns and results were observed at an angle of 30° to the jet axis, the effects remained unclear at an angle of 90°. However, the general observation was made that forcing at higher modes significantly reduces far-field noise.
Book Synopsis Ground and In-flight Acoustic and Performance Characteristics of Jet-aircraft Exhaust Noise Supressors by : Willard D. Coles
Download or read book Ground and In-flight Acoustic and Performance Characteristics of Jet-aircraft Exhaust Noise Supressors written by Willard D. Coles and published by . This book was released on 1961 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aerospace America written by and published by . This book was released on 2006 with total page 732 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis AIAA Journal by : American Institute of Aeronautics and Astronautics
Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2008 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Multiple-nozzle Geometry on Jet Noise Generation by : Vern G. Rollin
Download or read book Effect of Multiple-nozzle Geometry on Jet Noise Generation written by Vern G. Rollin and published by . This book was released on 1961 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Use of Acoustic Scale Models for Investigating Near Field Noise of Jet and Rocket Engines by : Walter V. Morgan
Download or read book The Use of Acoustic Scale Models for Investigating Near Field Noise of Jet and Rocket Engines written by Walter V. Morgan and published by . This book was released on 1961 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Simulated Flight Acoustic Investigation of Treated Ejector Effectiveness on Advanced Mechanical Suppressors for High Velocity Jet Noise Reduction by : J. F. Brausch
Download or read book Simulated Flight Acoustic Investigation of Treated Ejector Effectiveness on Advanced Mechanical Suppressors for High Velocity Jet Noise Reduction written by J. F. Brausch and published by . This book was released on 1986 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Optimization and Modeling of Noise Reduction for Turbulent Jets with Induced Asymmetry by : Sara Rostamimonjezi
Download or read book Optimization and Modeling of Noise Reduction for Turbulent Jets with Induced Asymmetry written by Sara Rostamimonjezi and published by . This book was released on 2013 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project relates to the development of next-generation high-speed aircraft that are efficient and environmentally compliant. The emphasis of the research is on reducing noise from high-performance engines that will power these aircraft. A strong component of engine noise is jet mixing noise that comes from the turbulent mixing process between the high-speed exhaust flow of the engine and the atmosphere. The fan flow deflection method (FFD) suppresses jet noise by deflecting the fan stream downward, by a few degrees, with respect to the core stream. This reduces the convective Mach number of the primary shear layer and turbulent kinetic energy in the downward direction and therefore reduces the noise emitted towards the ground. The redistribution of the fan stream is achieved with inserting airfoil-shaped vanes inside the fan duct. Aerodynamic optimization of FFD has been done by Dr. Juntao Xiong using a computational fluid dynamics code to maximize reduction of noise perceived by the community while minimizing aerodynamic losses. The optimal vane airfoils are used in a parametric experimental study of 50 4-vane deflector configurations. The vane chord length, angle of attack, and azimuthal location are the parameters studied in acoustic optimization. The best vane configuration yields a reduction in cumulative (downward + sideline) effective perceived noise level (EPNL) of 5.3 dB. The optimization study underscores the sensitivity of FFD to deflector parameters and the need for careful design in the practical implementation of this noise reduction approach. An analytical model based on Reynolds Averaged Navier Stokes (RANS) and acoustic analogy is developed to predict the spectral changes from a known baseline in the direction of peak emission. A generalized form for space-time correlation is introduced that allows shapes beyond the traditional exponential forms. Azimuthal directivity based on the wavepacket model of jet noise is integrated with the acoustic analogy model. A physics-based definition of convective Mach number is proposed. The predicted noise reduction is in reasonable agreement with the experiments. The study underscores the importance of a proper definition of convective Mach number when modeling noise in the direction of peak emission.
Book Synopsis An Investigation of Innovative Technologies for Reduction of Jet Noise in Medium and High Bypass Turbofan Engines by :
Download or read book An Investigation of Innovative Technologies for Reduction of Jet Noise in Medium and High Bypass Turbofan Engines written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This research project has developed a new, large-scale, nozzle acoustic test rig capable of simulating the exhaust flows of separate flow exhaust systems in medium and high bypass turbofan engines. This rig has subsequently been used to advance the understanding of two state-of-the-art jet noise reduction technologies. The first technology investigated is an emerging jet noise reduction technology known as chevron nozzles. The fundamental goal of this investigation was to advance the understanding of the fundamental physical mechanisms responsible for the acoustic benefits provided by these nozzles. Additionally, this study sought to establish the relationship between these physical mechanisms and the chevron geometric parameters. A comprehensive set of data was collected, including far-field and near-field acoustic data as well as flow field measurements. In addition to illustrating the ability of the chevron nozzles to provide acoustic benefits in important aircraft certification metrics such as effective perceived noise level (EPNL), this investigation successfully identified two of the fundamental physical mechanisms responsible for this reduction. The flow field measurements showed the chevron to redistribute energy between the core and fan streams to effectively reduce low frequency noise by reducing the length of the jet potential core. However, this redistribution of energy produced increases in turbulent kinetic energy of up to 45% leading to a degradation of the chevron benefit at higher frequencies ... plane to reduce jet noise. The principal advantage of such an approach is that it is an active technology that can be activated as needed and, as such, may be more acceptable in aircraft engines from a performance standpoint than passive technologies. This study successfully demonstrated the feasibility of this technology by showing that effective jet noise reduction can be provided in a broad range of flow conditions using less than 1% of the mean jet mass flow. An investigation of injection geometric parameters identified the injection pitch angle as the most influential parameter with respect to jet noise reduction. Furthermore, an investigation of scaling effects showed a momentum ratio of approximately 1.5% to provide reductions in sound pressure level between 1 and 2 dB across a wide range of frequencies for a wide range of flow conditions and scales including both single stream and dual stream flows. PIV flow field measurements identified the fundamental physical mechanism of the noise reduction to be a near uniform reduction in shear layer turbulence.
Author :American Society of Mechanical Engineers. Fluids Engineering Division Publisher : ISBN 13 : Total Pages :1092 pages Book Rating :4.E/5 ( download)
Book Synopsis Proceedings of the ASME Fluids Engineering Division Summer Conference, 2006: Forums by : American Society of Mechanical Engineers. Fluids Engineering Division
Download or read book Proceedings of the ASME Fluids Engineering Division Summer Conference, 2006: Forums written by American Society of Mechanical Engineers. Fluids Engineering Division and published by . This book was released on 2006 with total page 1092 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :United States. National Aeronautics and Space Administration. Scientific and Technical Information Office Publisher : ISBN 13 : Total Pages :356 pages Book Rating :4.:/5 (317 download)
Book Synopsis Acoustic Tests of Duct-burning Turbofan Jet Noise Simulation by : United States. National Aeronautics and Space Administration. Scientific and Technical Information Office
Download or read book Acoustic Tests of Duct-burning Turbofan Jet Noise Simulation written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Office and published by . This book was released on 1978 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of a static acoustic and aerodynamic performance, model-scale test program on coannular unsuppressed and multielement fan suppressed nozzle configurations are summarized. The results of the static acoustic tests show a very beneficial interaction effect. When the measured noise levels were compared with the predicted noise levels of two independent but equivalent conical nozzle flow streams, noise reductions for the unsuppressed coannular nozzles were of the order of 10 PNdB; high levels of suppression (8 PNdB) were still maintained even when only a small amount of core stream flow was used. The multielement fan suppressed coannular nozzle tests showed 15 PNdB noise reductions and up to 18 PNdB noise reductions when a treated ejector was added. The static aerodynamic performance tests showed that the unsuppressed coannular plug nozzles obtained gross thrust coefficients of 0.972, with 1.2 to 1.7 percent lower levels for the multielement fan-suppressed coannular flow nozzles. For the first time anywhere, laser velocimeter velocity profile measurements were made on these types of nozzle configurations and with supersonic heated flow conditions. Measurements showed that a very rapid decay in the mean velocity occurs for the nozzle tested.
