Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Simulation Of Supersonic Jet Noise Reduction Using Fluid Inserts For Low Bypass Ratio Turbofans
Download Simulation Of Supersonic Jet Noise Reduction Using Fluid Inserts For Low Bypass Ratio Turbofans full books in PDF, epub, and Kindle. Read online Simulation Of Supersonic Jet Noise Reduction Using Fluid Inserts For Low Bypass Ratio Turbofans ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Simulation of Supersonic Jet Noise Reduction Using Fluid Inserts for Low Bypass Ratio Turbofans by : Chitrarth Prasad
Download or read book Simulation of Supersonic Jet Noise Reduction Using Fluid Inserts for Low Bypass Ratio Turbofans written by Chitrarth Prasad and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The design constraints on jet engines for high performance supersonic military aircraft require lower bypass ratios and supersonic exhaust velocities, which result in very high noise levels. This is a great concern to the US Navy as the noise generated from the jet exhaust of high performance supersonic military aircraft can affect the hearing and performance of personnel working in close proximity of the aircraft. There have been reports about the US Department of Veteran Affairs spending over hundreds of millions of dollars in disability payments for hearing loss compensation to former Navy personnel. In addition to this, jet noise is also a source of annoyance in communities in the vicinity of airbases and military training routes.Over the years, several noise reduction methods have been proposed with varying levels of success. The most effective noise reduction strategies include the installation of chevrons, and the use of corrugated seals, among many others. One primary disadvantage of these technologies is that they are passive technologies and cannot be switched off or modified after take-off and hence may reduce overall aircraft performance. An active, though steady, noise reduction technology is the use of fluid inserts in the divergent section of a converging-diverging nozzle. The fluid inserts consist of rows of injectors that inject a small amount of bypass air into the diverging section of the nozzle. It has been shown that by altering the configuration and operating conditions of the fluid inserts, noise reduction for both mixing and shock noise can be achieved. Since this blowing can be controlled, the fluid inserts can be switched off or modified after take-off to minimize any performance penalty to the aircraft.Although considerable experimental research has been performed to explore the effects of fluid inserts on the jet exhaust, the available data have been found to be insufficient to correlate the noise reduction with changes in the flow-field due to the noise reduction device. The present study is an extension to the previousresearch on fluid inserts that uses Large Eddy Simulation (LES) with the Ffowcs Williams-Hawkings (FWH) analogy for farfield noise prediction. The simulations are carried out using a commercially available CFD package, STAR-CCM+. The project aims to simulate and analyze the unsteady flow changes associated withthe noise reduction device to help understand the detailed mechanisms for the observed noise reductions.Different fluid insert configurations are used to analyze the effect of individual injector placement in a fluid insert on noise generation. It is observed that the changes in upstream noise correlate extremely well with the shock structure of the fluid insert jets downstream of the nozzle exit. Further insight into the noisereduction patterns is obtained by using two-point space time correlations and the use of the modal techniques such as Proper Orthogonal Decomposition on the near-field data on the FWH surface, which show that fluid inserts reduce the amplitude of the noise radiating coherent structures. Using Doaks Momentum Potential Theory, it is observed that the changes associated with fluid insertson the hydrodynamic and acoustic modes correlate well with the far-field noise reduction.
Book Synopsis Simulations of the Flow Generated by Fluidic Inserts for Supersonic Jet Noise Reduction Based on Steady RANS Simulations by : Matthew Kapusta
Download or read book Simulations of the Flow Generated by Fluidic Inserts for Supersonic Jet Noise Reduction Based on Steady RANS Simulations written by Matthew Kapusta and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The investigation of military jet noise prediction and reduction is an ongoing activity. Supersonic military jets radiate higher noise levels than commercial aircraft and are not subject to noise requirements. The noise generating mechanisms for high-speed jets are not entirely understood, making it difficult to set strict noise standards similar to those imposed for commercial aircraft. However, many noise reduction techniques have been applied to attempt to alleviate environmental and health concerns. Little success has been achieved to date for noise reduction of exhaust jets on supersonic tactical aircraft.A newly developed method involves a system that generates fluidic inserts in a supersonic nozzle flow to produce noise reduction. Numerical simulations have been performed for a military-style basline nozzle and with the noise reduction method of fluidic inserts used at a design Mach number of 1.65 and at various off design conditions. The purpose of the current numerical study is to provide insight for the flow field generated by the fluidic inserts used to reduce supersonic jet noise. The supersonic jet simulations are based on the use of high fidelity meshes combined with advanced CFD technology. Steady Reynolds-averaged Navier-Stokes (RANS) simulations are used to predict the flow field. Noise measurements have been performed experimentally and the results from the numerical simulations provide a correlation between aerodynamic properties and the corresponding noise reduction. The complex nozzle geometry is modeled using both an unstructured mesh and a multiblock structured mesh. The grids are generated by ANSYS ICEM and Gridgen respectively. The numerical simulations are performed using ANSYS CFX and Wind-US. The simulations with Wind-US use the Spalart-Allmaras turbulence model, while the simulations with ANSYS CFX use the Menter SST turbulence model. The results from the two flow solvers are compared and provide good agreement. The objective is to simulate a military-style nozzle, which resembles engines of the GE F404 family, with fluidic inserts. The purpose of the fluidic inserts is to alter the flow field similar to that of a hard wall corrugation in order to reduce components of noise radiation. The addition of the fluidic inserts increases the complexity of the flow field for the supersonic jet. The numerical simulations performed help to better distinguish the effects on the flow field due to the fluidic inserts. Preliminary work has been performed on a simpler geometry to provide further insight to the effect of the fluidic inserts on the supersonic jet flow field. These simulations are performed by fluid injection into a supersonic freestream over a flat plate. All numerical simulations used a freestream Mach number of 1.5. The numerical simulations used a wide range of pressure ratios for injecting the fluid into the supersonic freestream. By changing the pressure ratio of the fluid injection, the deflection of the freestream flow was better understood. Simulations on a full three dimensional nozzle with fluidic inserts were performed with conditions based on the preliminary studies. Parameters such as total pressure and total temperature provide a representation of the fluidic insert shape. Other integrated flow properties at the nozzle exit such as streamwise vorticity and pressure differential were used to correlate with the noise reduction seen in the experiments.
Book Synopsis Experimental Investigation of the Noise Reduction of Supersonic Exhaust Jets with Fluidic Inserts by : Russell Powers
Download or read book Experimental Investigation of the Noise Reduction of Supersonic Exhaust Jets with Fluidic Inserts written by Russell Powers and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The noise produced by the supersonic, high temperature jets that exhaust from military aircraft is becoming a hazard to naval personnel and a disturbance to communities near military bases. Methods to reduce the noise produced from these jets in a practical full-scale environment are difficult. The development and analysis of distributed nozzle blowing for the reduction of radiated noise from supersonic jets is described. Model scale experiments of jets that simulate the exhaust jets from typical low-bypass ratio military jet aircraft engines during takeoff are performed. Fluidic inserts are created that use distributed blowing in the divergent section of the nozzle to simulate mechanical, hardwall corrugations, while having the advantage of being an active control method. This research focuses on model scale experiments to better understand the fluidic insert noise reduction method. Distributed blowing within the divergent section of the military-style convergent divergent nozzle alters the shock structure of the jet in addition to creating streamwise vorticity for the reduction of mixing noise. Enhancements to the fluidic insert design have been performed along with experiments over a large number of injection parameters and core jet conditions. Primarily military-style round nozzles have been used, with preliminary measurements of hardwall corrugations and fluidic inserts in rectangular nozzle geometries also performed. It has been shown that the noise reduction of the fluidic inserts is most heavily dependent upon the momentum flux ratio between the injector and core jet. Maximum reductions of approximately 5.5 dB OASPL have been observed with practical mass flow rates and injection pressures. The first measurements with fluidic inserts in the presence of a forward flight stream have been performed. Optimal noise reduction occurs at similar injector parameters in the presence of forward flight. Fluidic inserts in the presence of a forward flight stream were observed to reduce the peak mixing noise below the already reduced levels by nearly 4 dB OASPL and the broadband shock-associated noise by nearly 3 dB OASPL. Unsteady velocity measurements are used to complement acoustic results of jets with fluidic inserts. Measured axial turbulence intensities and mean axial velocity are examined to illuminate the differences in the flow field from jets with fluidic inserts. Comparisons of laser Doppler measurements with RANS CFD simulations are shown with good agreement. Analysis of the effect of spatial turbulence on the measured quantities is performed. Experimental model scale measurements of jets with and without fluidic inserts over a simulated carrier deck are presented. The model carrier environment consists of a ground plane of adjustable distance below the jet, and a simulated jet blast deflector similar to those found in practice. Measurements are performed with far-field microphones, near-field microphones, and unsteady pressure sensors. The constructive and destructive interference that results from the interaction of the direct and reflected sound waves is observed and compared with results from free jets. The noise reduction of fluidic inserts in a realistic carrier deck environment with steering of the ``quiet planes'' is examined. The overall sound pressure level in heat-simulated jets is reduced by 3-5 dB depending on the specific angle and ground plane height. Jets impinging upon a modeled jet blast deflector are tested in addition to jets solely in the presence of the carrier deck. Observed modifications to the acoustic field from the presence of the jet blast deflector include downstream acoustic shielding and low frequency augmentation. The region of maximum noise radiation for heat-simulated jets from nozzles with fluidic inserts impinging on the jet blast deflector is reduced in overall sound pressure level by 4-7 dB. This region includes areas where aircraft carrier personnel are located.
Book Synopsis Pressure Measurements in a Supersonic Jet with Fluid Inserts by : James Falcone
Download or read book Pressure Measurements in a Supersonic Jet with Fluid Inserts written by James Falcone and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Extremely high levels of noise, capable of damaging the human ear, are emitted from theexhaust leaving military grade aircraft engines. Military personnel, specifically those on the decksof aircraft carriers, are regularly exposed to this dangerous noise and as a result often sustainpermanent hearing damage. A novel approach to reducing the noise levels experienced by thesepersonnel is through the use of fluid inserts in the diverging section of an aircraft engines nozzle.These fluid inserts blow additional air into the exhaust flow which has been shown to effectivelyreduce noise. This study sought to further the understanding of the flow physics by which thefluid inserts can reduce noise. Pressure surveys of a scaled GE 404 class engine nozzle werecompleted with and without the use of fluid inserts. The alterations created by the fluid inserts inthe downstream flow are visualized and discussed. The experimental results are also compared toRANS CFD simulations of jets from the same nozzle and operating conditions to further evaluatethe computations and improve future simulations.Throughout the duration of the experiments, jet asymmetries were also carefully explored forthe baseline jet as well as the fluid insert jet. Asymmetries within a jet can have an impact onnoise reduction by unknowingly redistributing the flow in undesirable ways. The reasons for theseasymmetries are proposed.
Book Synopsis An Analysis of Noise Reduction in Supersonic Jets by Fluid Insert Nozzles by : Venkata Rajeshwar Majety
Download or read book An Analysis of Noise Reduction in Supersonic Jets by Fluid Insert Nozzles written by Venkata Rajeshwar Majety and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary objective of this research is to analyze the noise reduction obtained with the use of fluid insert nozzles in heated supersonic jets. In this regard, the far-field pressure data of two types of nozzles (baseline and fluid inserts) are used to investigate and validate the spatiotemporal characteristics of the radiation field, and to determine the sound reduction obtained. Further, to gain a better understanding of the noise radiated, the polar correlation technique is used to determine the location and relative strengths of the noise sources. The results of this research can be summarized as follows: the fluid insert nozzles reduce the overall sound radiated by a maximum amount of 10 dB and 4 dB respectively in the downstream and upstream directions of the jet flow. The highest levels of sound are radiated in the downstream directions of the jet flow for all the nozzle cases. The greatest amount of noise reduction is obtained in the 60 azimuthal plane. Irrespective of the nozzle type, significant noise source strength is located within ten nozzle diameters downstream from the nozzle exit. As the frequency increases, the highest peak of the noise source strength distribution moves closer to the nozzle exit.
Book Synopsis A Fluid/acoustic Coupled Simulation of Supersonic Jet Noise by : K. Viswanathan
Download or read book A Fluid/acoustic Coupled Simulation of Supersonic Jet Noise written by K. Viswanathan and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721276707 Total Pages :26 pages Book Rating :4.2/5 (767 download)
Book Synopsis Simulation of Supersonic Jet Noise with the Adaptation of Overflow Cfd Code and Kirchhoff Surface Integral by : National Aeronautics and Space Administration (NASA)
Download or read book Simulation of Supersonic Jet Noise with the Adaptation of Overflow Cfd Code and Kirchhoff Surface Integral written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-19 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow field are modeled with the aid of Spalart-Allmaras one-equation turbulence model. Appropriate acoustic and outflow boundary conditions were implemented to compute time-dependent acoustic pressure in the nonlinear source-field. Based on the specification of acoustic pressure, its temporal and normal derivatives on the Kirchhoff surface, the near-field and the far-field sound pressure levels are computed via Kirchhoff surface integral, with the Kirchhoff surface chosen to enclose the nonlinear sound source region described by the CFD code. The methods are validated by a comparison of the predictions of sound pressure levels with the available data for an axisymmetric turbulent supersonic (Mach 2) perfectly expanded jet. Kandula, Max and Caimi, Raoul and Steinrock, T. (Technical Monitor) Kennedy Space Center NASA/TM-2001-210263, NAS 1.15:210263
Book Synopsis Flinovia—Flow Induced Noise and Vibration Issues and Aspects-II by : Elena Ciappi
Download or read book Flinovia—Flow Induced Noise and Vibration Issues and Aspects-II written by Elena Ciappi and published by Springer. This book was released on 2018-05-25 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the proceedings of the Second International Workshop on Flow Induced Noise and Vibration (FLINOVIA), which was held in Penn State, USA, in April 2016. The authors’ backgrounds represent a mix of academia, government, and industry, and several papers include applications to important problems for underwater vehicles, aerospace structures and commercial transportation. The book offers a valuable reference guide for all those working in the area of flow-induced vibration and noise. Flow induced vibration and noise (FIVN) remains a critical research topic. Even after over 50 years of intensive research, accurate and cost-effective FIVN simulation and measurement techniques remain elusive. This book gathers the latest research from some of the most prominent experts in the field. The book describes methods for characterizing wall pressure fluctuations, including subsonic and supersonic turbulent boundary layer flows over smooth and rough surfaces using computational methods like Large Eddy Simulation; for inferring wall pressure fluctuations using inverse techniques based on panel vibrations or holographic pressure sensor arrays; for calculating the resulting structural vibrations and radiated sound using traditional finite element methods, as well as advanced methods like Energy Finite Elements; for using scaling approaches to universally collapse flow-excited vibration and noise spectra; and for computing time histories of structural response, including alternating stresses.
Book Synopsis Simulation of Supersonic Jet Noise with the Adaptation of Overflow Cfd Code and Kirchhoff Surface Integral by : Max Kandula
Download or read book Simulation of Supersonic Jet Noise with the Adaptation of Overflow Cfd Code and Kirchhoff Surface Integral written by Max Kandula and published by BiblioGov. This book was released on 2013-08 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow field are modeled with the aid of Spalart-Allmaras one-equation turbulence model. Appropriate acoustic and outflow boundary conditions were implemented to compute time-dependent acoustic pressure in the nonlinear source-field. Based on the specification of acoustic pressure, its temporal and normal derivatives on the Kirchhoff surface, the near-field and the far-field sound pressure levels are computed via Kirchhoff surface integral, with the Kirchhoff surface chosen to enclose the nonlinear sound source region described by the CFD code. The methods are validated by a comparison of the predictions of sound pressure levels with the available data for an axisymmetric turbulent supersonic (Mach 2) perfectly expanded jet.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1987 with total page 1126 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Book Synopsis Supression of Jet Noise with Emphasis on the Near Field by : Kenneth M. Eldred
Download or read book Supression of Jet Noise with Emphasis on the Near Field written by Kenneth M. Eldred and published by . This book was released on 1963 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721981823 Total Pages :360 pages Book Rating :4.9/5 (818 download)
Book Synopsis Advanced Subsonic Technology (Ast) Separate-Flow High-Bypass Ratio Nozzle Noise Reduction Program Test Report by : National Aeronautics and Space Administration (NASA)
Download or read book Advanced Subsonic Technology (Ast) Separate-Flow High-Bypass Ratio Nozzle Noise Reduction Program Test Report written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-20 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: NASA s model-scale nozzle noise tests show that it is possible to achieve a 3 EPNdB jet noise reduction with inwardfacing chevrons and flipper-tabs installed on the primary nozzle and fan nozzle chevrons. These chevrons and tabs are simple devices and are easy to be incorporated into existing short duct separate-flow nonmixed nozzle exhaust systems. However, these devices are expected to cause some small amount of thrust loss relative to the axisymmetric baseline nozzle system. Thus, it is important to have these devices further tested in a calibrated nozzle performance test facility to quantify the thrust performances of these devices. The choice of chevrons or tabs for jet noise suppression would most likely be based on the results of thrust loss performance tests to be conducted by Aero System Engineering (ASE) Inc. It is anticipated that the most promising concepts identified from this program will be validated in full scale engine tests at both Pratt & Whitney and Allied-Signal, under funding from NASA s Engine Validation of Noise Reduction Concepts (EVNRC) programs. This will bring the technology readiness level to the point where the jet noise suppression concepts could be incorporated with high confidence into either new or existing turbofan engines having short-duct, separate-flow nacelles. Low, John K. C. and Schweiger, Paul S. and Premo, John W. and Barber, Thomas J. and Saiyed, Naseem (Technical Monitor) Glenn Research Center NAS3-27727; WU 522-81-11...
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 :United States. National Aeronautics and Space Administration. Scientific and Technical Information Office Publisher : ISBN 13 : Total Pages :356 pages Book Rating :4.:/5 (31 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:
Book Synopsis The Reduction of Supersonic Jet Noise Using Pulsed Microjet Injection by : Paul Aaron Ragaller
Download or read book The Reduction of Supersonic Jet Noise Using Pulsed Microjet Injection written by Paul Aaron Ragaller and published by . This book was released on 2007 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is concerned with the active control of supersonic jet noise using pulsed microjet injection at the nozzle exit. Experimental investigations were carried out using this control method on an ideally expanded Mach 1.8 jet operating at 900, 1300 and 1700'F. Six Bosch fuel injectors were modified and mounted on a toroidal manifold around a Mach 1.8 nozzle. Noise data were collected from the jet at baseline condition, which refers to the uncontrolled case. The injectors were fired at pressures of 400 and 800 psig, using water, at frequencies of 1, 5 and 10 Hz and at duty cycles of 50 and 75%. For comparison, acoustic data were also collected from the jet while the microjets were injecting steadily at a constant pressure. The results led to the following two conclusions: for injection at a given mass flow rate, noise reductions are higher with pulsed injection compared to the steady case, and for injection at a given pressure, the amount of noise reduction increases with duty cycle. In particular, for pulsing at a 50% duty cycle, pulsing achieves comparable noise reduction as compared to steady injection at all of the temperatures tested while using only 66% of the mass flow rate. The most dramatic result was achieved at 17000F for pulsing at a 75% duty cycle with an injection pressure of 800 psig. In this case, pulsing achieves 317% of the noise reduction as compared to steady injection (corresponding to 2.6 and 0.8 dB respectively) while using a comparable amount of water. Similar results were obtained at lower temperatures as well. At all operating points it was found that less water is used with pulsing to achieve a given noise reduction, and is realized at the cost of a higher injection pressure. Suggestions are provided as to how to determine the frequency and duty cycle required for maximum noise suppression with the least amount of water.
Book Synopsis Jet Noise Reduction Potential from Emerging Variable Cycle Technologies by : Brenda Henderson
Download or read book Jet Noise Reduction Potential from Emerging Variable Cycle Technologies written by Brenda Henderson and published by BiblioGov. This book was released on 2013-06 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic and flow-field experiments were conducted on exhaust concepts for the next generation supersonic, commercial aircraft. The concepts were developed by Lockheed Martin (LM), Rolls-Royce Liberty Works (RRLW), and General Electric Global Research (GEGR) as part of an N+2 (next generation forward) aircraft system study initiated by the Supersonics Project in NASA s Fundamental Aeronautics Program. The experiments were conducted in the Aero-Acoustic Propulsion Laboratory at the NASA Glenn Research Center. The exhaust concepts utilized ejectors, inverted velocity profiles, and fluidic shields. One of the ejector concepts was found to produce stagnant flow within the ejector and the other ejector concept produced discrete-frequency tones that degraded the acoustic performance of the model. The concept incorporating an inverted velocity profile and fluid shield produced overall-sound-pressure-level reductions of 6 dB relative to a single stream nozzle at the peak jet noise angle for some nozzle pressure ratios. Flow separations in the nozzle degraded the acoustic performance of the inverted velocity profile model at low nozzle pressure ratios.
Book Synopsis Aeroacoustics of Supersonic Jet Interacting with Solid Surfaces and Its Suppression by : Seyyed Saman Salehian
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.
