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Supersonic Jet Shock Noise Reduction
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Book Synopsis Supersonic Jet Shock Noise Reduction by :
Download or read book Supersonic Jet Shock Noise Reduction written by and published by . This book was released on 1984 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Generation and Radiation of Supersonic Jet Noise: Future studies for definition of supersonic jet noise generation and reduction mechanisms by :
Download or read book The Generation and Radiation of Supersonic Jet Noise: Future studies for definition of supersonic jet noise generation and reduction mechanisms written by and published by . This book was released on 1972 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 The Generation and Radiation of Supersonic Jet Noise: Append. 2. Shock associated noise data by :
Download or read book The Generation and Radiation of Supersonic Jet Noise: Append. 2. Shock associated noise data written by and published by . This book was released on 1972 with total page 694 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Analysis of Supersonic Jet Noise Reduction Concepts by : C. Kannepalli
Download or read book Analysis of Supersonic Jet Noise Reduction Concepts written by C. Kannepalli and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets by : Nicholas S. Heeb
Download or read book Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets written by Nicholas S. Heeb and published by . This book was released on 2015 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation into the effect of azimuthal variance of chevrons and fluidically enhanced chevrons applied to supersonic jets is presented. Flow field measurements of streamwise and cross-stream particle imaging velocimetry were employed to determine the causes of noise reduction, which was demonstrated through acoustic measurements. Results were obtained in the over- and under- expanded regimes, and at the design condition, though emphasis was placed on the overexpanded regime due to practical application. Surveys of chevron geometry, number, and arrangement were undertaken in an effort to reduce noise and/or incurred performance penalties. Penetration was found to be positively correlated with noise reduction in the overexpanded regime, and negatively correlated in underexpanded operation due to increased effective penetration and high frequency penalty, respectively. The effect of arrangement indicated the beveled configuration achieved optimal abatement in the ideally and underexpanded regimes due to superior BSAN reduction. The symmetric configuration achieved optimal overexpanded noise reduction due to LSS suppression from improved vortex persistence. Increases in chevron number generally improved reduction of all noise components for lower penetration configurations. Higher penetration configurations reached levels of saturation in the four chevron range, with the potential to introduce secondary shock structures and generate additional noise with higher number. Alternation of penetration generated limited benefit, with slight reduction of the high frequency penalty caused by increased shock spacing. The combination of alternating penetration with beveled and clustered configurations achieved comparable noise reduction to the standard counterparts. Analysis of the entire data set indicated initial improvements with projected area that saturated after a given level and either plateaued or degraded with additional increases. Optimal reductions were 3-7dB depending on operating condition and observation angle. The fluidic enhancement of the low penetration chevrons indicated significant improvement in the overexpanded regime, with detrimental effect at higher conditions. Improvements were generally due to shock noise and turbulent mixing noise reductions caused by decreased shock strength and LSS growth inhibition. Investigation of azimuthal configurations indicated further improvements were achieved by the clustered configuration due to additional BSAN reductions caused by drastic modification of the shock cell structure due to elliptification of the jet cross section.
Book Synopsis Fundamental Study of Jet Noise Generation and Suppression by : W. C. Sperry
Download or read book Fundamental Study of Jet Noise Generation and Suppression written by W. C. Sperry and published by . This book was released on 1960 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Initial Results of a Porous Plug Nozzle for Supersonic Jet Noise Suppression by :
Download or read book Initial Results of a Porous Plug Nozzle for Supersonic Jet Noise Suppression written by and published by . This book was released on 1978 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Supersonic Jet Noise Reduction and Mixing Enhancement Through Nozzle Trailing Edge Modifications by : Mo Samimy
Download or read book Supersonic Jet Noise Reduction and Mixing Enhancement Through Nozzle Trailing Edge Modifications written by Mo Samimy and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Generation and Radiation of Supersonic Jet Noise: Summary of supersonic jet noise studies by :
Download or read book The Generation and Radiation of Supersonic Jet Noise: Summary of supersonic jet noise studies written by and published by . This book was released on 1972 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Supersonic Jet Noise Reduction by a Pourous Single Expansion Ramp Nozzle by : K. J. Yamamoto
Download or read book Supersonic Jet Noise Reduction by a Pourous Single Expansion Ramp Nozzle written by K. J. Yamamoto and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Study of Supersonic Jet Noise Reduction Using LES by : Haukur Elvar Hafsteinsson
Download or read book Study of Supersonic Jet Noise Reduction Using LES written by Haukur Elvar Hafsteinsson and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Shock Structure and Noise of Supersonic Jets in Simulated Flight to Mach 0.4 by : Thomas D. Norum
Download or read book Shock Structure and Noise of Supersonic Jets in Simulated Flight to Mach 0.4 written by Thomas D. Norum and published by . This book was released on 1988 with total page 212 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 Supersonic Coaxial Jet Noise Predictions by : Milo D. Dahl
Download or read book Supersonic Coaxial Jet Noise Predictions written by Milo D. Dahl and published by . This book was released on 1995 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Mixing Noise Reduction for Rectangular Supersonic Jets by Nozzle Shaping and Induced Screech Mixing by : Edward J. Rice
Download or read book Mixing Noise Reduction for Rectangular Supersonic Jets by Nozzle Shaping and Induced Screech Mixing written by Edward J. Rice and published by . This book was released on 1993 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: