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Jet Noise Modeling For Coannular Nozzles Including The Effects Of Chevrons
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Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721942343 Total Pages :212 pages Book Rating :4.9/5 (423 download)
Book Synopsis Jet Noise Modeling for Coannular Nozzles Including the Effects of Chevrons by : National Aeronautics and Space Administration (NASA)
Download or read book Jet Noise Modeling for Coannular Nozzles Including the Effects of Chevrons written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-27 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of good predictive models for jet noise has always been plagued by the difficulty in obtaining good quality data over a wide range of conditions in different facilities.We consider such issues very carefully in selecting data to be used in developing our model. Flight effects are of critical importance, and none of the means of determining them are without significant problems. Free-jet flight simulation facilities are very useful, and can provide meaningful data so long as they can be analytically transformed to the flight frame of reference. In this report we show that different methodologies used by NASA and industry to perform this transformation produce very different results, especially in the rear quadrant; this compels us to rely largely on static data to develop our model, but we show reasonable agreement with simulated flight data when these transformation issues are considered. A persistent problem in obtaining good quality data is noise generated in the experimental facility upstream of the test nozzle: valves, elbows, obstructions, and especially the combustor can contribute significant noise, and much of this noise is of a broadband nature, easily confused with jet noise. Muffling of these sources is costly in terms of size as well as expense, and it is particularly difficult in flight simulation facilities, where compactness of hardware is very important, as discussed by Viswanathan (Ref. 13). We feel that the effects of jet density on jet mixing noise may have been somewhat obscured by these problems, leading to the variable density exponent used in most jet noise prediction procedures including our own. We investigate this issue, applying Occam s razor, (e.g., Ref. 14), in a search for the simplest physically meaningful model that adequately describes the observed phenomena. In a similar vein, we see no reason to reject the Lighthill approach; it provides a very solid basis upon which to build a predictive procedure, as we believe we dem
Book Synopsis Jet Noise Modeling for Coannular Nozzles Including the Effects of Chevrons by :
Download or read book Jet Noise Modeling for Coannular Nozzles Including the Effects of Chevrons written by and published by . This book was released on 2003 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721139750 Total Pages :106 pages Book Rating :4.1/5 (397 download)
Book Synopsis Jet Noise Modeling for Supersonic Business Jet Application by : National Aeronautics and Space Administration (NASA)
Download or read book Jet Noise Modeling for Supersonic Business Jet Application written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-15 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document describes the development of an improved predictive model for coannular jet noise, including noise suppression modifications applicable to small supersonic-cruise aircraft such as the Supersonic Business Jet (SBJ), for NASA Langley Research Center (LaRC). For such aircraft a wide range of propulsion and integration options are under consideration. Thus there is a need for very versatile design tools, including a noise prediction model. The approach used is similar to that used with great success by the Modern Technologies Corporation (MTC) in developing a noise prediction model for two-dimensional mixer ejector (2DME) nozzles under the High Speed Research Program and in developing a more recent model for coannular nozzles over a wide range of conditions. If highly suppressed configurations are ultimately required, the 2DME model is expected to provide reasonable prediction for these smaller scales, although this has not been demonstrated. It is considered likely that more modest suppression approaches, such as dual stream nozzles featuring chevron or chute suppressors, perhaps in conjunction with inverted velocity profiles (IVP), will be sufficient for the SBJ. Stone, James R. and Krejsa, Eugene A. and Clark, Bruce J. Glenn Research Center NAS3-00178; WBS-22-781-30-12
Book Synopsis Jet Noise Modeling for Supersonic Business Jet Application by : James R. Stone
Download or read book Jet Noise Modeling for Supersonic Business Jet Application written by James R. Stone and published by BiblioGov. This book was released on 2013-07 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document describes the development of an improved predictive model for coannular jet noise, including noise suppression modifications applicable to small supersonic-cruise aircraft such as the Supersonic Business Jet (SBJ), for NASA Langley Research Center (LaRC). For such aircraft a wide range of propulsion and integration options are under consideration. Thus there is a need for very versatile design tools, including a noise prediction model. The approach used is similar to that used with great success by the Modern Technologies Corporation (MTC) in developing a noise prediction model for two-dimensional mixer ejector (2DME) nozzles under the High Speed Research Program and in developing a more recent model for coannular nozzles over a wide range of conditions. If highly suppressed configurations are ultimately required, the 2DME model is expected to provide reasonable prediction for these smaller scales, although this has not been demonstrated. It is considered likely that more modest suppression approaches, such as dual stream nozzles featuring chevron or chute suppressors, perhaps in conjunction with inverted velocity profiles (IVP), will be sufficient for the SBJ.
Book Synopsis Evaluation of Some Recent Jet Noise Reduction Concepts by :
Download or read book Evaluation of Some Recent Jet Noise Reduction Concepts written by and published by . This book was released on 2003 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper discusses RANS based numerical simulations of a 1/10th scale over-expanded supersonic plume (resembling that of an F-18 aircraft) with chevrons used as passive noise reduction devices. Three variant designs of the chevrons mounted in specified azimuthal arrangements around the baseline nozzle exit are evaluated. A major effect of the chevrons is to amplify the Mach disc size and move it closer to the nozzle exit. For these over-expanded exhausts, the chevrons must extend sufficiently deep into the plume core stream to reduce jet noise levels. Results from our simulations are in nominal accord with the experimental observations (primarily noise measurements) as ascertained by examining the flow structure, and via using jet noise prediction codes. Evaluation of the thrust loss produced by these devices is found to be minimal except for the one chevron configuration that provided maximum noise reduction. Our studies indicate that noise reduction devices which work for laboratory model jets may have to be revised to have them work for the real engine due to complexities in the internal mixing which cannot be replicated at laboratory scale. We discuss issues related to these differences and with real aircraft effects such as plume/plume interactions and installation effects, and we present a complete aircraft/dual engine plume simulation using innovative multi-element unstructured gridding.
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 A Correlation of Mixing Noise from Coannular Jets with Inverted Flow Profiles by : S. Paul Pao
Download or read book A Correlation of Mixing Noise from Coannular Jets with Inverted Flow Profiles written by S. Paul Pao and published by . This book was released on 1979 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Data are correlated for jet mixing noise from coannular jets with inverted flow velocity profiles. The acoustic performance of coannular jets is compared to the performance of a hypothetical single jet with the same total mass flow, thrust, and total enthalpy flow as the coannular jet. The study shows that coannular jets with velocity ratios greater than 1.2 produce less noise than their corresponding equivalent tests and that optimum noise reduction of coannular jets in the data set occurs within a range of equivalent velocities between 500 and 700 meters per second and velocity ratios between 1.6 and 2.3. The maximum sound power reduction is found to be about 4 decibels. Directivity indices and a special set of spectral curves were developed to describe the characteristic double peak spectra of coannular jet noise. The temperature ratio between the inner and outer streams was not found to be important in this acoustic correlation. However, the mean temperature effect was included in the computations of sound pressure levels.
Book Synopsis Static and wind tunnel near-field/far-field jet noise measurements from model scale single-flow baseline and suppressor nozzles by : Carl Lewis Jaeck
Download or read book Static and wind tunnel near-field/far-field jet noise measurements from model scale single-flow baseline and suppressor nozzles written by Carl Lewis Jaeck and published by . This book was released on 1977 with total page 116 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 Static and Wind Tunnel Near-field/far Field Jet Noise Measurements from Model Scale Single-flow Baseline and Suppressor Nozzles. Volume 2: Forward Speed Effects by :
Download or read book Static and Wind Tunnel Near-field/far Field Jet Noise Measurements from Model Scale Single-flow Baseline and Suppressor Nozzles. Volume 2: Forward Speed Effects written by and published by . This book was released on 1976 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Method for Predicting the Noise Levels of Coannular Jets with Inverted Velocity Profiles by : J. W. Russell
Download or read book A Method for Predicting the Noise Levels of Coannular Jets with Inverted Velocity Profiles written by J. W. Russell and published by . This book was released on 1979 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: A coannular jet was equated with a single stream equivalent jet with the same mass flow, energy, and thrust. The acoustic characteristics of the coannular jet were then related to the acoustic characteristics of the single jet. Forward flight effects were included by incorporating a forward exponent, a Doppler amplification factor, and a Strouhal frequency shift. Model test data, including 48 static cases and 22 wind tunnel cases, were used to evaluate the prediction method. For the static cases and the low forward velocity wind tunnel cases, the spectral mean square pressure correlation coefficients were generally greater than 90 percent, and the spectral sound pressure level standard deviation were generally less than 3 decibels. The correlation coefficient and the standard deviation were not affected by changes in equivalent jet velocity. Limitations of the prediction method are also presented.
Book Synopsis Air Transport and Operations by : R. Curran
Download or read book Air Transport and Operations written by R. Curran and published by IOS Press. This book was released on 2012 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the proceedings of the joint conference held in Delft, the Netherlands inJune 2012, incorporating the 3rd International Air Transport Operations Symposium ATOS, the 3rd Association of Scientific Development in Air Traffic Management in Europe ASDASeminar, the 6th International Meeting for Aviation Products Support Processes IMAPP and the 2012Complex World Seminar. The book includes the majority of academic papers presented at the conference, and provides a wide overview of the issues currently of importance in the world of air transport.pIOS Press is an international science, technical and medical publisher
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.
Book Synopsis Simple Jet Noise Reduction Methods by : Caroline J. Cooper
Download or read book Simple Jet Noise Reduction Methods written by Caroline J. Cooper and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Shock Associated Noise Reduction from Inverted-velocity-profile Coannular Jets by : H. K. Tanna
Download or read book Shock Associated Noise Reduction from Inverted-velocity-profile Coannular Jets written by H. K. Tanna and published by . This book was released on 1981 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Static and Wind Tunnel Near-field/far-field Jet Noise Measurements from Model Scale Single-flow Baseline and Suppressor Nozzles. Volume 1: Noise Source Locations and Extrapolation of Static Free-field Jet Noise Data by :
Download or read book Static and Wind Tunnel Near-field/far-field Jet Noise Measurements from Model Scale Single-flow Baseline and Suppressor Nozzles. Volume 1: Noise Source Locations and Extrapolation of Static Free-field Jet Noise Data written by and published by . This book was released on 1976 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Semi-empirical Model for Coannular Nozzle Component Noise Extraction and Correlation Including the Effects of Noise Reduction Services by : James R. Stone
Download or read book Semi-empirical Model for Coannular Nozzle Component Noise Extraction and Correlation Including the Effects of Noise Reduction Services written by James R. Stone and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
