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Helicopter Main Rotor Noise
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Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781722429034 Total Pages :68 pages Book Rating :4.4/5 (29 download)
Book Synopsis Helicopter Main-Rotor Noise by : National Aeronautics and Space Administration (NASA)
Download or read book Helicopter Main-Rotor Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-10 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic data from a test of a 40 percent model MBB BO-105 helicopter main rotor are scaled to equivalent full-scale flyover cases. The test was conducted in the anechoic open test section of the German-Dutch Windtunnel (DNW). The measured data are in the form of acoustic pressure time histories and spectra from two out-of-flow microphones underneath and foward of the model. These are scaled to correspond to measurements made at locations 150 m below the flight path of a full-scale rotor. For the scaled data, a detailed analysis is given for the identification in the data of the noise contributions from different rotor noise sources. Key results include a component breakdown of the noise contributions, in terms of noise criteria calculations of a weighted sound pressure level (dBA) and perceived noise level (PNL), as functions of rotor advance ratio and descent angle. It is shown for the scaled rotor that, during descent, impulsive blade-vortex interaction (BVI) noise is the dominant contributor to the noise. In level flight and mild climb, broadband blade-turbulent wake interaction (BWI) noise is dominant due to the absence of BVI activity. At high climb angles, BWI is reduced and self-noise from blade boundary-layer turbulence becomes the most prominent. Brooks, Thomas F. and Jolly, J. Ralph, Jr. and Marcolini, Michael A. Langley Research Center...
Book Synopsis Helicopter Main-rotor Noise by : Thomas F. Brooks
Download or read book Helicopter Main-rotor Noise written by Thomas F. Brooks and published by . This book was released on 1988 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Helicopter Main-rotor Noise: Determination of Source Contributions Using Scaled Model Data by : Thomas F. Brooks
Download or read book Helicopter Main-rotor Noise: Determination of Source Contributions Using Scaled Model Data written by Thomas F. Brooks and published by . This book was released on 1988 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Helicopter Impulsive Noise: Theoretical and Experimental Status by : F. H. Schmitz
Download or read book Helicopter Impulsive Noise: Theoretical and Experimental Status written by F. H. Schmitz and published by . This book was released on 1983 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanisms is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanisms of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.
Book Synopsis Research Investigation of Helicopter Main Rotor/tail Rotor Interaction Noise by : J. Fitzgerald
Download or read book Research Investigation of Helicopter Main Rotor/tail Rotor Interaction Noise written by J. Fitzgerald and published by . This book was released on 1988 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Revolutionary Concepts for Helicopter Noise Reduction: SILENT Program by : Bryan Edwards
Download or read book Revolutionary Concepts for Helicopter Noise Reduction: SILENT Program written by Bryan Edwards and published by . This book was released on 2002 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Research Investigation of Helicopter Main Rotor/tail Rotor Interaction Noise by : J. Fitzgerald
Download or read book Research Investigation of Helicopter Main Rotor/tail Rotor Interaction Noise written by J. Fitzgerald and published by . This book was released on 1988 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Study of Rotor Broadband Noise Mechanisms and Helicopter Tail Rotor Noise by :
Download or read book A Study of Rotor Broadband Noise Mechanisms and Helicopter Tail Rotor Noise written by and published by . This book was released on 1990 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Two-Dimensional Fourier Transform Applied to Helicopter Flyover Noise by : Odilyn L. Santa Maria
Download or read book Two-Dimensional Fourier Transform Applied to Helicopter Flyover Noise written by Odilyn L. Santa Maria and published by . This book was released on 1999 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rotorcraft Noise written by and published by . This book was released on 1982 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Revolutionary Concepts for Helicopter Noise Reduction by : Bryan Edwards
Download or read book Revolutionary Concepts for Helicopter Noise Reduction written by Bryan Edwards and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As part of a NASA initiative to reduce helicopter main rotor noise, a Phase 1 study has been performed of candidate noise reduction concepts. Both conventional and novel design technologies have been analyzed that reduce the community impact of helicopter operations. In this study the noise reduction potential and design implications are assessed for conventional means of noise reduction. e.g., tip speed reduction, tip shapes and airfoil tailoring, and for two innovative design concepts: modulated blade spacing and x-force control. Main rotor designs that incorporate modulated blade spacing are shown to have reduced peak noise levels in most flight operations. X-force control alters the helicopter's force balance whereby the miss distance between main rotor blades and shed vortices can be controlled. . This control provides a high potential to mitigate BVI noise radiation.
Book Synopsis Helicopter Main-rotor Speed Effects on Far-field Acoustic Levels by :
Download or read book Helicopter Main-rotor Speed Effects on Far-field Acoustic Levels written by and published by . This book was released on 1987 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781720710745 Total Pages :88 pages Book Rating :4.7/5 (17 download)
Book Synopsis Revolutionary Concepts for Helicopter Noise Reduction by : National Aeronautics and Space Administration (NASA)
Download or read book Revolutionary Concepts for Helicopter Noise Reduction written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-04 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: As part of a NASA initiative to reduce helicopter main rotor noise, a Phase 1 study has been performed of candidate noise reduction concepts. Both conventional and novel design technologies have been analyzed that reduce the community impact of helicopter operations. In this study the noise reduction potential and design implications are assessed for conventional means of noise reduction, e.g., tip speed reduction, tip shapes and airfoil tailoring, and for two innovative design concepts: modulated blade spacing and x-force control. Main rotor designs that incorporate modulated blade spacing are shown to have reduced peak noise levels in most flight operations. X-force control alters the helicopter's force balance whereby the miss distance between main rotor blades and shed vortices can be controlled. This control provides a high potential to mitigate BVI noise radiation. Each concept is evaluated using best practice design and analysis methods, achieving the study's aim to significantly reduce noise with minimal performance degradation and no vibration increase. It is concluded that a SILENT main rotor design, incorporating the modulated blade spacing concept, offers significantly reduced noise levels and the potential of a breakthrough in how a helicopter's sound is perceived and judged. The SILENT rotor represents a definite advancement in the state-of-the-art and is selected as the design concept for demonstration in Phase 2. A Phase 2 Implementation Plan is developed for whirl cage and wind tunnel evaluations of a scaled model SILENT rotor.Edwards, Bryan and Cox, Charles and Booth, Earl R., Jr. (Technical Monitor)Langley Research CenterAIRCRAFT NOISE; NOISE REDUCTION; NASA PROGRAMS; ROTARY WING AIRCRAFT; AEROACOUSTICS; SOUND WAVES; WAVEFORMS; VORTICES; WIND TUNNELS; AIRFOILS; BLADE-VORTEX INTERACTION
Book Synopsis The Development of Experimental Techniques for the Study of Helicopter Rotor Noise by :
Download or read book The Development of Experimental Techniques for the Study of Helicopter Rotor Noise written by and published by . This book was released on 1974 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Psychoacoustic Testing of Modulated Blade Spacing for Main Rotors by : Bryan Edwards
Download or read book Psychoacoustic Testing of Modulated Blade Spacing for Main Rotors written by Bryan Edwards and published by . This book was released on 2002 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: Psychoacoustic testing of simulated helicopter main rotor noise is described, and the subjective results are presented. The objective of these tests was to evaluate the potential acoustic benefits of main rotors with modulated (uneven) blade spacing. Sound simulations were prepared for six main rotor configurations. A baseline 4-blade main rotor with regular blade spacing was based on the Bell Model 427 helicopter. A 5-blade main rotor with regular spacing was designed to approximate the performance of the 427, but at reduced tipspeed. Four modulated rotors - one with "optimum" spacing and three alternate configurations - were derived from the 5 bladed regular spacing rotor. The sounds were played to 2 subjects at a time, with care being taken in the speaker selection and placement to ensure that the sounds were identical for each subject.
Book Synopsis Evaluation of the Annoyance Due to Helicopter Rotor Noise by : Harry Sternfeld
Download or read book Evaluation of the Annoyance Due to Helicopter Rotor Noise written by Harry Sternfeld and published by . This book was released on 1978 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis New Computational Methods for the Prediction and Analysis of Helicopter Noise by : Roger C. Strawn
Download or read book New Computational Methods for the Prediction and Analysis of Helicopter Noise written by Roger C. Strawn and published by . This book was released on 1996 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "This paper describes several new methods to predict and analyze rotorcraft noise. These methods are: 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise."
