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.
Download or read book Transonic Rotor Noise Theoretical and Experimental Comparisons written by and published by . This book was released on 1980 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two complementary methods of describing the high-speed rotor noise problem are discussed. The first method uses the second-order transonic potential equation to define and characterize the nature of the aerodynamic and acoustic fields and to explain the appearance of radiating shock waves. The second employs the Ffowcs Williams and Hawkings equation to successfully calculate the acoustic far-field. Good agreement between theoretical and experimental waveforms is shown for transonic hover tip Mach numbers from 0.8 to 0.9. (Author).
Download or read book The Computation and Analysis of Helicopter Impulsive Noise written by Xue Yu and published by . This book was released on 1994 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book In Flight Far Field Measurement of Helicopter Impulsive Noise written by and published by . This book was released on 1976 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: An in-flight technique for measuring UH-1H helicopter impulsive noise (sometimes called 'blade slap') by stationkeeping with a quiet instrumented lead aircraft was found to be highly successful. Far-field quantitative acoustic waveforms and radiation patterns were easily obtained over a wide, continuous range of UH-1H flight conditions, including several areas known to produce annoying acoustic radiation. The data collected using this technique were not (to any significant degree) contaminated by transmission path distortions that have hindered measurement efforts in the past. The two major finding of this initial measurement program were: (1) Judging the occurrence and severity of a helicopter's radiated impulsive noise signature from cabin-based noise measurements can be misleading. For the UH-1H helicopter, reduction in cabin audible impulsive noise levels may constitute a necessary but certainly not sufficient to indicate that far-field impulsive noise radiation has been reduced. The following three distinct types of impulsive noise are radiated by the Un-1H helicopter while flying between 80 and 115 knots at descent rates from zero to 1000 ft/min: (a) A series of positive pressure pulses believed to be related to blade-tip vortex interaction. These pulses are responsible for the crisp popping sound of the radiated noise; (b) A negative pressure disturbance that rapidly increases in amplitude with forward velocity, becoming quite intense and sawtoothed in shape at 115 knots IAS; and (c) A narrow positive pressure spike that closely follows that sawtooth-shaped negative pressure pulse at high airspeeds (115 knots).
Download or read book Recent Advances in Aeroacoustics written by A. Krothapalli and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Joint Institute for Aeronautics and Acoustics at Stanford University was established in October 1973 to provide an academic environment for long-term cooperative research between Stanford and NASA Ames Research Center. Since its establishment, the Institute has conducted theoretical and experimental work in the areas of aerodynamics, acoustics, fluid mechanics, flight dynamics, guidance and control, and human factors. This research has involved Stanford faculty, research associates, graduate students, and many distinguished visitors in collaborative efforts with the research staff of NASA Ames Research Center. The occasion of the Institute's tenth anniversary was used to reflect back on where that research has brought us, and to consider where our endeavors should be directed next. Thus, an International Symposium was held to review recent advances in the fields relevant to the activities of the Institute and to discuss the areas of research to be undertaken in the future. This anniversary was also chosen as an opportunity to honor one of the Institute's founders and its director, Professor Krishnamurty Karamcheti. It has been his crea tive inspiration that has provided the ideal research environment at the Joint Institute.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Correlation of Helicopter Impulsive Noise from Blade vortex Interaction with Rotor Mean Inflow written by Andrew B. Connor and published by . This book was released on 1987 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Symposium on Recent Advances in Aerodynamics and Aeroacoustics August 22 to 26 1983 Abstracts written by Joint Institute for Aeronautics and Acoustics and published by . This book was released on with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Helicopter Noise Part 1 Review and theoretical study written by John W. Leverton and published by . This book was released on 1968 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aeronautical Engineering written by and published by . This book was released on 1991 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1984-04 with total page 1364 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA SP written by and published by . This book was released on 1988 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aeroacoustics of Flight Vehicles written by Harvey H. Hubbard and published by . This book was released on 1991 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Blade Vortex Interaction Noise Characteristics of a Utility Helicopter at 1 4 Scale written by and published by . This book was released on 1984 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Reference Publication written by and published by . This book was released on 1977 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Shock and Vibration Digest written by and published by . This book was released on 1985 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Army Rotorcraft Technology Volume 2 Materials and Structures Propulsion and Drive Systems Flight Dynamics and Control and Acoustics written by and published by . This book was released on 1988 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt:
