Reduction Of Blade Vortex Interaction Noise Using Higher Harmonic Pitch Control PDF Download
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Total Pages | : 22 |
Release | : 1989 |
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Download Reduction of Blade-vortex Interaction Noise Using Higher Harmonic Pitch Control Book in PDF, ePub and Kindle
An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in the Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4- 5 dB) were found for low-speed descent conditions, where helicopter BVI noise was most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.
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Total Pages | : 458 |
Release | : 1992 |
Genre | : Aeronautics |
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Download NASA Technical Memorandum Book in PDF, ePub and Kindle
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Total Pages | : 15 |
Release | : 1995 |
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Download Effect of Wake Structure on Blade-Vortex Interaction Phenomena: Acoustic Prediction and Validation Book in PDF, ePub and Kindle
During the Higher Harmonic Control Aeroacoustic Rotor Test, extensive measurements of the rotor aerodynamics, the far-field acoustics, the wake geometry and the blade motion for powered, descent, flight conditions were made. These measurements have been used to validate and improve the prediction of blade-vortex interaction (BVI) noise. The improvements made to the BVI modeling after the evaluation of the test data are discussed. The effects of these improvements on the acoustic-pressure predictions are shown. These improvements include re-structuring the wake, modifying the core size, incorporating the measured blade motion into the calculations and attempting to improve the dynamic blade response. A comparison of four different implementations of the Ffowcs Williams and Hawkings equation is presented. A common set of aerodynamic input has been used for this comparison. (AN).
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Total Pages | : 702 |
Release | : 1995 |
Genre | : Aeronautics |
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Download Scientific and Technical Aerospace Reports Book in PDF, ePub and Kindle
Author | : Wel-Chong Sim |
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Total Pages | : 360 |
Release | : 1996 |
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Download Blade-vortex Interaction Noise Generation and Directionality Book in PDF, ePub and Kindle
Author | : Wayne Johnson |
Publisher | : Cambridge University Press |
Total Pages | : 949 |
Release | : 2013-04-29 |
Genre | : Technology & Engineering |
ISBN | : 1107355281 |
Download Rotorcraft Aeromechanics Book in PDF, ePub and Kindle
A rotorcraft is a class of aircraft that uses large-diameter rotating wings to accomplish efficient vertical take-off and landing. The class encompasses helicopters of numerous configurations (single main rotor and tail rotor, tandem rotors, coaxial rotors), tilting proprotor aircraft, compound helicopters, and many other innovative configuration concepts. Aeromechanics covers much of what the rotorcraft engineer needs: performance, loads, vibration, stability, flight dynamics, and noise. These topics include many of the key performance attributes and the often-encountered problems in rotorcraft designs. This comprehensive book presents, in depth, what engineers need to know about modelling rotorcraft aeromechanics. The focus is on analysis, and calculated results are presented to illustrate analysis characteristics and rotor behaviour. The first third of the book is an introduction to rotorcraft aerodynamics, blade motion, and performance. The remainder of the book covers advanced topics in rotary wing aerodynamics and dynamics.
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Total Pages | : 890 |
Release | : 2004 |
Genre | : Technology |
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Download NASA Tech Briefs Book in PDF, ePub and Kindle
Author | : Todd Darwin Ringler |
Publisher | : |
Total Pages | : 332 |
Release | : 1992 |
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Download The Directionality of Blade-vortex Interaction Noise Book in PDF, ePub and Kindle
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Total Pages | : 538 |
Release | : 1991 |
Genre | : Aeronautics |
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Download Aeronautical Engineering Book in PDF, ePub and Kindle
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Total Pages | : 168 |
Release | : 1991 |
Genre | : Small business |
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Download Small Business Innovation Research Book in PDF, ePub and Kindle