Aeroacoustics Of Open Rotors PDF Download
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| Author | : Edmane Envia |
| Publisher | : BiblioGov |
| Total Pages | : 26 |
| Release | : 2013-06 |
| Genre | : |
| ISBN | : 9781289042059 |
Download Open Rotor Aeroacoustic Modeling Book in PDF, ePub and Kindle
Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.
| Author | : Jean Prieur |
| Publisher | : |
| Total Pages | : 114 |
| Release | : 1997 |
| Genre | : |
| ISBN | : |
Download Aeroacoustics of Open Rotors Book in PDF, ePub and Kindle
| Author | : Envia Edmane |
| Publisher | : BiblioGov |
| Total Pages | : 26 |
| Release | : 2013-07 |
| Genre | : |
| ISBN | : 9781289151188 |
Download Open Rotor Aeroacoustic Modelling Book in PDF, ePub and Kindle
Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.
| Author | : National Aeronautics and Space Adm Nasa |
| Publisher | : Independently Published |
| Total Pages | : 26 |
| Release | : 2019-01-14 |
| Genre | : Science |
| ISBN | : 9781793976932 |
Download Prediction of the Aero-Acoustic Performance of Open Rotors Book in PDF, ePub and Kindle
The rising cost of jet fuel has renewed interest in contrarotating open rotor propulsion systems. Contemporary design methods offer the potential to maintain the inherently high aerodynamic efficiency of open rotors while greatly reducing their noise output, something that was not feasible in the 1980's designs. The primary source mechanisms of open rotor noise generation are thought to be the front rotor wake and tip vortex interacting with the aft rotor. In this paper, advanced measurement techniques and high-fidelity prediction tools are used to gain insight into the relative importance of the contributions to the open rotor noise signature of the front rotor wake and rotor tip vortex. The measurements include three-dimensional particle image velocimetry of the intra-rotor flowfield and the acoustic field of a model-scale open rotor. The predictions provide the unsteady flowfield and the associated acoustic field. The results suggest that while the front rotor tip vortex can have a significant influence on the blade passing tone noise produced by the aft rotor, the front rotor wake plays the decisive role in the generation of the interaction noise produced as a result of the unsteady aerodynamic interaction of the two rotors. At operating conditions typical of takeoff and landing operations, the interaction noise level is easily on par with that generated by the individual rotors, and in some cases is even higher. This suggests that a comprehensive approach to reducing open rotor noise should include techniques for mitigating the wake of the front rotor as well as eliminating the interaction of the front rotor tip vortex with the aft rotor blade tip. VanZante, Dale and Envia, Edmane Glenn Research Center WBS 699959.02.07.03.01
| Author | : National Aeronautics and Space Adm Nasa |
| Publisher | : Independently Published |
| Total Pages | : 32 |
| Release | : 2019-01-13 |
| Genre | : Science |
| ISBN | : 9781793923035 |
Download Open Rotor Noise Prediction at NASA Langley - Capabilities, Research and Development Book in PDF, ePub and Kindle
The high fuel prices of recent years have caused the operating cost of the airlines to soar. In an effort to bring down the fuel consumption, the major aircraft engine manufacturers are now taking a fresh look at open rotors for the propulsion of future airliners. Open rotors, also known as propfans or unducted fans, can offer up to 30 per cent improvement in efficiency compared to high bypass engines of 1980 vintage currently in use in most civilian aircraft. NASA Langley researchers have contributed significantly to the development of aeroacoustic technology of open rotors. This report discusses the current noise prediction technology at Langley and reviews the input data requirements, strengths and limitations of each method as well as the associated problems in need of attention by the researchers. We present a brief history of research on the aeroacoustics of rotating blade machinery at Langley Research Center. We then discuss the available noise prediction codes for open rotors developed at NASA Langley and their capabilities. In particular, we present the two useful formulations used for the computation of noise from subsonic and supersonic surfaces. Here we discuss the open rotor noise prediction codes ASSPIN and one based on Ffowcs Williams-Hawkings equation with penetrable data surface (FW - Hpds). The scattering of sound from surfaces near the rotor are calculated using the fast scattering code (FSC) which is also discussed in this report. Plans for further improvements of these codes are given. Farassat, Fereidoun Langley Research Center WBS:561581.02.08.07.18.03
| Author | : Fereidoun Farassat |
| Publisher | : BiblioGov |
| Total Pages | : 34 |
| Release | : 2013-07 |
| Genre | : |
| ISBN | : 9781289235178 |
Download Open Rotor Noise Prediction at Nasa Langley Book in PDF, ePub and Kindle
The high fuel prices of recent years have caused the operating cost of the airlines to soar. In an effort to bring down the fuel consumption, the major aircraft engine manufacturers are now taking a fresh look at open rotors for the propulsion of future airliners. Open rotors, also known as propfans or unducted fans, can offer up to 30 per cent improvement in efficiency compared to high bypass engines of 1980 vintage currently in use in most civilian aircraft. NASA Langley researchers have contributed significantly to the development of aeroacoustic technology of open rotors. This report discusses the current noise prediction technology at Langley and reviews the input data requirements, strengths and limitations of each method as well as the associated problems in need of attention by the researchers. We present a brief history of research on the aeroacoustics of rotating blade machinery at Langley Research Center. We then discuss the available noise prediction codes for open rotors developed at NASA Langley and their capabilities. In particular, we present the two useful formulations used for the computation of noise from subsonic and supersonic surfaces. Here we discuss the open rotor noise prediction codes ASSPIN and one based on Ffowcs Williams-Hawkings equation with penetrable data surface (FW - Hpds). The scattering of sound from surfaces near the rotor are calculated using the fast scattering code (FSC) which is also discussed in this report. Plans for further improvements of these codes are given.
| Author | : Jean Prieur |
| Publisher | : |
| Total Pages | : 117 |
| Release | : 1997 |
| Genre | : |
| ISBN | : |
Download Aeroacoustics of Open Rotors Book in PDF, ePub and Kindle
| Author | : Stewart Glegg |
| Publisher | : Academic Press |
| Total Pages | : 554 |
| Release | : 2017-02-15 |
| Genre | : Science |
| ISBN | : 0128097930 |
Download Aeroacoustics of Low Mach Number Flows Book in PDF, ePub and Kindle
Aeroacoustics of Low Mach Number Flows: Fundamentals, Analysis, and Measurement provides a comprehensive treatment of sound radiation from subsonic flow over moving surfaces, which is the most widespread cause of flow noise in engineering systems. This includes fan noise, rotor noise, wind turbine noise, boundary layer noise, and aircraft noise. Beginning with fluid dynamics, the fundamental equations of aeroacoustics are derived and the key methods of solution are explained, focusing both on the necessary mathematics and physics. Fundamentals of turbulence and turbulent flows, experimental methods and numerous applications are also covered. The book is an ideal source of information on aeroacoustics for researchers and graduate students in engineering, physics, or applied math, as well as for engineers working in this field. Supplementary material for this book is provided by the authors on the website www.aeroacoustics.net. The website provides educational content designed to help students and researchers in understanding some of the principles and applications of aeroacoustics, and includes example problems, data, sample codes, course plans and errata. The website is continuously being reviewed and added to. Explains the key theoretical tools of aeroacoustics, from Lighthill’s analogy to the Ffowcs Williams and Hawkings equation Provides detailed coverage of sound from lifting surfaces, boundary layers, rotating blades, ducted fans and more Presents the fundamentals of sound measurement and aeroacoustic wind tunnel testing
| Author | : Harvey H. Hubbard |
| Publisher | : |
| Total Pages | : 620 |
| Release | : 1991 |
| Genre | : Aerodynamic noise |
| ISBN | : |
Download Aeroacoustics of Flight Vehicles Book in PDF, ePub and Kindle
| Author | : Alexander Dang Quang Truong |
| Publisher | : |
| Total Pages | : 143 |
| Release | : 2012 |
| Genre | : |
| ISBN | : 9781267711649 |
Download Acoustic Simulation of Counter-rotating Open Rotor Noise Using Very Small Scale Model Book in PDF, ePub and Kindle
This work examines the potential of very-small scale open rotor model to simulate the acoustics of large scale counter-rotating open rotor (CROR). Experiments employed a one-forty-fifth scale model of a rotor used in flight test in the 1980s. The historical counter-rotating rotor set called F7/A7 was designed by General Electric. The rotors were powered by two high performance radio controlled electric brushless motors and operated at realistic takeoff conditions. Aeroacoustic surveys were conducted inside an anechoic chamber using a 24-microphone polar array. In addition, we present parametric subscale experimental studies of open rotor noise shielding in two basic configurations. The first configuration used a flat aluminum rectangular shield. The second configuration, called N2AEXTE, utilize a flat aluminum shield with the planform shape of a Hybrid Wing Body (HWB). For both configurations the axial distance between the shield trailing edge and rotor was varied. The isolated subscale test appears to capture the tonal content and directivity of open rotor noise. Rotor-alone tones dominated the directivities near 90 degrees. The first interaction tone was most significant away from the rotor plane. Shielding using the rectangular plate and HWB planform can be substantial, up to 20dB of attenuation at some polar angles for tonal noise. Complexities of shielding include some amplification at low polar angles relative to the downstream direction. Amplifications upwards of 5 dB occurred at specific interaction tones. Shielding experiments clearly indicate that increasing shielding length also increases noise reduction. These strong noise reduction results indicate the great potential of open rotor noise shielding.
