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Author: Mrunali Botre Publisher: ISBN: Category : Languages : en Pages :
Book Description
The main contribution from the current work is the enhancement of a comprehensive noise prediction system for rotorcraft and a methodology to analyze flight test procedures in the interest of understanding the noise source generation mechanisms and aid development of noise abatement procedures. This dissertation describes a rotorcraft noise prediction system and its development to incorporate time-dependent information--including trajectory, attitude, blade loads and rotor thrust--for predicting noise generated during a complex maneuver. The validation process is carried out by comparing the predicted noise levels (SELdBA, OASPL and A--weighted SPL) and processed flight test data. The examples considered are: level flight; descent flight; level turns; level, decelerating turns; and descending turns. This range of operations is considered to analyze the prediction system and understand its capabilities and deficiencies for future work. Overall the predicted noise levels were able to match the trends and levels within a 2--4 dB of that measured during the flight test. The time histories are studied in detail to understand the influence of events (such as steady flight conditions, with constant speed, roll angle or descent rate, and transient flight conditions, including roll-in and roll-out of turn, start and end of deceleration or acceleration) occurring during the flight procedure on noise levels and directivity. The key takeaways are that the noise prediction system was able to capture the noise levels but missed blade-vortex-interaction (BVI) noise directivity during some complex maneuvers. Transient maneuvers generate higher-harmonic loading and BVI noise and the intensity depends on the rate of change of flight conditions. The tail rotor not only contributes the thickness noise below the flight path but has significant contribution at sideline observer locations during a maneuver. The radiation distance and directivity have shown a stronger effect on noise levels than the harmonic noise sources. Lastly, the broadband noise dominates the A--weighted SPL for the steady maneuvers (except descent) and its importance is less during the transient flight segments. A final thing to note is that the noise generated during a 6° steady descent (the standard descent angle for approach) was much higher than any other complex procedures studied in the current work.
Author: Mrunali Botre Publisher: ISBN: Category : Languages : en Pages :
Book Description
The main contribution from the current work is the enhancement of a comprehensive noise prediction system for rotorcraft and a methodology to analyze flight test procedures in the interest of understanding the noise source generation mechanisms and aid development of noise abatement procedures. This dissertation describes a rotorcraft noise prediction system and its development to incorporate time-dependent information--including trajectory, attitude, blade loads and rotor thrust--for predicting noise generated during a complex maneuver. The validation process is carried out by comparing the predicted noise levels (SELdBA, OASPL and A--weighted SPL) and processed flight test data. The examples considered are: level flight; descent flight; level turns; level, decelerating turns; and descending turns. This range of operations is considered to analyze the prediction system and understand its capabilities and deficiencies for future work. Overall the predicted noise levels were able to match the trends and levels within a 2--4 dB of that measured during the flight test. The time histories are studied in detail to understand the influence of events (such as steady flight conditions, with constant speed, roll angle or descent rate, and transient flight conditions, including roll-in and roll-out of turn, start and end of deceleration or acceleration) occurring during the flight procedure on noise levels and directivity. The key takeaways are that the noise prediction system was able to capture the noise levels but missed blade-vortex-interaction (BVI) noise directivity during some complex maneuvers. Transient maneuvers generate higher-harmonic loading and BVI noise and the intensity depends on the rate of change of flight conditions. The tail rotor not only contributes the thickness noise below the flight path but has significant contribution at sideline observer locations during a maneuver. The radiation distance and directivity have shown a stronger effect on noise levels than the harmonic noise sources. Lastly, the broadband noise dominates the A--weighted SPL for the steady maneuvers (except descent) and its importance is less during the transient flight segments. A final thing to note is that the noise generated during a 6° steady descent (the standard descent angle for approach) was much higher than any other complex procedures studied in the current work.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781723511417 Category : Languages : en Pages : 276
Book Description
This document describes the theoretical methods used in the rotorcraft noise prediction system (ROTONET), which is a part of the NASA Aircraft Noise Prediction Program (ANOPP). The ANOPP code consists of an executive, database manager, and prediction modules for jet engine, propeller, and rotor noise. The ROTONET subsystem contains modules for the prediction of rotor airloads and performance with momentum theory and prescribed wake aerodynamics, rotor tone noise with compact chordwise and full-surface solutions to the Ffowcs-Williams-Hawkings equations, semiempirical airfoil broadband noise, and turbulence ingestion broadband noise. Flight dynamics, atmosphere propagation, and noise metric calculations are covered in NASA TM-83199, Parts 1, 2, and 3. Weir, Donald S. and Jumper, Stephen J. and Burley, Casey L. and Golub, Robert A. Langley Research Center NASA-TM-83199-PT-4, L-16700-PT-4, NAS 1.15:83199-PT-4 RTOP 532-06-37-01...
Author: Damaris Zachos Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The capability to predict aircraft noise is important in the development of acoustically aware aircraft. The first principles noise prediction model developed in this work evaluates medium weight-class aircraft models and a conceptual electric vertical takeoff and landing (eVTOL) design. This work contains four significant system improvements over the previous version of the noise prediction system: the incorporation of a dual compact thickness noise model, a standardized command file generation system for PSUHeloSim, an improved trim matrix solution for the HeloSim model, and the capability to "calibrate" broadband noise predictions. These enhancements, along with the definition of new helicopter models developed in this work will be described. Multiple helicopters were used to validate the noise prediction system. The Sikorsky S-76D and Bell 205 from Phase III of a joint NASA/FAA/ARMY flight test were simulated together with the Bell 407 and Bell 206 models from Phase II test by the same participants. The simulated noise from medium-weight class aircraft, such as the S-76D and Bell 205 was compared with the noise predictions for the lighter weight class aircraft, i.e., the Bell 407 and Bell 206. In particular, the S-76D was compared against the Bell 407 because both aircraft have four-bladed main rotors. The Bell 205 was compared with the Bell 206 because both aircraft have two-bladed main rotors. It was determined that the directionality of the thickness and broadband noise was similar between aircraft of different weight-classes. Loading noise magnitude and directivity changed between light and medium weight-class aircraft. A novel eVTOL concept based on the proposed Jaunt Journey aircraft was modeled in the noise prediction system for multiple steady-flight conditions. Comparisons were made with a baseline propeller to evaluate the effectiveness of a low-noise electric propeller design. The novel eVTOL rotor indicated low thickness and loading noise and significant reduction in broadband noise. A full model of the eVTOL aircraft was used to determine the noise of each of the propellers, main rotor, and full aircraft. The predicted noise of the novel eVTOL indicated lower total noise than a comparable conventional aircraft design.
Author: Oleksandr Zaporozhets Publisher: CRC Press ISBN: 0203888820 Category : Technology & Engineering Languages : en Pages : 432
Book Description
Aircraft noise has adverse impacts on passengers, airport staff and people living near airports, it thus limits the capacity of regional and international airports throughout the world. Reducing perceived noise of aircraft involves reduction of noise at source, along the propagation path and at the receiver. Effective noise control demands highly s
Author: Kalki Sharma Publisher: ISBN: Category : Languages : en Pages :
Book Description
In this thesis a noise prediction system is proposed for use in the design cycle of rotorcraft. The system is comprised of the design tool NASA Design and Analysis of Rotorcraft (NDARC), a noise prediction tool PSU-WOPWOP, and an intermediate tool called WOPIt. The system works by having NDARC set up the rotorcraft configuration for user specified constraints and analyze the performance for mission profiles and flight conditions, and then have PSU-WOPWOP perform the noise prediction for the configuration. The noise prediction is performed using first principles and semi-empirical models, and the tools of the system are chosen to perform tasks accurately and efficiently to allow for rapid turnaround of rotorcraft configurations by the designer. With the aid of this system, a designer can properly weigh the costs and benefits of a rotorcraft configuration based not only on performance data, but also upon its acoustic impact.
Author: Mrunali Botre
Author: Mrunali Botre
Author: National Aeronautics and Space Administration (NASA)
Author: Damaris Zachos
Author: Oleksandr Zaporozhets
Author: 
Author: John P. Raney
Author: 
Author: 
Author: Kalki Sharma
Author: John P. Raney