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Author: Lauren Weist Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Rotorcraft are a versatile and important class of vehicles within the aerospace industry, but they experience a highly varied aerodynamic environment that causes unique acoustic conditions. These acoustics are highly tonal, and are often found to cause community annoyance. Due to this, providing acoustic considerations for rotorcraft is a necessary area of research within the industry. To aid in these considerations, this thesis addresses noise via modeling through two noise prediction systems (NPS). To account for rotorcraft acoustics in the design stage, a low fidelity NPS, the NDARC NPS, was used. For acoustic considerations of existing helicopters, the high fidelity Penn State NPS is used. The low fidelity system, the NDARC NPS, is described first. As acoustic consideration in the design stage is not often conducted, development of a rapid tool to give to a designer is paramount. The NDARC NPS was created to fill this desire, and has been further developed as a part of this thesis. The NDARC NPS was fully exercised to identify issues and improve the system. Improvements to the blade-vortex interaction model, comprised of the Beddoes wake model and Vatistas implementation of the Biot-Savart law were completed. Improvements were made to the user interface, the complete suite of example cases was improved and expanded, and the User's Manual was completed. The mid-fidelity system, known as the Penn State NPS, is used to aid in providing guidance on noise abatement procedures for existing vehicles to aid in the reduction of community annoyance.In this work, the Penn State NPS was used to conduct several studies on the effects of real flight variations on noise. First, a study of longitudinal and vertical accelerations through the lens of flight path angle were conducted for the Sikorsky S-76D helicopter to understand how flight path angle and flight path angle rate changes can effect noise. Then, a study of helicopter configuration and the impact of weight and number of blades on noise was conducted. Four vehicles, the Sikorsky S-76D, the Bell 205, the Bell 407, and the Bell 206 were all analyzed in descent to understand how vehicle configuration influences noise.
Author: Lauren Weist Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Rotorcraft are a versatile and important class of vehicles within the aerospace industry, but they experience a highly varied aerodynamic environment that causes unique acoustic conditions. These acoustics are highly tonal, and are often found to cause community annoyance. Due to this, providing acoustic considerations for rotorcraft is a necessary area of research within the industry. To aid in these considerations, this thesis addresses noise via modeling through two noise prediction systems (NPS). To account for rotorcraft acoustics in the design stage, a low fidelity NPS, the NDARC NPS, was used. For acoustic considerations of existing helicopters, the high fidelity Penn State NPS is used. The low fidelity system, the NDARC NPS, is described first. As acoustic consideration in the design stage is not often conducted, development of a rapid tool to give to a designer is paramount. The NDARC NPS was created to fill this desire, and has been further developed as a part of this thesis. The NDARC NPS was fully exercised to identify issues and improve the system. Improvements to the blade-vortex interaction model, comprised of the Beddoes wake model and Vatistas implementation of the Biot-Savart law were completed. Improvements were made to the user interface, the complete suite of example cases was improved and expanded, and the User's Manual was completed. The mid-fidelity system, known as the Penn State NPS, is used to aid in providing guidance on noise abatement procedures for existing vehicles to aid in the reduction of community annoyance.In this work, the Penn State NPS was used to conduct several studies on the effects of real flight variations on noise. First, a study of longitudinal and vertical accelerations through the lens of flight path angle were conducted for the Sikorsky S-76D helicopter to understand how flight path angle and flight path angle rate changes can effect noise. Then, a study of helicopter configuration and the impact of weight and number of blades on noise was conducted. Four vehicles, the Sikorsky S-76D, the Bell 205, the Bell 407, and the Bell 206 were all analyzed in descent to understand how vehicle configuration influences noise.
Author: Publisher: ISBN: Category : Languages : en Pages : 54
Book Description
Sound exposure level (SEL) data from three Army helicopters were used to test a proposed method for calculating sideline decay developed for fixed-wing aircraft. The Federal Aviation Administration (FAA) and the U.S. Air Force (USAF) have adopted this method for use with fixed-wing aircraft, and it was desired to know if the same method could predict rotary-wing aircraft sideline decay with distance or if a more complex computer model is necessary. The procedure was found accurate for limited altitudes and slant distances. In addition, the sideline decay data were studied using variables known to affect sound attenuation. The purpose was to gain further insight into the mechanisms of sideline decay with distance. Variations in the results suggest an unknown mechanism is contributing to this attenuation. (Author).
Author: F. H. Schmitz Publisher: ISBN: Category : Languages : en Pages : 110
Book Description
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.
Author: Publisher: ISBN: 9780309374965 Category : Airplanes Languages : en Pages : 4
Book Description
"TRB's Airport Cooperative Research Program (ACRP) Research Results Digest 24: Recommended Community Noise Model Enhancements to Improve Prediction of Helicopter Activity Impacts provides an overview of research conducted to identify improvements to the most common methods for predicting helicopter community noise, including the research tasks, findings, final conclusions, and next steps. While the research did not attempt to identify which noise metric best predicts annoyance, it offers a computational methodology from which suggested metrics may be accurately determined." -- Publisher's description
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: Willca Villafana Publisher: ISBN: Category : Languages : en Pages :
Book Description
A rotorcraft noise prediction system has recently been developed as part of aproject to develop and evaluate helicopter noise abatement procedures for a rangeof aircraft. The aim of this thesis is to demonstrate the noise prediction systemcapabilities and then consider simple noise abatement procedures for three differenthelicopters of varying technology levels and maximum gross weights.First, the codes that have been assembled into the noise prediction system aredescribed. A brief presentation of acoustic theory on which the noise prediction isbased is given as a reminder. Then, the noise prediction system has been validatedwith the Bell 430 helicopter flying in a level forward flight. The prediction systemhas also demonstrated its capacity to predict blade vortex interaction (BVI) noiseand BVI noise reduction. Finally several abatement procedures have been examined.The two first ones underscored the benefits of flying higher and slower by usingthe S-76C+ as an example. Then, a S-76C+, Bell 430 and BK 117 helicopterswere compared in a level forward flight. The comparison ended up with surprisingresults about loading and broadband noise since they do not appear correlated tothe weight of the rotorcrafts. Yet, thickness noise results are expected since theyare related to the rotor tip speeds. Finally, the effects of descent angle and speedon BVI noise have been demonstrated during approach. A Bell 430 helicopter wasused for this study and the speed and angle of descent were varied separately whilekeeping all the other parameters constant.
Author: J. D. Leatherwood Publisher: ISBN: Category : Helicopters Languages : en Pages : 52
Book Description
This paper presents the results of a simulator study conducted to compare and validate various ride quality prediction methods for use in assessing passenger/crew ride comfort within helicopters. Included are results quantifying 35 helicopter pilots' discomfort responses to helicopter interior noise and vibration typical of routine flights, assessment of various ride quality metrics including the NASA ride comfort model, and examination of possible criteria approaches. Results of the study indicated that crew discomfort results from a complex interaction between vibration and interior noise. Overall measures such as weighted or unweighted root-mean-square acceleration level and A-weighted noise level were not good predictors of discomfort. Accurate prediction required a metric incorporating the interactive efefcts of both noise and vibration. The best metric for predicting crew comfort to the combined noise and vibration environment was the NASA discomfort index. (Author).
Author: Roger C. Strawn Publisher: ISBN: Category : Fluid dynamics Languages : en Pages : 18
Book Description
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."
Author: Gareth D. Padfield Publisher: John Wiley & Sons ISBN: 111940102X Category : Technology & Engineering Languages : en Pages : 856
Book Description
The Book The behaviour of helicopters and tiltrotor aircraft is so complex that understanding the physical mechanisms at work in trim, stability and response, and thus the prediction of Flying Qualities, requires a framework of analytical and numerical modelling and simulation. Good Flying Qualities are vital for ensuring that mission performance is achievable with safety and, in the first and second editions of Helicopter Flight Dynamics, a comprehensive treatment of design criteria was presented, relating to both normal and degraded Flying Qualities. Fully embracing the consequences of Degraded Flying Qualities during the design phase will contribute positively to safety. In this third edition, two new Chapters are included. Chapter 9 takes the reader on a journey from the origins of the story of Flying Qualities, tracing key contributions to the developing maturity and to the current position. Chapter 10 provides a comprehensive treatment of the Flight Dynamics of tiltrotor aircraft; informed by research activities and the limited data on operational aircraft. Many of the unique behavioural characteristics of tiltrotors are revealed for the first time in this book. The accurate prediction and assessment of Flying Qualities draws on the modelling and simulation discipline on the one hand and testing practice on the other. Checking predictions in flight requires clearly defined mission tasks, derived from realistic performance requirements. High fidelity simulations also form the basis for the design of stability and control augmentation systems, essential for conferring Level 1 Flying Qualities. The integrated description of flight dynamic modelling, simulation and flying qualities of rotorcraft forms the subject of this book, which will be of interest to engineers practising and honing their skills in research laboratories, academia and manufacturing industries, test pilots and flight test engineers, and as a reference for graduate and postgraduate students in aerospace engineering.
Author: Lauren Weist
Author: Lauren Weist
Author: 
Author: F. H. Schmitz
Author: 
Author: Damaris Zachos
Author: Willca Villafana
Author: J. D. Leatherwood
Author: D.S. Weir
Author: Roger C. Strawn
Author: Gareth D. Padfield