Physically derived sound synthesis model of a propeller

© 2017 Copyright held by the owner/author(s). A real-time sound synthesis model for propeller sounds is presented. Equations obtained from fluid dynamics and aerodynamics research are utilised to produce authentic propeller-powered aircraft sounds. The result is a physical model in which the geometries of the objects involved are used in sound synthesis calculations. The model operates in real-time making it ideal for integration within a game or virtual reality environment. Comparison with real propeller-powered aircraft sounds indicates that some aspects of real recordings are not replicated by our model. Listening tests suggest that our model performs as well as another synthesis method but is not as plausible as a real recording

Auralization of Air Vehicle Noise for Community Noise Assessment

This paper serves as an introduction to air vehicle noise auralization and documents the current state-of-the-art. Auralization of flyover noise considers the source, path, and receiver as part of a time marching simulation. Two approaches are offered; a time domain approach performs synthesis followed by propagation, while a frequency domain approach performs propagation followed by synthesis. Source noise description methods are offered for isolated and installed propulsion system and airframe noise sources for a wide range of air vehicles. Methods for synthesis of broadband, discrete tones, steady and unsteady periodic, and a periodic sources are presented, and propagation methods and receiver considerations are discussed. Auralizations applied to vehicles ranging from large transport aircraft to small unmanned aerial systems demonstrate current capabilities

The steady-state structure of accretion discs in central magnetic fields

We develop a new analytic solution for the steady-state structure of a thin accretion disc under the influence of a magnetic field that is anchored to the central star. The solution takes a form similar to that of Shakura and Sunyaev and tends to their solution as the magnetic moment of the star tends to zero. As well as the Kramer's law case, we obtain a solution for a general opacity. The effects of varying the mass transfer rate, spin period and magnetic field of the star as well as the opacity model applied to the disc are explored for a range of objects. The solution depends on the position of the magnetic truncation radius. We propose a new approach for the identification of the truncation radius and present an analytic expression for its position.Comment: 11 pages, 7 figures, accepted by MNRA

Flight Investigation of Gyroplane Longitudinal Flight Dynamics

This Paper presents an analysis of test data recorded during flight trials of a gyroplane. This class of rotarywing aircraft has found limited application in areas other than sport or recreational flying. However, the accident rate is such that a study of the configuration's stability and control characteristics is timely, and in addition substantive data is required for a new airworthiness and design standard that is under development. The Paper presents a unique coupling of established parameter estimation techniques with data from a class of aircraft that has received no attention in the contemporary literature. As a consequence, the Paper helps to consolidate the status of system identification as a powerful tool in the analysis of rotorcraft engineering problems. It is concluded that robust estimates of the longitudinal stability and control derivatives have been identified, indicating benign and "classical" longitudinal stability and control characteristics. However, unlike most helicopters, the rotorspeed degree of freedom must be included in the model structure

Computational aerodynamics for open rotor tip vortex interaction noise prediction

Open rotor engines can provide fuel savings of up to twenty seven percent compared to a modern high bypass turbofan engine. They were subject to intense research in the 1980s in response to the 1973 oil crisis. They have come back into consideration to combat the strict environmental regulations currently imposed on the aviation industry and to meet the ACARE 2020 requirements. Recent large scale European projects such as DREAM and Clean Sky have included signi cant research on the open rotor since their comeback. Their major drawback is the noise levels generated when the wake and tip vortices of the front rotor interact with the aft rotor. The noise generated from these interactions is highly tonal which makes the open rotor prohibitively noisy. The Unducted Fan (UDF) demonstrator engine was built in the 1980s by General Electric in collaboration with NASA. During the design phase of this project a computer code named CRPFAN was developed to predict the noise of open rotors. CRPFAN is used as a representative preliminary design noise prediction tool and was the only representative tool available to the author at the time of the project. Included in CRPFAN is a vortex model which relies heavily on outdated empirical re- lations. There is currently a better knowledge of tip vortex properties relative to when the code was created. However, there has been no signi cant study on how the speci c parameters of a tip vortex relate to the noise of an open rotor or how to more accurately predict the tip vortex parameters, which is what this project aims to do. The rst part of the project developed methods to quantify how the tip vortex param- eters relate to the noise generated by its interaction with the aft blade row. The next step was to further develop the state of the art of tip vortex models. This is done using basic analytical models integrated into CRPFAN and the use of Computational Fluid Dynamics (CFD) to model the tip vortices. CFD was used to develop bespoke tip vortex correlations which relate the tip vortex parameters to the open rotor performance parameters such as the lift, thrust and power coe cients. Correlations for the tip vortex axial velocity, trajectory, circulation and core size have been developed and integrated into CRPFAN with a detailed analysis of their performance relative to the current state of the art included. This thesis includes recommendations to improve the tip vortex models such as taking into account the spatial orientation of the vortex, inclusion of a vortex axial velocity component and how strip theory codes can under predict the noise

Applications of control theory

Applications of control theory are considered in the areas of decoupling and wake steering control of submersibles, a method of electrohydraulic conversion with no moving parts, and socio-economic system modelling

Real-Time Sound Synthesis of Aeroacoustic Sounds using Physically Derived Models

PhDThis thesis examines the use of a novel synthesis approach to reproduce aeroacoustic sound effects. This requires research into the fi eld of fluid dynamics to understand the principles which lead to a number of fundamental aeroacoustic tones. Previous research has shown that these fundamental tones can be represented by compact sound sources. Three compact sound source synthesis models are developed representing three different fundamental aeroacoustic tones, the Aeolian tone, the cavity tone and the edge tone. A number of semi-empirical equations, ones where simpli cations, generalisations or observations are considered, are found which provide mathematical relationships between the defi ning fluid dynamic parameters. Often these equations have been developed prior to computers being able to solve the complex uid dynamic equations. Frequently, these equations were developed to assist scientists and engineers reduce the aeroacoustic noise. In this instance, the equations are used to replicate the aeroacoustic sounds. The methodology of developing a compact sound source synthesis model for each of the aeroacoustic tones is presented and how this relates to the chosen noise shaping synthesis technique. Objective evaluation shows the semi-physical synthesis models perform well when compares to previously published results. Following the development of the compact sound source synthesis models, three sound e ect models are developed. These provide examples of how the synthesis models can be used to provide procedural audio sound e ects. These are swinging objects, like a sword of a club; a propeller; an Aeolian harp. Evaluation of these are carried out, with subjective evaluation indicating equal or better performance than an alternative synthesis method. The uniqueness of the implementations presented from this research is that combines the low computational requirements of a signal-based model while the parameterisation draws from equations obtained from aeroacoustic research.This work was supported by EPSRC EP/G03723X/1

Creating Real-Time Aeroacoustic Sound Effects Using Physically Informed Models

Aeroacoustics is a branch of engineering within fluid dynamics. It encompasses sounds generated by disturbances in air either by an airflow being disturbed by an object or an object moving through air. A number of fundamental sound sources exist depending on the geometry of the interacting objects and the characteristics of the flow. An example of a fundamental aeroacoustic sound source is the Aeolian tone, generated by vortex shedding as air flows around an object. A compact source model of this sound is informed from fluid dynamics principles, operating in real-time, and presenting highly relevant parameters to the user. A swinging sword, Aeolian harp, and propeller are behavior models are presented to illustrate how a taxonomy of real-time aeroacoustic sound synthesis can be achieved through physical informed modeling. Evaluation indicates that the resulting sounds are perceptually as believable as sounds produced by other synthesis methods, while objective evaluations reveal similarities and differences between our models, pre-recorded samples, and those generated by computationally complex offline methods

Fourth Aircraft Interior Noise Workshop

The fourth in a series of NASA/SAE Interior Noise Workshops was held on May 19 and 20, 1992. The theme of the workshop was new technology and applications for aircraft noise with emphasis on source noise prediction; cabin noise prediction; cabin noise control, including active and passive methods; and cabin interior noise procedures. This report is a compilation of the presentations made at the meeting which addressed the above issues

Identification of Autogyro Longitudinal Stability and Control Characteristics From Flight Test. G.U. Aero Report 9701

This Paper presents an analysis of test data recorded during flight trials of an autogyro. This class of rotary-wing aircraft has found limited application in areas other than sport or recreational flying. However, the accident rate is such that a study of the configuration's stability and control characteristics is timely, and in addition substantive data is required for a new airworthiness and design standard that is under development. The Paper presents a unique coupling of established parameter estimation techniques with data from a class of aircraft that has received no attention in the contemporary literature. As a consequence, the Paper helps to consolidate the status of system identification as a powerful tool in the analysis of rotorcraft engineering problems. It is concluded that robust estimates of the longitudinal stability and control derivatives have been identified, indicating benign and "classical" longitudinal stability and control characteristics. However, unlike most helicopters, the rotorspeed degree of freedom must be included in the model structure