Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 62 for “"Aeroacoustic"”.
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Physics-based aeroacoustic modelling of bluff-bodies
… flow solver included a high-order computational aeroacoustics code adopting large-eddy simulation, whilst a Ffowcs Williams and Hawkings solver was used for the acoustic prediction. Circular cylinders in various configurations were selected to represent basic landing gear struts and results were …
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Aeroacoustic computation of sound radiation from ducts
… research is being undertaken to understand the aeroacoustic noise source mechanisms and to accurately predict engine noise levels. High-performance computers and advanced numerical techniques are now taking an active role in this research area. In this work, a numerical solver is developed to …
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Anomaly Detection in Aeroacoustic Wind Tunnel Experiments
… array, another common system employed in aeroacoustic wind tunnels, will be analyzed similarly through evaluation of the cross-spectral matrix of microphone data, with minimal repeat measurements. A spectral projection method will be proposed that identifies unexpected acoustic source …
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2D Aeroacoustic Analysis of Flow in the Flame Trench
<p>We present here a methodology for using the commercial software ANSYSFLUENT to predict the acoustic field associated with Space-Launch System (SLS). We consider a two-dimensional model of flame deflector, and flame trench. The ANSYS code is then used to simulate the internal flow. Both the …
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Aeroacoustic control of landing gear noise using perforated fairings
A study was performed to investigate and optimize the application of perforated fairings for landing gear noise control. The sparse knowledge about this new subject has necessitated a more fundamental study involving a basic fairing-strut configuration, followed by wind tunnel tests on a simplified …
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Accurate aeroacoustic measurements in closed-section hard-walled wind tunnels
… help in the design of quieter aircraft, however aeroacoustic measurements in wind tunnels are still required. There is a growing interest in simultaneous aerodynamic and aeroacoustic measurements in hard-walled closed-section wind tunnels. The research hypothesis of this work is whether accurate …
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Aeroacoustic measurement and analysis of transient supersonic hot nozzle flows
… were tested at Boeing's steady-state low speed aeroacoustic facility for comparison to the transient shock tube noise data. The assessment establishes the uncertainty bounds on sound pressure level measurements over the range of frequency bands, nozzle pressure ratios (1.5 - 4.0), total …
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Computational aeroacoustic modelling using hybrid RANS/LES methods with modified acoustic analogies
This study considers a numerical approach to identifying noise mechanisms in tandem cylinders to understand aircraft landing gear as a primary contributor to airframe noise during approach and landing. Fluctuations in the flow properties induced by turbulence are computed as well as the …
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Development of a Plasma Spray Process Monitoring System through Aeroacoustic Signal Analysis
Plasma spray coatings are vital to the capabilities of jet engines. They allow engines to operate at combustion temperatures that would otherwise melt the superalloy components. Coatings tighten clearance between rotating components, increasing engine compression. They prevent chemical attack and …
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Aeroacoustic transfer of leading edge serrations from single aerofoils to low-pressure fan applications
Leading edge serrations are well-known for their aeroacoustic potential in reducing aerofoil-turbulence interaction noise and are also associated with certain aerodynamic advantages. To prepare leading edge serrations for industrial application, two obstacles remain to be addressed. First is a …
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Aerodynamic and aeroacoustic design of small unmanned aircraft system propellers at low Reynolds numbers.
The Small Unmanned Aircraft System (sUAS) has become an overwhelmingly important asset for military intelligence, surveillance, and reconnaissance in addition to a multitude of needs in the commercial industry. More research should investigate sUAS propulsion systems and specifically the …
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Aeroacoustic Study of a Model-Scale Landing Gear in a Semi-Anechoic Wind Tunnel
An aeroacoustic study was conducted on a 26%-scale Boeing 777 main landing gear in the Virginia Tech (VT) Anechoic Stability Wind Tunnel. The VT Anechoic Stability Wind Tunnel allowed noise measurements to be carried out using both a 63-elements microphone phased array and a linear array of 15 …
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High-Fidelity Modeling of eVTOL Rotor Unsteady Aerodynamic and Aeroacoustic Response to Time-Harmonic Gust
… This thesis investigates the aerodynamic and aeroacoustic behavior of a representative eVTOL rotor subjected to time-harmonic inflow disturbances, providing a detailed numerical framework to quantify how periodic gusts influence rotor performance, unsteady loading, and sound radiation.</p> …
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Aerodynamic and Aeroacoustic Analysis of Low Reynolds Number Propellers Using Higher-Order RANS Transition Turbulence Modeling
The advent of advanced vehicle concepts involving Urban Air Mobility (UAM) and small Unmanned Aerial Systems (sUAS) has brought about a new class of rotorcraft technology which operate predominantly in low-Reynolds ($Re$) number regimes. In such regimes, the flow experiences complex boundary layer …
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Effects of the geometric modifications on the shear layer excitation source in co-axial side branches
… markedly alter the acoustic field and the aeroacoustic sound source within deep co-axial cavities. Furthermore, it highlights how different upstream distances influence the aeroacoustic resonance of a coaxial side branch and the resultant peak acoustic pressure and the sound source term. …
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A measurement based study of the acoustics of pipe systems with flow
… of this thesis is the measurement of specific aeroacoustic properties in ducts at frequencies below the cut-on frequency of the first higher order mode. A body of measurement results are presented which highlight the effect of flow on some of the aeroacoustic characteristics in ducts as well as …
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TIME-CONSERVATIVE FINITE-VOLUME METHOD WITH LARGE-EDDY SIMULATION FOR COMPUTATIONAL AEROACOUSTICS
… Its applicability to technically relevant aeroacoustic applications is demonstrated. The time-conservative finite-volume method has unique features and advantages in comparison to traditional methods. The main objectives of this study are to develop an advanced, high-resolution, low …
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Aeroacoustics of perforated drag plates for quiet transport aircraft
… presented in this thesis focuses primarily on aeroacoustic tests and analysis of perforated drag plates. The idea behind a quiet spoiler or drag rudder is to alter the noise production mechanism by perforating the drag plates. The hypothesis is that the large length scales responsible for the …
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Fluidic ultrasound generation for nondestructive testing
… a transient triggered ultrasound pulse based on aeroacoustic sound generation mechanisms in a bistable fluidic amplifier. Little is known about its performance characteristics and suitability for nondestructive testing (NDT). The publications included in this thesis are the first to present a …
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