This thesis describes an experimental investigation of high frequency acoustic wave scattering from turbulent premixed flames. The objective of this work was to characterize the scattered incoherent acoustic field and determine its parametric dependence on frequency, flame brush thickness, incident and measurement angles, mean velocity and flame speed. The experimental facility consists of a slot burner with a flat flame sheet that is approximately 15 cm wide and 12 cm tall. The baseline cold flow characteristics and flame sheet statistics were extensively characterized. Studies were performed over a wide range of frequencies (1-24 kHz) in order to characterize the role of the incident acoustic wave length. The spectrum of the scattered acoustic field showed distinct incoherent spectral sidebands on either side of the driving frequency. The scattered incoherent field was characterized in terms of the incoherent field strength and spectral bandwidth and related to the theoretical predictions. The role of the flame front wrinkling scale, i.e., flame brush thickness, was also studied. Flame brush thickness was varied independent of the mean velocity and flame speed by using a variable turbulence generator. Results are reported for five flame brush thickness cases, ranging from 1.2 mm to 5.2 mm. Some dependence of scattered field characteristics on flame brush thickness was observed, but the magnitude of the effect was much smaller than expected from theoretical considerations. The spatial dependence of the scattered field was investigated by measuring the scattered field at four measurement angles and exciting the flame at four incident angles. Theory predicts that these variations influence the spatial scale of the acoustic wave normal to the flame, a result confirmed by the measurements. Measurements were performed for multiple combinations of mean velocities and flame speeds. The scattered field was observed to depend strongly on the flame speed. Further analysis suggested that the change in orientation angle distribution with flame speed had a large influence on the scattered field. The scattered field characteristics did not show any appreciable change with mean velocity. This result was expected since flame brush thickness characteristics themselves exhibit a weak velocity dependence.

A new approach was developed to determine the operational stability margin of a laboratory scale combustor. Applying modern and robust techniques and tools from Dynamical System Theory, the approach was based on three basic steps. In the first step, a gray-box thermoacoustical model for the combustor was derived. The second step consisted in applying System Identification techniques to experimental data in order to validate the model and estimate its parameters. The application of these techniques to experimental data under different operating conditions allowed us to determine the functional dependence of the model parameters upon changes in an experimental control parameter. Finally, the third step consisted in using that functional dependence to predict the response of the system at different operating conditions and, ultimately, estimate its operational stability margin. The results indicated that a low-order stochastic non-linear model, including two excited modes, has been identified and the combustor operational stability margin could be estimated by applying a continuation method.

Supercavitating torpedoes pose new threats to submarines, surface ships, and shore targets whose current countermeasures are inadequate against this technology. These torpedoes have the advantage over their predecessors and companion weapons of dramatically increased speed, which reduces the reaction time available for deploying a countermeasure heightening the threat to their intended target. Proliferation of supercavitating torpedoes has motivated research on countermeasures against them as well as on the fluid phenomenon which makes them possible. The goal of this research was to investigate an envisaged countermeasure; an acoustic field capable of slowing or diverting the weapon by disrupting the cavitation envelope. The research focused on the interactions between high-level sound signals and a supercavity produced by a small free-flying projectile. In order to conduct this study it was necessary to achieve three preliminary accomplishments involving the design of: 1) experimental apparatus that allowed for the study of a small-scale supercavitating projectile in the laboratory environment; 2) apparatus and software for measuring and recording information about projectile dynamics and supercavity geometry; and 3) an acoustic array and power source capable of focusing the desired sound signal in the path of the supercavitating object. Positive results have been found which show that the accuracy of a supercavitating projectile can indeed be adversely affected by the sound signal. This research concludes with results that indicate that it is acoustic cavitation in the medium surrounding the supercavity that is responsible for the reduced accuracy. A hypothesis has been presented addressing the means by which the acoustic cavitation could cause this effect. Additionally, corrugations on the cavity/water interface imposed by the pressure signal have been observed and characterized.

Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 236-258.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 7, 2008) Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Mechanical Engineering Department, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2005. / Anderson, David, Committee Chair ; Barnwell-III, Thomas, Committee Member ; Clements, Mark, Committee Member ; Truong, Kwan, Committee Member ; Basu, Saugata, Committee Member. Vita. Includes bibliographical references.

In the context of limited availability of fossil fuel and the impact of fossil-based energy utilization to the environment, novel porous materials have been extensively investigated for applications in environmentally friendly energy generation and storage. This thesis describes work wherein porous carbons and mesoporous silica materials have been systematically studied to include new synthesis strategies, material characterization. Two main themes of this thesis are, firstly, to investigate how porosity affects the utilization of activated carbons in energy storage and gas adsorption, and secondly, explore the stabilization of mesoporous silica materials. Chapter 1 discusses structures and classifications of pores. Porous carbons and mesoporous silica materials are introduced including the fundamental properties, preparation and important applications of the materials. Chapter 2 gives the basics of techniques used for characterization of the porous materials fabricated in this work. Gas sorption techniques applied for hydrogen storage and carbon dioxide uptake are introduced. The chapter also presents the electrochemistry and electrochemical methods used in this work. Chapter 3 briefly describes the preparation of highly porous carbons from lignin via hydrothermal carbonisation followed by chemical activation using KOH as activating agent. The work evidences the influence of activation temperature and KOH/carbon weight ratio on the structure of activated carbon and the performance of the gas storage capacity. Activation at KOH/carbon ratio of 2 generates highly microporous carbons which exhibit excellent CO2 uptake capacity; up to 4.6 mmol/g at 1 bar and 25 oC. Activation at KOH/carbon ratio of 4 can, on the other hand, generate lignin-derived carbons with ultrahigh porosity. These higher surface area lignin-derived carbons exhibit attractive hydrogen uptake capacity of up to 6.2 wt% at -196 oC and 20 bar. Chapter 4 is devoted to the use of lignin-derived activated carbons (LAC) as electrode materials for supercapacitors in aqueous and ionic liquid electrolytes. The study shows several factors affecting the electrochemical performance of carbon electrodes. It is demonstrated that a high surface area carbon (designated as LAC4800) electrode in 2 M H2SO4 exhibits a high capacitance value of 223 F/g or surface capacitance of 11.49 µF/cm2 and good cycling stability over 1000 cycles. The LAC electrodes also showed attractive capacitive performance with 175 F/g (6.92 µF/cm2) and the energy density can be enhanced in ionic electrolytes to reach 97.2 Wh/kg and power density of 2.0 kW/kg at 0.5 A/g for sample LAC4800 in BMImBF4 electrolyte. Chapter 5, regarding non-carbon materials, new forms of MCM-41 type silica mesostructures have been prepared by increasing the applied crystallization temperature to between 150 and 190 oC. The high temperature crystallisation resulted in enlargement of pore size and generated thicker pore walls. The sample prepared at 190 oC shows exceptional hydrothermal and thermal stability, even retaining long-range mesostructural ordering after refluxing in boiling water for 24 h or heating at 1000 oC for 4 h, which is unprecedented for pure silica MCM-41 materials. Finally, the conclusions for the thesis including the suggestion for future work are proposed in Chapter 6.

This thesis investigates the feasibility of using gestures as a means of control for localizing three dimensional (3D) sound sources in a distributed immersive audio system. A prototype system was implemented and tested which uses state of the art technology to achieve the stated goals. A Windows Kinect is used for gesture recognition which translates human gestures into control messages by the prototype system, which in turn performs actions based on the recognized gestures. The term distributed in the context of this system refers to the audio processing capacity. The prototype system partitions and allocates the processing load between a number of endpoints. The reallocated processing load consists of the mixing of audio samples according to a specification. The endpoints used in this research are XMOS AVB endpoints. The firmware on these endpoints were modified to include the audio mixing capability which was controlled by a state of the art audio distribution networking standard, Ethernet AVB. The hardware used for the implementation of the prototype system is relatively cost efficient in comparison to professional audio hardware, and is also commercially available for end users. the successful implementation and results from user testing of the prototype system demonstrates how it is a feasible option for recording the localization of a sound source. The ability to partition the processing provides a modular approach to building immersive sound systems. This removes the constraint of a centralized mixing console with a predetermined speaker configuration.

Le confort acoustique des passagers à l’intérieur d’un véhicule est fonction des équipements embarqués notamment le Système de Ventilation d’Air (SVA). Un SVA est un système complexe et compact, composé de plusieurs éléments. L’interaction de l’écoulement d’air avec ces éléments est un facteur influant sur les phénomènes acoustiques générés. Le projet CEVAS (Conception d’Eléments de Ventilation d’Air Silencieux), piloté par l’équipementier Valeo, a pour ambition de développer un outil numérique d’aide à la conception des SVA. Dans le cadre de projet, un banc d’essai a été développé à l’UTC en coopération avec Valeo afin de caractériser par mesures acoustique et aéraulique les composants d’un SVA dans les mêmes conditions de fonctionnement que sur véhicule. L’instrumentation acoustique de ce banc permet la caractérisation multimodale des propriétés acoustiques passives et actives de l’élément testé. Dans un premier lieu, la composante passive, représentée par la matrice de diffusion, est mesurée par la méthode multi-sources. Par la suite, la composante active, représentative de l’interaction écoulement objet, est déduite des pressions modales rayonnées en amont et en aval. Les démarches de mesure et de post-traitement sont appliquées pour des éléments académiques et des composants industriels : diaphragme, association de deux diaphragmes, volets et associations volet et mur. / Passenger’s thermal comfort inside car cabin is mainly provided by the heating ventilation and air conditioning system (HVAC). The main part of HVAC modules is placed under the dash board. An HVAC module is a compact system composed of various elements which are subject to airflow. The interaction between airflow and these in-duct elements generates noise inside car cabin. Furthermore, the blower used to blow air inside the cabin must overcome the pressure generated by HVAC elements. Noise is created and its level is linked to flow and pressure. HVAC noise is an important issue for car makers and automotive suppliers wishing to reach passenger’s satisfaction. Furthermore, thermal-engine cars are more and more silent. Also hybrid and electric car sells are expanding around the world. HVAC noise became a main issue for automotive actors. Under CEVAS project, Valeo is aiming to develop a prediction tool to design HVAC systems providing sound quality data. Within CEVAS project the UTC is in charge of performing measurements on academic elements and industrial HVAC components : diaphragm, flaps,…