Accurate methods for glottal feature extraction include the use of high-speed video imaging (HSVI). There have been previous attempts to extract these features with the acoustic recording. However, none of these methods compare their results with an objective method, such as HSVI. This thesis tests these acoustic methods against a large diverse population of 46 subjects. Two previously studied acoustic methods, as well as one introduced in this thesis, were compared against two video methods, area and displacement for open quotient (OQ) estimation. The area comparison proved to be somewhat ambiguous and challenging due to thresholding effects. The displacement comparison, which is based on glottal edge tracking, proved to be a more robust comparison method than the area. The first acoustic methods OQ estimate had a relatively small average error of 8.90% and the second method had a relatively large average error of -59.05% compared to the displacement OQ. The newly proposed method had a relatively small error of -13.75% when compared to the displacements OQ. There was some success even though there was relatively high error with the acoustic methods, however, they may be utilized to augment the features collected by HSVI for a more accurate glottal feature estimation.

Fluidization of a granular assembly of solid particles is a process where particles are suspended in a fluid by the upward flow of fluid through the bed. This process is important in industry as it has a wide range of applications due to the high mixing and mass transfer rates present as a result of the rapid movement of particles which occurs in the bed. The dynamics of fluidization is heavily dependent on the particle scale physics and the forces acting at a particle level. For particles with sizes and densities less than 100μm and 103 kg/m3, the importance of interparticle forces such as cohesion to the fluidization phenomena observed increases compared to larger particles where phenomena observed are more dependent on hydrodynamic forces. These smaller sized particles are increasingly in high demand in industrial processes due to the increasing surface area per unit volume obtained by decreasing the particle size. Decreasing particle however leads to an increase in the impact of cohesive interparticle forces present between particles thus altering fluidization phenomena. It is thus necessary to get a greater understanding of how these cohesive forces alter fluidization behaviour both at the particle and also at the bulk scale. This work begins with an experimental study of a fluidized bed using high speed imaging. The applicability of particle image velocimetry for a dense bed is examined with verification and validation studies showing that particle image velocimetry is able to accurately capture averaged velocity profiles for particles at the front wall. A digital image analysis algorithm which is capable of accurately extracting particle solid fraction data for a dense bed at non-optimum lighting conditions was also developed. Together both experimental techniques were used to extract averaged particle mass flux data capable of accurately capturing and probing fluidization phenomena for a dense fluidized bed. This simulation studies carried out for this work looks to examine the impact of cohesive forces introduced using a van der waal cohesion model on phenomena observed at different length scales using DEM-CFD simulations. Numerical simulations were run for Geldart A sized particles at different cohesion levels represented by the bond number and at different inlet gas velocities encompassing the different regimes fluidization regimes present. A stress analysis was used to examine the mechanical state of the expanded bed at different cohesion levels with the vertical component of the total stress showing negative tensile stresses observed at the center of the bed. Further analysis of the contact and cohesive components of the stress together with a kcore and microstructural analysis focusing on the solid fraction and coordination number profiles indicated that this negative total stress was caused by a decrease in the contact stress due to breakage of mechanical contacts as cohesive forces are introduced and increased. A pressure overshoot analysis was also conducted with the magnitude of the overshoot in pressure seen during the pressure drop analysis of a cohesive bed shown to be of equivalent magnitude to the gradient of the total negative stress profile. The in-homogeneous nature of the bed was probed with the focus on how introducing cohesion levels increase the degree of inhomogeneity present in the expanded bed and how local mesoscopic structures change with cohesion and gas velocity. It was shown that increasing cohesion increases the degree of inhomogeneity in the bed as well as increasing the degree of clustering between particles. A majority of particles were shown to be present in a single macroscopic cluster in the mechanical network with distinct local mesoscopic structures forming within the macroscopic cluster. The cohesive bed also expanded as distinct dense regions with low mechanical contact zones in between these regions. A macroscopic cluster analysis showed that the majority of particles are in strong enduring mechanical and cohesive contact. Increasing cohesive forces were also shown to not only create a cohesive support network around the mechanical network but also strengthen the mechanical contact network as well. The significance of the strong and weak mechanical and cohesive forces on fluidization phenomena was also examined with analysis showing that the weak mechanical forces act to support the weak mechanical forces. The cohesive force network however was non coherent with strong forces significantly greater than weak forces. Fluidization phenomena was shown to be driven by the magnitude of the strong cohesive forces set by the minimum particle cutoff distance. This also called into question the significance of the cohesive coordination number which is dependent on the maximum cohesive cutoff. The value of the maximum cutoff was shown to be less significant as no significant changes were observed in the stress and microstructure data as the maximum cutoff was altered. Simulations with different ratios of cohesive and non cohesive particles were also undertaken and showed that a disruption in the cohesive force network leads to changes in the stress state and microstructure of the bed thus changing the fluidization phenomena observed at all length scales. The nature of the strong cohesive force network thus drives fluidization phenomena seen in the bed.

The impact of a spherical object onto a surface of a liquid, solid or granular material, is a configuration which occurs in numerous industrial and natural phenomena. The resulting dynamics can produce complex outcomes and often occur on very short time-scales. Their study thereby requires high-speed video imaging, as is done herein. This three-part dissertation investigates widely disparate but kindred impact configurations, where the impacting object is a solid steel sphere, or a molten metal droplet. The substrate, on the other hand, is either granular material, a liquid, or solid ice. Therefore both fluid mechanics and thermodynamics play a key role in some of these dynamics. Part I, investigates the penetration depth of a steel sphere which impacts onto a granular bed containing a mixture of grains of two different sizes. The addition of smaller grains within a bed of larger grains can promote a “lubrication” effect and deeper penetration of the sphere. However, there needs to be enough mass fraction of the smaller grains so that they get lodged between the larger grains and are not simply like isolated rattlers inside the voids between the larger grains. This lubrication occurs even though the addition of the small grains increases the overall packing fraction of the bed. We compare the enhanced penetration for the mixtures to a simple interpolative model based on the results for monodispersed media of the constitutive sizes. The strongest lubrication is observed for large irregular shaped Ottawa sand grains, which are seeded with small spherical glass beads. Part II, tackles the topic of a molten metal drop impacting onto a pool of water. When the drop temperature is far above the boiling temperature of water, a continuous vapor layer can form at the interface between the metal and water, in what is called the Leidenfrost phenomenon. This vapor layer can become unstable forming what is called a vapor explosion, which can break up the molten metal drop. We study the details of these explosions and characterize the metal debris. We contrast the results for two different metals, i.e. tin and a special metal alloy called Field’s metal. For tin the drop solidifies and forms a porous foam-like solid, whereas the Field’s metal breaks up into a multitude of spherical beads, with a range of sizes as small as a few microns. We attribute this difference to the much lower melting point of the Field’s metal, which is only 60oC, compared to 230oC for the tin. This allows more fragmentation of the Field’s metal drop before it solidifies. When the temperature of the impacting metal is increased, high-speed imaging reveals a sequence of up to three vapor explosions, each of increasing intensity. We measure the acceleration of the vapor interface and compare the size-distribution of the microbeads to the fastest growing instability mode of the corresponding Rayleigh-Taylor instability. Part III, investigates the coefficient of restitution when a steel sphere impacts on an ice surface. As observed in earlier studies the restitution coefficient is largest for the smallest impact velocities, where the surface is not greatly fragmented. Our focus is on greatly heating the sphere up to 400oC to investigate how the thermal load affects the short term interaction of the sphere with the ice. We see a clear trend where hotter spheres rebound less than cold spheres. We also track the speed of ice-fragments ejected during the earliest stages of the impact.

Drop impacts are present in our everyday lives, from showering and washing the dishes to inkjet printing and many industrial processes, such as spray coatings and spray cooling. In many of these applications it may be undesirable to have air entrained within the drop when it impacts a surface. As a drop approaches a surface, the gas beneath the drop is unable to fully escape resulting in a rising pressure which becomes sufficient to form a dimple in the bottom center of the drop. Therefore, when the drop makes contact with the surface, it is around the perimeter of this dimple, thus entrapping a disc of air which contracts into a minute bubble. In this dissertation, we study the very early time dynamics of the formation of the central air disc under a variety of circumstances using ultra-high-speed interferometry at rates up to 5 million frames per second. We show the effects of the liquid viscosity for viscosities spanning 7 orders of magnitude, for impacts of drops onto solid surfaces or a film of the same liquid. We find that the size of the air disc is weakly dependent on the drop viscosity to the -1/9 power. We also explore the extended gliding of the drop on a less than 160 nm thick film of air. For impacts onto a solid surface, this gliding layer is rupture in multiple random locations and each localized contact wets the surface at extreme rates compared with the expected viscous-capillary velocity. For impacts onto liquid films, the localized contacts are rarely observed and the gliding layer ruptures at a uniform location. The central bubble contracts much faster than expected in this case as well. Furthermore, we study the effects of reducing the ambient air pressure discovering a compressible and rarified-gas regime wherein the drop makes a double contact with the surface. Lastly, we study the effects of nano-scale surface roughness on the central bubble and the formation of thick bands of microbubbles around the periphery of the air disc.

Un moyen d'accroître l'efficacité et de réduire la pollution dans les domaines du transport et de l'énergie consiste à concevoir des injecteurs de carburant produisant une meilleure atomisation. Au cours de cette thèse, des expériences ont été effectuées sur un injecteur airblast souvent utilisé dans les turbines à gaz. Pour réaliser ces expérimentations, un dispositif modèle en configuration annulaire a été créé afin d'étudier le cisaillement d'un film d'eau soumis à un écoulement d'air interne à forte vitesse. La technique d'imagerie rapide par ombroscopie a été utilisée pour analyser le développement du film liquide (fréquence et célérité des ondes) et l'atomisation de la nappe en sortie d'injecteur (modes de rupture). La modification des paramètres d'injection (vitesse des écoulements) a révélé un lien entre la topologie du film liquide et le régime d'atomisation primaire. Finalement, à titre exploratoire, l'influence de la géométrie de l'injecteur (longueur de préfilm) sur le mode d'atomisation primaire a également été mise en évidence / One way to increase efficiency and reduce pollution in the transportation and energy domain is designing fuel injectors with better atomization. In this thesis, experiments were performed on a prefilming airblast atomizer often used in gas turbines. For this purpose, a model device with a cylindrical configuration was created to study the shearing of a film of water subjected to an internal high speed air flow. High speed shadowgraphy technique was used to analyse the development of the liquid film (frequency and wave celerity) and the atomization of the sheet at the injector outlet (breakup mode). The modification of the injection parameters (velocity of flows) revealed a link between the topology of the liquid film and the primary atomization regime. Finally,the influence of the geometry of the injector (prefilming length) about the mode of primary atomization was also highlighted with an exploratory study

We present two distinct projects in this article. In the first project, an experiment aiming to quantify the impacts of material acoustic impedance and thickness on single laser-induced cavitation bubble dynamics with measurements of exerted pressure on a specific material in order to identify the primary sources most responsible for material damages is presented in this article. Two types of major pressure sources have been identified. For bubble collapsing near a rigid wall, when standoff ratio γ < 0.6, the ring collapse is the most prominent pressure source. The jet takes the strongest effects at γ = 1.12. The pressure is minimal at γ = 0.913. After the first jet impingement, a second ring collapse will follow and input the maximum pressure to the wall. By further increasing γ, a similar pressure profile of the second collapse to the first collapse is achieved, during which the pressure for the second collapse is minimal at γ = 1.41 and for the jet is maximum at γ = 1.79. Compared with the maximum pressure dealt by the first jet, the second ring collapse and jet are increasing much faster with the bubble size and eventually overwhelm the first jet. However, the first ring collapse is still the most dominant pressure source responsible for material damages. For wall featuring smaller acoustic impedance or thickness that cannot be approximated to a rigid body, the ring collapse and jet occur at smaller standoff ratios. The cavity shrinking rate suggests the maximum pressure exerted on the wall at applicable standoff ratios should be smaller than that on a rigid wall. In the second project, a comprehensive collection of dynamics of one and two laser-induced cavitation bubbles collapsing near different boundaries is presented in this article by measuring the velocity fields using particle image velocimetry (PIV) techniques. Cases include a single bubble collapsing near the hard, medium, and soft walls characterized by acoustic impedance, free collapse of two bubbles, and two bubbles collapsing near the hard and soft walls. We implemented the most significant velocity and top velocity regions derived from each velocity field to analyze the features of these cases. Before converging to free collapse, the bubble near the hard wall experienced a significant velocity decrease before collapse, the bubble near the medium wall was severely damped at a specific standoff distance, and the bubble near the soft wall collapsed much earlier and preserved a linear velocity region at low speed. Free collapse of two same bubbles underwent a decrease of acceleration before collapse. Decreasing the size of one bubble caused a jet in the other. With the presence of a hard wall near two bubbles, the bubble closer to it may be stretched to a cavity with a high aspect ratio, leading to very mild collapse. With a bigger bubble between a smaller one and the soft wall, the merging cavity may suppress the tendency of jet formation, making the velocity stay at low levels throughout the lifetime. For configurations regarding single bubbles collapsing near a wall and free collapse of two same bubbles, we performed data scaling to study the velocity variations for different bubble sizes by controlling the standoff ratios and assessed the data quality aided by curving fitting and statistics. Results indicated measured velocity regarding a single bubble collapsing near the wall over its diameter remained the same given a standoff ratio, while measured velocity did not change given a standoff ratio for free collapse of two same bubbles within the scope of the experiment. In addition, we detailed the experimental setup and water treatment for better signal-to-noise ratios as well as validated the system from both the PIV and high speed imaging approaches using free collapse of a single bubble to ensure the reliability of this experiment. / Doctor of Philosophy / The phenomenon of cavitation extensively exists. These small and transient bubbles are observed typically in fast moving fluids, e.g., shaking a bottle of water. Each bubble experi- ences a process of growth, collapse, rebound, and collapse again before it is gone. Although the bubble is tiny, the collapse of a bubble releases considerable pressure, which is intense enough to damage nearby objects over time. This interaction between bubbles and objects depends highly on the types of objects such as the materials and thickness. To study how the bubble behaves near a wall (object) and explain how the wall is damaged, we present two projects in this article. In the first project, we created a bubble near a wall at differ- ent bubble-to-wall distances and tracked how the bubble changed its shape until collapse with a fast speed camera. This work was repeated for multiple different wall materials and thickness. We then measured the pressure exerted by a bubble at a series of different bubble-to-wall distances on a specific wall equipped with a sensor. By comparing and sum- marizing results from both the bubble shape changes near different walls and the pressure measurement, we found the relationship between the magnitude of pressure and the distance between the bubble and the wall. In the second project, we implemented the particle image velocimetry (PIV) techniques to measure the velocity fields. By feeding particles into the fluid, PIV tracks the location differences of particles in two subsequent frames to determine the velocity of every point. Based on that, we obtained a collection of velocity fields of interaction between single bubbles and walls, two bubbles, and two bubbles and walls.

Violent crimes involving bloodshed may result in the formation of a number of blood drops that move through air and impact onto a surface producing a bloodstain pattern. Bloodstain Pattern Analysis (BPA), the analysis of the position, distribution, size and morphology of the stains within the pattern present at a crime scene, may provide information about the events that gave rise to the bloodshed. The location of blood origin, i.e. victim’s position at the moment of wounding and (or) wound location, determination is of major interest to BPA. This study investigated the dynamics of formation and flight of blood drops commonly found at a crime scene (so-called passive, cast-off, impact and gunshot drops) with the aim to facilitate blood origin determination. Features of blood drop formation at passive dripping with correlation to dripping surface characteristics were studied experimentally. A numerical scheme for accurate blood drop flight characteristics modelling, including oscillations, deformation and disintegration, was developed and validated against a number of analytical and experimental cases with special attention to the passive blood drop oscillations and ultimate deformation at terminal velocity, cast-off and impact blood drop deformation and breakup features. This provided an efficient and accurate method for typical blood drop flight reconstruction from the blood origin to impact as well as from the bloodstain location to the possible blood origin. Factors affecting blood drop trajectory and blood origin estimation were studied using the developed scheme.

Three methods were developed to better understand and characterize the near-field dynamic processes of rotary bell atomization. The methods were developed with the goal of possible integration into industry to identify equipment changes through changes in the primary atomization of the bell. The first technique utilized high-speed imaging to capture qualitative ligament breakup and, in combination with a developed image processing technique and PIV software, was able to gain statistical size and velocity information about both ligaments and droplets in the image data. A second technique, using an Nd:YAG laser with an optical filter, was used to capture size statistics at even higher rotational speeds than the first technique, and was utilized to find differences between serrated and unserrated bell ligament and droplet data. The final technique was incorporating proper orthogonal decomposition (POD) into image data of a side-profile view of a damaged and undamaged bell during operation. This was done to capture differences between the data sets to come up with a characterization for identifying if a bell is damaged or not for future industrial integration.

Sootblowing is a process in which supersonic steam jets are used to periodically blast deposits off heat transfer tubes in kraft recovery boilers. However, sootblowing significantly consumes the valuable high pressure steam generated by the boiler, hence it should be optimized. A recovery boiler consists of three convective sections - superheater, generating bank and economizer. The tube arrangement in these sections, particularly the tube spacing is different from each other. Moreover, tubes in an economizer are finned. A sootblower jet will interact differently with these tube arrangements, potentially affecting its strength, and hence deposit removal capability. The objective of this work was to characterize jet/tube interaction in the three sections of a recovery boiler. Lab-scale experiments were conducted in which these interactions were visualized using the schlieren technique coupled with high-speed video, and were quantified by pitot pressure measurements. This work is the first to visualize the interactions. The offset between the jet and tube centrelines, the nozzle exit diameter relative to the tube diameter, and the distance between the nozzle and tube were varied to examine their effects on jet/tube interaction. Results showed that due to the very low spreading rate of a supersonic jet, a jet (primary jet) stops interacting with a superheater platen when the jet is only a small distance away from it. When the jet impinges on a tube, the jet deflects at an angle, giving rise to a weaker ‘secondary’ jet. Due to the large inter-platen spacing, a secondary jet has an insignificant impact in a superheater. In a generating bank, the primary jet weakens between the closely spaced tubes due to increased mixing. However, a secondary jet impinges on the adjacent tubes exerting a high impact pressure on those tubes. The primary jet also weakens between finned economizer tubes, but remains stronger for a greater distance than in a generating bank. As in the case inside a generating bank, a secondary jet also impinges on adjacent rows of tubes in an economizer. The results imply that in a superheater, a sootblower jet must be directed close to the platens to yield useful jet/deposit interactions, and to avoid wasting steam by blowing between the platens. In a generating bank, deposits beyond the first few tubes of a row experience a weaker sootblower jet, and thus may not be removed effectively. However, secondary jets may contribute to removing deposits from the first few adjacent tubes. They may also induce erosion-corrosion of those tubes. Secondary jets may also help remove deposits from adjacent rows in a finned tube economizer. In an economizer, the strength and hence, the deposit removal capability of a sootblower jet diminish only slightly beyond the supersonic portion of the jet. A mathematical model was also developed to determine the feasibility of using inclined sootblower nozzles in recovery boiler superheaters, and suggests that it may be possible to clean superheater platens more effectively with slightly inclined nozzles.

Sootblowing is a process in which supersonic steam jets are used to periodically blast deposits off heat transfer tubes in kraft recovery boilers. However, sootblowing significantly consumes the valuable high pressure steam generated by the boiler, hence it should be optimized. A recovery boiler consists of three convective sections - superheater, generating bank and economizer. The tube arrangement in these sections, particularly the tube spacing is different from each other. Moreover, tubes in an economizer are finned. A sootblower jet will interact differently with these tube arrangements, potentially affecting its strength, and hence deposit removal capability. The objective of this work was to characterize jet/tube interaction in the three sections of a recovery boiler. Lab-scale experiments were conducted in which these interactions were visualized using the schlieren technique coupled with high-speed video, and were quantified by pitot pressure measurements. This work is the first to visualize the interactions. The offset between the jet and tube centrelines, the nozzle exit diameter relative to the tube diameter, and the distance between the nozzle and tube were varied to examine their effects on jet/tube interaction. Results showed that due to the very low spreading rate of a supersonic jet, a jet (primary jet) stops interacting with a superheater platen when the jet is only a small distance away from it. When the jet impinges on a tube, the jet deflects at an angle, giving rise to a weaker ‘secondary’ jet. Due to the large inter-platen spacing, a secondary jet has an insignificant impact in a superheater. In a generating bank, the primary jet weakens between the closely spaced tubes due to increased mixing. However, a secondary jet impinges on the adjacent tubes exerting a high impact pressure on those tubes. The primary jet also weakens between finned economizer tubes, but remains stronger for a greater distance than in a generating bank. As in the case inside a generating bank, a secondary jet also impinges on adjacent rows of tubes in an economizer. The results imply that in a superheater, a sootblower jet must be directed close to the platens to yield useful jet/deposit interactions, and to avoid wasting steam by blowing between the platens. In a generating bank, deposits beyond the first few tubes of a row experience a weaker sootblower jet, and thus may not be removed effectively. However, secondary jets may contribute to removing deposits from the first few adjacent tubes. They may also induce erosion-corrosion of those tubes. Secondary jets may also help remove deposits from adjacent rows in a finned tube economizer. In an economizer, the strength and hence, the deposit removal capability of a sootblower jet diminish only slightly beyond the supersonic portion of the jet. A mathematical model was also developed to determine the feasibility of using inclined sootblower nozzles in recovery boiler superheaters, and suggests that it may be possible to clean superheater platens more effectively with slightly inclined nozzles.