The condition of Gas Bubble Trauma in fish was examined in terms of specific symptoms involving bubble development in the circulatory system and buccal cavities of fish. Based on a comparison between the conditions for bubble growth in fish exposed to supersaturated water and mammals exposed to hyperbaric and hypobaric decompression a mathematical model was developed describing environmental water threshold needed to initiate bubble growth in fish. The equation development yielded expressions which related the thresholds in total dissolved gas pressure required to initiate bubble growth in the circulatory system to the partial pressure ratio of dissolved oxygen in the environmental water, oxygen uptake ratio across the gill, the size of nucleation sites in the circulatory system, the surface tension of fish blood and environmental parameters such as water temperature, depth and barometric pressure. In the case of bubble growth in the buccal cavity, environmental water thresholds were related to total gas pressure, nuclei radius, water surface tension, water temperature, depth and barometric pressure. Bubble growth thresholds were examined for a range of the above dependent parameters. / Science, Faculty of / Zoology, Department of / Graduate

Fish exposed to gas supersaturated water often experience a form of stress known as Gas Bubble Trauma (GBT). GBT is an acute condition involving various forms of bubble growth both internal and external to the animal. Theoretical models are developed which establish thresholds for bubble growth. These models apply to: 1. ) Bubble growth in the vascular systems of fish. 2. ) Bubble growth in the environmental water that can occur in the buccal cavity and between gill lamella. 4.) Overinflation of the swimbladder. 3. ) Sub-dermal bubbles that occur on external skin surfaces such as the opercular flaps, between fin rays and in the lining of the mouth. In order to develop the models for general use, it was necessary to establish the effective size of nucleation sites and other physiological parameters contained in the bubble growth threshold equations. This was accomplished through a review of data from the scientific literature and a two phase experimental program. The literature review resulted in the compilation of a database containing over 1000 records of supersaturation data on salmonids. Various filters based on length, species, total gas pressure (TGP), partial pressure of oxygen (PO₂) and other criteria were applied to the database. The filtering operations established the existence of GBT mortality thresholds and identified relationships between other experimental parameters. The results of this analysis suggest that a lower threshold occurs at a water TGP of 1.10 Atms. and a higher threshold occurs at 1.15 to 1.18 Atms. However, it was not established that the apparent mortality thresholds correspond to thresholds for bubble growth predicted by the theoretical models. To make this correlation, a preliminary experimental study examined the physiological response of fish exposed to supersaturated water. It was found that arterial PO₂, hematocrit and blood pressure yield unique responses to bubble growth over specific ranges of water TGP. The results of these experiments also indicate that the lower mortality threshold of the database analyses is associated with a combination of sub-dermal bubble growth in the mouth and extracorporeal bubbles growing between gill lamella. The second phase of experimental study included surveys of blood PO₂, hematocrit and pH along with microscopic studies of intravascular and extracorporeal bubble growth in gills. The results of these experiments confirm the source of mortality for the lower threshold at a water TGP of 1.1 Atms. In addition, the data demonstrate that the upper TGP threshold of 1.15 to 1.18 Atms. of the database analysis corresponds to the threshold for intravascular bubble growth. The results further confirm that, as predicted by the theoretical model, intravascular bubble growth thresholds are dependent on water PO₂ . Combining the results of the database analysis and the experimental studies permitted the effective size of nucleation sites responsible for bubble growth to be back calculated from the theoretical equations. This completed the development of the bubble growth threshold equations. The equations can now be used to predict thresholds for the various forms of bubble growth and mortality that occur in fish exposed to supersaturated water. The experimental results also provide valuable information regarding the physiological response of fish to gas supersaturated water. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Gas bubbles that form within water treatment plants can disrupt drinking water treatment processes. Bubbles may form whenever the total dissolved gas pressure exceeds the local solution pressure, a condition termed dissolved gas "supersaturation." This project investigated how bubble formation affects conventional drinking water treatment and examined factors that can reduce these problems. Gas bubbles attached to coagulated floc particles can reduce settling efficiency and create "floating floc." In laboratory experiments, bubbles formed on the surface of the mixing paddle, since this was the location of minimum pressure within the system. The formation and stability of floating floc was dependent on many different factors including the amount and type of dissolved gas supersaturation and surface chemistry of the mixing paddle. The intensity and duration of rapid mixing also controlled the amount of floating floc. Bubbles forming in filter media can block pore spaces and create headloss, a process popularly termed "air binding." During benchscale filtration experiments, bubbles were released upwards from the media in a burping phenomenon, and bubbles could also be pushed downwards by fluid flow. Burping is beneficial since it partly alleviates the bubble induced headloss, but the media disruptions might also decrease filter efficiency (particle capture). Bubble formation within filters can be reduced by increasing the pressure inside the filter via greater submergence (water head above the media), lower hydraulic flow rate, or use of a more porous media. The mode of filter operation (declining or constant flow rate) will also affect the local filter pressure profile. Dissolved gas supersaturation and bubble formation are detected in on-line turbidity devices and particle counters causing spurious measurements. The use of bubble traps usually reduced these problems, but one device worsened turbidity spikes. Flow disturbances may also release bubbles upstream of the on-line turbidimeter, which can cause spikes in turbidity readings. / Ph. D.

The gas assisted injection moulding process is an important extension to conventional injection moulding. Gas assist can be applied in a number of ways, but here the penetration of a gas bubble through the polymer melt is of interest. A 3D fi nite element implementation of a pseudo concentration method is employed to simulate the primary penetration of the gas bubble. The wall thickness prediction is an important result since the extent of bubble penetration is sensitive to the remaining melt fraction. A number of methods for experimental measurement are developed to measure characteristics of the gas assisted injection moulding process dynamics and product. Key process variables, on an industrial gas-assist machine, were measured and analysed, leading to an empirical model for wall thickness prediction. Gas delay time and injection velocity are shown to be most influential in controlling residual wall thickness. Simulation results are evaluated against the empirical model. The trends observed, for simulation and experiment, in wall thickness after changes in process variable settings are found to agree qualitatively. The wall thickness prediction is found to be within 10% of the experimentally obtained measurements.

Uranium-zirconium alloy nuclear fuels have many advantages as compared with ceramic fuels, especially for fast reactor systems. However, metallic fuels aren’t currently used in commercial power production due in part to issues with fuel swelling during irradiation. A major contributor to this expansion issue, the formation of fission gasses into bubbles, is examined here. Methods to evaluate evolution of fission gas bubbles within a U-Zr alloy are discussed and refined. Specifically, transmission electron microscopy (TEM) for viewing bubbles within the interior of the alloy is investigated. One constraint on the use of the TEM is the lack of literature pertaining to what thinning techniques are successful for U-10Zr alloy. Both initial and final thinning techniques were investigated. After thinning was complete, the specimens were viewed via TEM to determine their suitability. In addition, samples of U-Zr alloy were irradiated with gas atoms in an accelerator to simulate bubble initiation and formation and viewed via TEM. Only preliminary investigations were completed. Evaluated electrolyte solutions included one part phosphoric acid to two parts sulfuric acid and two parts water (A), one part phosphoric acid to one part ethanol and one part glycerol (B), one part hydrochloric acid to one part water (C), two parts methanol to 13 parts phosphoric acid (D), and one part perchloric acid to nine parts acetic acid (G). Positive responses were received from the solutions A, C, and G which generated electron transparent areas with few to no process induced artifacts. TEM trials with each electrolyte were performed on un-irradiated U-10Zr alloy. These trials indicated that the polishing methods would work but are not yet optimal. In addition, U-10Zr alloy was irradiated and viewed in the TEM where those polished with electrolyte A consistently included the presence of large circular features that could indicate bubbles or voids. The foundation was laid for further study to be done on this topic through the use of electropolishing solutions as final thinning techniques. Additional work that is recommended includes: electropolishing parameter refinement; implantation of heavier gas atoms or at elevated temperatures; annealing of the implanted alloy; and computer modeling of resulting first principles phenomena.

Thesis (M.S.)--Oregon State University, 2011. / Printout. Includes bibliographical references. Also available on the World Wide Web.

[pt] O escoamento de gás em fluidos complexos é um fenômeno presente em industrias como alimentos e bebidas, farmacêutica, química e petróleo e gás. Nesta pesquisa foi abordado o fenômeno de invasão de gás em pastas de cimento durante o processo de cimentação de poços de petróleo. Este problema é governado por diferentes parâmetros como tamanho, geometria e velocidade das bolhas, reologia do fluido, histórico de cisalhamento do material, pressão e vazão de injeção. Neste trabalho estuda-se experimentalmente a dinâmica de uma bolha de ar não esférica em regime de Stokes ou laminar, escoando em materiais que simulam pastas de cimento com diferentes níveis de viscosidade. As pastas de cimento e suas propriedades viscoplásticas e tixotrópicas são reproduzidas usando suspensões de Carbopol e Laponita, respectivamente. Apresenta-se também um modelo matemático simplificado para a dinâmica do fenômeno de migração de gás, com aplicação na indústria do petróleo. No estudo com Carbopo, investiga-se o efeito da tensão limite de escoamento e a relação entre forças viscosas e inerciais, e sua influência na dinâmica e na geometria da bolha de gás. A análise com Laponita visa simular o processo de invasão e migração de gás durante o processo de cura do cimento. O efeito da tixotropia no formato e na dinâmica de migração das bolhas é analisado. Estes resultados simulam também a complexa dinâmica da migração de gás em fluidos com reologia dependente do tempo, como as pastas de cimento ao longo de seu processo de cura. Observou-se a formação de bolhas de gás com geometria plana, que permitem o escoamento com baixa resistência e formam caminhos preferenciais, que podem se tornar canais de escoamento de gás a alta vazão. / [en] The gas flow in complex fluids is a phenomenon present in industries such as foods and beverage, pharmaceuticals, chemistry and oil and gas. In this research the phenomenon of gas invasion in cement pastes during the cementation process of wells of petroleum was analyzed. This problem is governed by different parameters such as bubble size, geometry and velocity, fluid rheology, material shear history, injection pressure and flow rate. In this work, we perform an experimental study of the dynamics of a non-spherical air bubble under a Stokes or laminar regime, flowing in materials that simulate cement pastes with different levels of viscosity. Cement pastes and their viscoplastic and thixotropic properties are reproduced using suspensions of Carbopol and Laponite, respectively. A simplified mathematical model for the dynamics of the phenomenon of gas migration, with application in the petroleum industry, is also presented. In the Carbopol study, the effect of the yield stress and the relationship between viscous and inertial forces and their influence on the dynamics and geometry of the gas bubble is investigated. The analysis with Laponite aims to simulate the process of invasion and gas migration during the cement cure process. The effect of thixotropy on the shape and dynamics of bubble migration is analyzed. These results also simulate the complex dynamics of gas migration in fluids with time dependent rheology, such as cement pastes during their curing process. The formation of gas bubbles with flat geometry has been observed, allowing the gas to flow with lower resistance and to form preferred paths that can become channels with high gas flow rates.

The gas assisted injection moulding process is an important extension to conventional injection moulding. Gas assist can be applied in a number of ways, but here the penetration of a gas bubble through the polymer melt is of interest. A 3D fi nite element implementation of a pseudo concentration method is employed to simulate the primary penetration of the gas bubble. The wall thickness prediction is an important result since the extent of bubble penetration is sensitive to the remaining melt fraction. A number of methods for experimental measurement are developed to measure characteristics of the gas assisted injection moulding process dynamics and product. Key process variables, on an industrial gas-assist machine, were measured and analysed, leading to an empirical model for wall thickness prediction. Gas delay time and injection velocity are shown to be most influential in controlling residual wall thickness. Simulation results are evaluated against the empirical model. The trends observed, for simulation and experiment, in wall thickness after changes in process variable settings are found to agree qualitatively. The wall thickness prediction is found to be within 10% of the experimentally obtained measurements. / EPSRC

[pt] Neste trabalho, um estudo do deslocamento ascendente de uma única bolha de gás num fluido não newtoniano é realizado ,a fim de simular o escoamento de bolhas de gás em pasta de cimento durante a cimentação de poços de petróleo. O fluido é modelado como um fluido não Newtoniano tipo Herschel-Bulkley com reologia variável no tempo. A partícula imersa no fluido não necessariamente é gasosa, também pode ser sólida ou liquida, fazendo algumas considerações para cada caso. Para desenvolver o modelo matemático foi feita uma analise dinâmica da partícula esférica imersa no fluido, e junto com as equações de Ansley e Plesley (1967), foi finalizado o modelo. O sistema de equações foi solucionado usando um método numerico de Runge Kutta de baixa ordem. O modelo numérico foi implementado usando o programa Matlab da empresa Mathworks. Os cálculos foram feitos para bolha esférica, numero de Reynolds baixo (menor 3), temperatura constante, efeito de parede desprezível e sem efeito de população. O modelo foi validado comparando os resultados numéricos com os resultados experimentais de multiples autores. Foram consultados os dados experimentais dos autores Raymond (2000), Hervé Tabuteau (2007) e Neville Dubash (2003). Foi analisado o efeito da massa da bolha e da tensão superficial da interface liquido-gás na cinemática da partícula, a fim de definir em que condições é possível desprezar seus efeitos. Finalmente, os efeitos dos parâmetros reológicos na cinemática da partícula são analisados. Além disso, considerou-se a dependência da reologia com o tempo a fim de analisar o processo de deslocamento da bolha durante a cura do cimento. / [en] In this work, a study of the rising movement of single gas bubble in non- Newtonian fluid is performed, in order to simulate the behavior of a gas bubble in a cement paste during oil well cementing. The fluid is modeled as a non- Newtonian fluid type Hershchel-bulkley with varying rheology in the time. The particle immersed in the fluid is not necessarily gaseous, it also could be liquid or solid, with some restrictions for each case. To develop the mathematical model, it was done a dynamic analysis of the spherical particle immersed in the fluid, and also, using the Ansley and Plesley’s equations (1967), was finished the model. The equation systems was solved using a low order numerical method of Runge Kutta. The numerical model was implemented using Matlab program of the Mathworks Company. The calculations were made for spherical bubble, low Reynolds number (less than 3), constant temperature, wall effect neglected and without effect population.The model was validated comparing the numerical data with experimental results of multiple authors. Experimental data was consulted of Raymond and Rosant (2000), Hervé Tabuteau (2007) and Neville Dubash (2003) authors. It was analyzed the bubble mass effect and the surface tension of the liquid-gas interface in the kinematic particle, to define under what conditions it is possible to neglected its effects. Finally,the effects of rheological parameters on particle kinematics was analized. furthermore, the dependence of the rheology in the time to determine the bubble displacement process in the curing cement was analized.