<p> Using a single bubble suspended in a liquid flow regime, the effects of velocity, bubble size, and surfactant levels on the gas transfer process across the bubble interface were investigated. Mass transfer data reported in the literature for non-circulating carbon dioxide bubbles was verified. A mathematical model predicting the mass transfer process for the single bubble system used in this study was formulated and this model provided a reasonable fit for experimental data obtained for the dissolution of a carbon dioxide bubble into an aqueous solution of a second sparingly soluble gas. The fate of a hypothetical air bubble in an aerator was briefly considered.</p> / Thesis / Master of Engineering (MEngr)

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This dissertation includes a theoretical and numerical development to simulate liquid-vapor flows and the applications to microchannels. First, we obtain a consistent non-local pressure equation for simulating liquid-vapor interfacial flows using mean-field free-energy theory. This new pressure equation is shown to be the general form of the classical van der Waals" square-gradient theory. The new equation is implemented in two-dimensional (2D) D2Q7, D2Q9, and three-dimensional (3D) D3Q19 lattice Boltzmann method (LBM). The three LBM models are validated successfully in a number of analytical solutions of liquid-vapor interfacial flows. Second, we have shown that the common bounceback condition in the literature leads to an unphysical velocity at the wall in the presence of surface forces. A few new consistent mass and energy conserving velocity-boundary conditions are developed for D2Q7, D2Q9, and D3Q19 LBM models, respectively. The three LBM models are shown to have the capabilities to successfully simulate different wall wettabilities, the three typical theories or laws for moving contact lines, and liquid-vapor channel flows. Third, proper scaling laws are derived to represent the physical system in the framework of the LBM. For the first time, to the best of the author's knowledge, we obtain a flow regime map for liquid-vapor channel flows with a numerical method. Our flow map is the first flow regime map so far for submicrochannel flows, and also the first iso-thermal flow regime map for CO₂ mini- and micro-channel flows. Our results show that three major flow regimes occur, including dispersed, bubble/plug, and liquid strip flow. The vapor and liquid dispersed flows happen at the two extremities of vapor quality. When vapor quality increases beyond a threshold, bubble/plug patterns appear. The bubble/plug regimes include symmetric and distorted, submerged and non-wetting, single and train bubbles/plugs, and some combination of them. When the Weber number<10, the bubble/plug flow regime turns to a liquid strip pattern at the increased vapor quality of 0.5~0.6. When the Weber number>10, the regime transition occurs around a vapor quality of 0.10~0.20. In fact, when an inertia is large enough to destroy the initial flow pattern, the transition boundary between the bubble and strip regimes depends only on vapor quality and exists between x=0.10 and 0.20. The liquid strip flow regimes include stratified strip, wavy-stratified strip, intermittent strip, liquid lump, and wispy-strip flow. We also find that the liquid-vapor interfaces become distorted at the Weber number of 500~1000, independent of vapor quality. The comparisons of our flow maps with two typical experiments show that the simulations capture the basic and important flow mechanisms for the flow regime transition from the bubble/plug regimes to the strip regimes and from the non-distorted interfaces to the distorted interfaces. Last, our available results show that the flow regimes of both 2D and 3D fall in the same three broad categories with similar subdivisions of the flow regimes, even though the 3D duct produces some specific 3D corner flow patterns. The comparison between 2D and 3D flows shows that the flow map obtained from 2D flows can be generally applied to a 3D situation, with caution, when 3D information is not available. In addition, our 3D study shows that different wettabilities generate different flow regimes. With the complete wetting wall, the flow pattern is the most stable. / Ph. D.

The oil and gas industry need for high performing and low cost multiphase meters is ever more justified given the rapid depletion of conventional oil reserves. This has led oil companies to develop smaller/marginal fields and reservoirs in remote locations and deep offshore, thereby placing great demands for compact and more cost effective soluti8ons of on-line continuous multiphase flow measurement. The pattern recognition approach for clamp-on multiphase measurement employed in this research study provides one means for meeting this need. Cont/d.

Plusieurs régimes d’écoulement diphasiques adiabatiques eau/air horizontaux (écoulements dispersés àbulles et intermittents) et leur développement axial ont été étudiés dans l'expérience METERO,constituée d’une conduite circulaire horizontale de 100 mm de diamètre interne. Différentes techniques d’instrumentation ont été améliorées et utilisées pour mesurer les grandeurs caractéristiques de l’écoulement afin d’apporter une description locale et l'évolution axiale des écoulements. Les mécanismes physiques responsables des régimes d’écoulement et de leurs transitions, notamment la compétition entre forces turbulente et de flottabilité ont été explicités. Les différences entre les régimes à bulles et intermittent ont été mises en évidence et les processus physiques à l’origine de ces différences ont été expliqués. Deux nouvelles cartes de régime d’écoulement adimensionnelles ont été proposées: la première apporte une amélioration à la représentation de Taitel & Dukler (1976) et propose un nouveau critère de transition. La deuxième, novatrice, quantifie les effets des forces de turbulence et de flottabilité en fonction du taux de vide. / Several horizontal water-air two-phase adiabatic flows (dispersed bubbly flows and intermittent flows)and their axial evolutions have been studied in the METERO experiment which is consisted of ahorizontal circular test section with an internal diameter of 100 mm. Different measurement techniqueshave been improved and utilized to measure the flow characteristics in order to bring a localdescription and axial evolution of the flows. The responsible physical mechanisms of the flow regimesand their transitions, particularly the competition between turbulent force and buoyancy force havebeen explained. The differences between dispersed bubbly flows and intermittent flows have beenhighlighted and the physical process at the origin of these differences has been explained. Two newdimensionless flow regime maps have been proposed: the first one brings an improvement to therepresentation of Taitel & Dukler (1976) and proposes new transition criteria. The second novel maptakes into account the effects of turbulent and buoyancy forces and the void fraction.

O transporte pneumático de sólidos constitui uma aplicação comum em processos industriais petroquímicos, de mineração, de alimentos e agrícola. Entretanto, devido a limitações de ordem prática, a maioria das aplicações existente envolve o transporte de 1 a 400 toneladas por hora, através de distâncias de até 1000 m. Entre estas limitações, o consumo de potência provavelmente é a mais severa. Um sistema de transporte seguro e que apresente uma redução no consumo de potência pode ser implementado com técnicas não convencionais de controle. Este trabalho descreve a implementação de um controlador difuso em um circuito experimental de 45 mm de diâmetro interno utilizado para transportar sementes de Setaria Itálica ao longo de 21 metros. Informações obtidas com um estudo prévio de identificação de regimes gás - sólido através de redes neurais auto-organizáveis foram utilizadas no projeto do controlador. Os resultados mostraram uma redução significativa de 41%, em média, no consumo de potência requerida para o transporte de uma mesma carga de sólido. / The pneumatic conveying of solids in a gas stream is a recurrent process in petrochemical industries as well as in agricultural, food and mining. However, due to practical limitations the majority of existing systems have capacities ranging from 1 to 400 tones per hour over distances less than 1000 m, mainly because of a high power consumption per transported unit mass. A safe circuit with reduced power consumption can be designed using non-conventional control techniques. This work describes a fuzzy controller implementation for a 45 mm i.d. pneumatic conveying system used to transport Setaria Italica seeds over a distance of 21 m. Data obtained in a previous study about gas-solid flow regime identification through a self-organizing neural network were used in the controller design. The results show that reduction in power consumption can reach 41% when compared with classical non controller transport.

The oil and gas industry need for high performing and low cost multiphase meters is ever more justified given the rapid depletion of conventional oil reserves. This has led oil companies to develop smaller/marginal fields and reservoirs in remote locations and deep offshore, thereby placing great demands for compact and more cost effective soluti8ons of on-line continuous multiphase flow measurement. The pattern recognition approach for clamp-on multiphase measurement employed in this research study provides one means for meeting this need. Cont/d.

This project focused on the relationship between instream flows and smallmouth buffalo (Ictiobus bubalus) recruitment in the Gulf Coastal Plain of Texas. The flow regime is the dominant factor in lotic systems and, consequently, the relationship between instream flows, including impacts to natural flow regimes, and life-history is a subject of growing interest. Smallmouth buffalo is a good model to investigate the relationship between river flows and variable interannual recruitment success of periodic life-history strategist fish species. Smallmouth buffalo were collected from the Brazos, Colorado, and Guadalupe Rivers of Texas, U.S.A., and otoliths were extracted from individuals in the field and sectioned and photographed in the lab. Photographs of sectioned otoliths were used to estimate age and thus the year in which the individual was spawned by counting back from the time of capture. Population age structure (i.e. a ‘state' or condition at a point in time) was used to infer effects of flow variation on a rates-based process (i.e. recruitment). After controlling for mortality using recruitment index values, interannual variation in recruitment was modeled using multiple components of the flow regime quantified as indicators of hydrologic alteration (IHA) variables based on daily discharge data from USGS gaging stations in each river system. Model selection followed a two-tier approach, first fitting models using only flow attributes associated with the spawning season then adding additional informative parameters from the pre-spawn and post-spawn periods. The primary finding from model selection was that duration of high flow pulses during the spawning season is a critical component of the flow regime associated with successful Smallmouth Buffalo recruitment. These findings have implications for river management and conservation of ecological integrity, in particular populations of periodic life-history strategist species.

O transporte pneumático de sólidos constitui uma aplicação comum em processos industriais petroquímicos, de mineração, de alimentos e agrícola. Entretanto, devido a limitações de ordem prática, a maioria das aplicações existente envolve o transporte de 1 a 400 toneladas por hora, através de distâncias de até 1000 m. Entre estas limitações, o consumo de potência provavelmente é a mais severa. Um sistema de transporte seguro e que apresente uma redução no consumo de potência pode ser implementado com técnicas não convencionais de controle. Este trabalho descreve a implementação de um controlador difuso em um circuito experimental de 45 mm de diâmetro interno utilizado para transportar sementes de Setaria Itálica ao longo de 21 metros. Informações obtidas com um estudo prévio de identificação de regimes gás - sólido através de redes neurais auto-organizáveis foram utilizadas no projeto do controlador. Os resultados mostraram uma redução significativa de 41%, em média, no consumo de potência requerida para o transporte de uma mesma carga de sólido. / The pneumatic conveying of solids in a gas stream is a recurrent process in petrochemical industries as well as in agricultural, food and mining. However, due to practical limitations the majority of existing systems have capacities ranging from 1 to 400 tones per hour over distances less than 1000 m, mainly because of a high power consumption per transported unit mass. A safe circuit with reduced power consumption can be designed using non-conventional control techniques. This work describes a fuzzy controller implementation for a 45 mm i.d. pneumatic conveying system used to transport Setaria Italica seeds over a distance of 21 m. Data obtained in a previous study about gas-solid flow regime identification through a self-organizing neural network were used in the controller design. The results show that reduction in power consumption can reach 41% when compared with classical non controller transport.