<p>The laminar natural convection in air-filled rectangular cavities with and without a partition on the wall was experimentally investigated. Temperature measurements and flow visualizations were performed for cases with heated and cooled vertical walls (corresponding to global Grashof numbers GrH of approximately 1.4 x 10^8 to 1.8 x 10^8) and non-dimensional top wall temperatures θT of 0.52 (insulated) to 2.3. In the rectangular cavities without the partition and with aspect ratios of 0.5, 1.0 and 2.0, the heated top wall caused the natural convection boundary layer flow to separate from either the top wall (for the cases with Or ;S 1.2) or the heated vertical wall (for the cases with θT >~ 1.2) due to the negative buoyancy force. For the cases with θT >~ 1.2, there is an anti-clockwise recirculating flow in the upper left corner region. The extent of the recirculating flow decreased with an increase of the aspect ratio. The temperature gradient in the core region, dθ∞ /d(y/H), increased with an increase of θT. For a given aspect ratio, dθ∞/d(y/H) changed more rapidly with the change in θT for the cases with θT <~ 1.2 compared to the cases with θT >~ 1.2. The increase in dθ∞/ d(y/H) was more significant for the smaller aspect ratio cavity. The temperature profiles predicted from the similarity solutions proposed by Kulkarni et al. [1] and from the non-similarity model developed by Chen and Eichhorn [2] for natural convection on an isothermal vertical wall in a stratified environment were compared to the measurements in the current cases. These models were not able to accurately describe the characteristics of the natural convection flow in the rectangular cavities.</p> <p>An aluminium partition with non-dimensional heights Hp/H of 0.0625 and 0.125 was attached either to the heated vertical wall or top wall at y/H = 0.65, 0.95 and x/H = 0.1, 0.2, 0.4 and 0.6 to study the effect of the partition on the laminar natural convection flow in a square cavity. The blockage and thermal effects of the partition resulted in changes in the temperature and flow fields, but were mainly limited in the vicinity of the partition. The effect of the partition changed with the height and location of the partition. When the partition was attached to the heated top wall, a recirculating flow was formed between the partition and the heated vertical wall. For a given partition height, the structure of this recirculating flow was dependent on the partition location and θT. A thermal boundary layer developed along the rear surface of the partition due to the thermal effect of the partition. The ambient temperature outside the boundary layer and Nu near the corner region were affected by the partition height due to the changes in the recirculating flow and the rear surface of the partition.</p> / Thesis / Doctor of Philosophy (PhD)

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No description available.

Master of Science

A three-dimensional linear stability analysis is presented for two-dimensional boundary layer flows. The method of multiple scales is used to derive the amplitude and the wave number modulation equations, which take into account the nonparallelism of the basic flow. The zeroth-order eigenvalue problem is numerically integrated to calculate the quasi-parallel growth rates which are then integrated together with the nonparallel growth rates along the characteristics of the wave number modulation equations to evaluate the n-factors. The n-factors are used to determine the most dangerous frequency. The most critical frequency is defined to be the one that yields the n-factor corresponding to transition in the shortest possible distance. This definition is used to evaluate the critical frequency for the Blasius boundary layer, a wedge flow and an axisymmetric boundary layer. The effect of three-dimensional disturbances is evaluated and found to be less critical than two-dimensional disturbances regardless of the pressure gradient, the temperature distribution of the wall and the wall geometry. The effect of heating the boundary layer is evaluated for the Blasius, Falkner-Skan and axisymmetric boundary layers. In all the cases considered, heating substantially reduces the n-factors. Results are compared with those of Strazisar & Reshotko (1978) and Nayfeh & El-Hady (1980). / Ph. D.

Este trabalho apresenta os resultados da avaliação da erosão pluvial laminar utilizando modelos físico-matemáticos, baseados na Equação Universal de Perda de Solo (EUPS), na bacia hidrográfica da Represa do Lobo (Broa), municípios de Itirapina e Brotas, SP, em ambiente de Sistema de Informação Geográfica (SIG) utilizando ferramentas do SIG ArcGis. Neste estudo, busca-se também aplicar a EUPS considerando dois métodos distintos de cálculo do fator topográfico (LS). Com o escopo de atingir tais objetivos, compilaram-se dados da pedologia, geologia, dados pluviométricos, cálculo do fator LS e usos, manejo e práticas conservacionistas obtidas do mosaico de imagem de satélite do aplicativo Google Earth. Os respectivos mapas temáticos e dos fatores da EUPS foram elaborados na escala de trabalho 1:50.000, que permitiu gerar o Mapa de Perda de Solo e seus índices do risco de erosão derivados, tais como: Potencial Natural de Erosão, Risco de Erosão Natural, Risco de Erosão Simulado e a Expectativa de Erosão, da bacia hidrográfica da Represa do Lobo. Duas metodologias distintas foram aplicadas para o cálculo do fator LS de forma automatizada: o primeiro método baseou-se na equação proposta por Moore e Wilson (1992); e a segunda corresponde à equação de Desmet e Goovers (1996) para determinar o Fator L e a equação sugerida por Nearing (1997) para o Fator S. O diagnóstico da perda de solo por unidade de área por tempo permitiu identificar as áreas mais suscetíveis aos processos erosivos. Os resultados demonstram que a bacia hidrográfica da Represa do Lobo apresenta suscetibilidade predominantemente baixa em 90,36% e 42,82% da área, respectivamente para os métodos 1 e 2, com perda de solo tolerável e expectativa de erosão predominantemente ausente, ou seja, o uso e manejo do solo atual estão provocando erosão abaixo do limite de tolerância. As taxas de perda de solo por erosão variaram de 0 a > 200 t.ha-1.ano-1 conforme o método de cálculo do fator LS. A incidência de feições erosivas e erosões lineares estão relacionadas com as áreas identificadas com maior suscetibilidade aos processos erosivos. / This work presents the results of an evaluation of the laminar rain erosion, using physical and mathematical models based on the Universal Soil Loss Equation (USLE) in Geographic Information System (GIS) using tools of the software ArcGIS. The case study was performed in the Lobo Reservoir Watershed, also known as Broa, situated in the Itirapina and Brotas cities, São Paulo state (Brazil). This study also seeks to considerer two different methods of the topographic factor calculation (LS) in the USLE application. In order to achieve these objectives, was compiled pedology, geology and rainfall data, the calculation of the LS factor and use, management and conservation practices obtained from the satellite images mosaic of the Google Earth application. The thematic maps and the maps from the USLE factors were developed in the work scale 1:50.000, allowing generating the Soil Loss Map and its derivatives erosion risks indexes, such as: Erosion Natural Potential, Natural Erosion Risk, Simulated Erosion Risk and the Erosion Expectation in the Lobo Reservoir Watershed. Two different methodologies were applied to calculate the LS factor: the first of them was based on the equation proposed by Moore and Wilson (1992); and the second one corresponds to Desmet and Goovers (1996) and Nearing (1997), to determine the L and S factors, respectively. The diagnosis of the soil loss per unit area per time allowed identifying the most susceptible areas to erosion processes. The results shows that the Lobo Reservoir Watershed has a very low soil loss susceptibility at 90,36% and 42,82% of the area, for the methods 1 and 2, respectively, revealing tolerable soil loss and absence of erosion expectation, for most of the area. In this case, the use and management of the soil causes erosion below of the tolerance limit. The soil loss rates by erosion ranged from 0 to > 200 t.ha-1.year-1, according to the LS factor calculation method. The incidence of erosive features and linear erosions are associated to the areas identified with higher susceptibility to erosion processes.

Os trocadores de calor tubulares são muito utilizados para o processamento térmico de alimentos líquidos viscosos por possuírem um maior diâmetro hidráulico em comparação aos trocadores de calor a placas. O cálculo da letalidade neste tipo de trocador está diretamente relacionado ao perfil de velocidade e à distribuição do tempo de residência (DTR). Para escoamento laminar de fluidos viscosos, Newtonianos e não-Newtonianos, geralmente adota-se um perfil de velocidade laminar e de lei de potência, respectivamente. No entanto, algumas características do equipamento como irregularidades na tubulação, a corrugação do tubo ou as curvas podem modificar o perfil de velocidade ideal. Esse desvio da idealidade pode ser caracterizado através da determinação experimental da distribuição do tempo de residência do processo. Este trabalho teve como objetivo a determinação experimental da DTR de fluidos viscosos em um equipamento bitubular de processamento térmico e o ajuste do perfil de velocidade associado. Modelos clássicos de DTR foram ajustados aos dados, assim como foram propostos e testados novos modelos generalizados de DTR, a fim de caracterizar o escoamento laminar não ideal em tubos. A determinação da DTR experimental foi realizada para vazões entre 10 e 50 L/h utilizando água, solução de carboximeticelulose 1,0% (pseudoplástico) e mistura glicerina/água 80%. Os dados de DTR foram obtidos através de duas técnicas: condutimétrica e colorimétrica. A primeira técnica baseia-se na injeção de solução saturada de cloreto de sódio e detecção online por um condutivímetro, porém, não apresentou resultados satisfatórios mostrando que o método não é adequado para fluidos viscosos. Já a segunda técnica utilizada se baseia na injeção de corante e posterior detecção em espectrofotômetro. Os modelos que melhor se ajustaram aos dados experimentais para os três fluidos estudados foram os modelos generalizados y-laminar e exponencial. A letalidade foi calculada a partir da distribuição de temperatura no trocador de calor em estado estacionário e do tempo médio de residência obtido experimentalmente e permitiu detectar o sobreprocessamento no processo estudado. / Tubular heat exchangers are widely used for thermal processing of viscous liquid foods because they have larger hydraulic diameters than the plate heat exchangers. The calculation of lethality in this type of exchanger is directly related to velocity profile and the residence time distribution (RTD). For the laminar flow of viscous fluids, Newtonian and non-Newtonian, generally laminar and power law velocity profiles are used, respectively. However, some features of the equipment as irregularities in the pipe, the corrugation of the pipe or the presence of curves can change the ideal velocity profile. This ideality deviation can be characterized through the experimental determination of the residence time distribution of the process. The aim of this work was the experimental determination of the RTD of a viscous fluid in a bitubular thermal processing equipment and the determination of the associated velocity profile. Classic models of RTD were fitted to the data, as well as were proposed and tested new generalized models of RTD, in order to characterize the non ideal laminar flow in tubes. The experimental determination of RTD was performed to volumetric flow rates between 10 and 50 L/h using water, carboximeticelulose solution 1,0% (pseudoplastic) and glycerin/water mixture 80%. The RTD data were obtained through two techniques: conductimetric and colorimetric. The first technique is based on injection of saturated solution of sodium chloride and online detection with a conductivimeter however, unsatisfactory results showed that the method was not suitable for viscous fluids. The second technique is based on the injection of dye and subsequent detection with a spectrophotometer. The best fitted models to the experimental data for the three studied fluids were: ylaminar and exponential generalized models. The lethality was calculated from the temperature distribution in the heat exchanger at steady state and average residence time obtained experimentally and allowed the evaluation of the overprocessing of this process.

Este trabalho apresenta os resultados da avaliação da erosão pluvial laminar utilizando modelos físico-matemáticos, baseados na Equação Universal de Perda de Solo (EUPS), na bacia hidrográfica da Represa do Lobo (Broa), municípios de Itirapina e Brotas, SP, em ambiente de Sistema de Informação Geográfica (SIG) utilizando ferramentas do SIG ArcGis. Neste estudo, busca-se também aplicar a EUPS considerando dois métodos distintos de cálculo do fator topográfico (LS). Com o escopo de atingir tais objetivos, compilaram-se dados da pedologia, geologia, dados pluviométricos, cálculo do fator LS e usos, manejo e práticas conservacionistas obtidas do mosaico de imagem de satélite do aplicativo Google Earth. Os respectivos mapas temáticos e dos fatores da EUPS foram elaborados na escala de trabalho 1:50.000, que permitiu gerar o Mapa de Perda de Solo e seus índices do risco de erosão derivados, tais como: Potencial Natural de Erosão, Risco de Erosão Natural, Risco de Erosão Simulado e a Expectativa de Erosão, da bacia hidrográfica da Represa do Lobo. Duas metodologias distintas foram aplicadas para o cálculo do fator LS de forma automatizada: o primeiro método baseou-se na equação proposta por Moore e Wilson (1992); e a segunda corresponde à equação de Desmet e Goovers (1996) para determinar o Fator L e a equação sugerida por Nearing (1997) para o Fator S. O diagnóstico da perda de solo por unidade de área por tempo permitiu identificar as áreas mais suscetíveis aos processos erosivos. Os resultados demonstram que a bacia hidrográfica da Represa do Lobo apresenta suscetibilidade predominantemente baixa em 90,36% e 42,82% da área, respectivamente para os métodos 1 e 2, com perda de solo tolerável e expectativa de erosão predominantemente ausente, ou seja, o uso e manejo do solo atual estão provocando erosão abaixo do limite de tolerância. As taxas de perda de solo por erosão variaram de 0 a > 200 t.ha-1.ano-1 conforme o método de cálculo do fator LS. A incidência de feições erosivas e erosões lineares estão relacionadas com as áreas identificadas com maior suscetibilidade aos processos erosivos. / This work presents the results of an evaluation of the laminar rain erosion, using physical and mathematical models based on the Universal Soil Loss Equation (USLE) in Geographic Information System (GIS) using tools of the software ArcGIS. The case study was performed in the Lobo Reservoir Watershed, also known as Broa, situated in the Itirapina and Brotas cities, São Paulo state (Brazil). This study also seeks to considerer two different methods of the topographic factor calculation (LS) in the USLE application. In order to achieve these objectives, was compiled pedology, geology and rainfall data, the calculation of the LS factor and use, management and conservation practices obtained from the satellite images mosaic of the Google Earth application. The thematic maps and the maps from the USLE factors were developed in the work scale 1:50.000, allowing generating the Soil Loss Map and its derivatives erosion risks indexes, such as: Erosion Natural Potential, Natural Erosion Risk, Simulated Erosion Risk and the Erosion Expectation in the Lobo Reservoir Watershed. Two different methodologies were applied to calculate the LS factor: the first of them was based on the equation proposed by Moore and Wilson (1992); and the second one corresponds to Desmet and Goovers (1996) and Nearing (1997), to determine the L and S factors, respectively. The diagnosis of the soil loss per unit area per time allowed identifying the most susceptible areas to erosion processes. The results shows that the Lobo Reservoir Watershed has a very low soil loss susceptibility at 90,36% and 42,82% of the area, for the methods 1 and 2, respectively, revealing tolerable soil loss and absence of erosion expectation, for most of the area. In this case, the use and management of the soil causes erosion below of the tolerance limit. The soil loss rates by erosion ranged from 0 to > 200 t.ha-1.year-1, according to the LS factor calculation method. The incidence of erosive features and linear erosions are associated to the areas identified with higher susceptibility to erosion processes.

A series of flight tests was performed using a swept-wing model mounted on a Cessna O-2 aircraft. The crossflow waves on the airfoil were excited by pneumatic spanwise-periodic distributed roughness elements (DREs). The objective of the experiment was to determine the roughness receptivity i.e. the relationship between roughness height and the amplitude of the unstable crossflow wave. The local skin-friction variation was measured using an array of calibrated and temperature-compensated hotfilm sensors. The amplitudes of the disturbance shear stress were compared to the amplitudes of the DREs. It was found that there is a relationship between the shear stress and DRE amplitude that needs to be studied more before any definitely conclusions can be made. It was also found that the sensitivity of the crossflow to DREs is highly dependent on the freestream turbulence levels.

Interactions of cells with their chemical microenvironments are critical to many polarized processes, including differentiation, migration, and pathfinding. To investigate such cellular events, tools are required that can rapidly reshape the microscopic chemical landscapes presented to cultured cells. Existing chemical dosing technologies rely on use of pre-fabricated chemical gradients, thus offering static cell-reagent interactions. Such interactions are particularly limiting for studying migration and chemotaxis, during which cells undergo rapid changes in position, morphology, and intracellular signaling. This dissertation describes the use of laminar streams, containing cellular effector molecules, for precise delivery of effectors to selected subcellular regions. In this approach, cells are grown on an ultra-thin polymer membrane that serves as a barrier to an underlying reagent reservoir. By using a tightly-focused pulsed laser beam, micron-diameter pores can be ablated in the membrane upstream of desired subcellular dosing sites. Emerging through these pores are well-defined reagent streams, which dose the targeted regions. Multiple pores can be ablated to allow parallel delivery of effector molecules to an arbitrary number of targets. Importantly, both the directionality and the composition of the reagent streams can be changed on-the-fly under a second to present dynamically changing chemical signals to cells undergoing migration. These methods are applied to study the chemotactic responses of neutrophil precursor cells. The subcellular localization of the chemical signals emerging through pores is found to influence the morphological evolution of these motile cells as they polarize and migrate in response to rapidly altered effector gradients. / text