Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2013 / The flow of reactive viscous fluids in porous media presents a theoretically challenging problem and has a broad range of scientific, technological and engineering applications. Real life areas where such flow systems are encountered include drying of food, geothermal energy extraction, nuclear waste disposal, the flow of heat and fluid inside human organs, insulation of buildings, groundwater movement, oil and gas production, astrophysical plasmas, magnetohydrodynamic (MHD) pumps and generators, metal extraction and granulation of metals, aerospace and ship propulsion and automobile exhaust systems. The reactions within such flow systems are inherently exothermic. It is in this view that we carry out studies of thermal effects and thermal stability criteria for unsteady flows of reactive variable viscosity non-Newtonian fluids through saturated porous media. The study focuses on non-Newtonian fluids mainly because the majority of industrial fluids exhibit non-Newtonian character. Particular focus will be on fluids of the differential type exemplified by third grade fluid. Both analytical and numerical techniques were employed to solve the nonlinear partial differential equations that were derived from the conservation principles, namely the principles of conservation of mass, momentum and energy balance. Graphical representations were adopted in trying to explain the response of solutions to various flow parameter variations. In chapter 1 we defined important terms and expressions, laid down a summary of important applications, carried out literature survey, stated the statement of the problem, the aims and objectives of the study as well as an outline of the envisaged research methodology. Chapter 2 focuses on the derivations of the fundamental equations that derive the flow system. These are the continuity equation, the momentum equation and the energy equation. In chapter 3 we computationally investigated the unsteady flow of a reactive temperature dependent viscosity third grade fluid through a porous saturated medium with asymmetric convective boundary conditions. The response of velocity and temperature fields to each of the various flow parameters was analysed and interpreted. A transient increase in both the velocity and temperature profiles with an increase in the reaction strength, viscous heating and fluid viscosity parameter was observed. On the other hand, a transient decrease in the field properties was observed with increase in non-Newtonian character and the porous medium shape parameter. The reaction was noticed to blow-up if, depending on other flow parameters, the reaction strength is not carefully controlled.

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.

Orientadores: Vivaldo Silveira Junior, Javier Telis Romero / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-06T15:00:42Z (GMT). No. of bitstreams: 1 Gratao_AnaCarolinaAmaral_D.pdf: 2034155 bytes, checksum: 7a7cc4a961cab6b38ae3dc5ee5f3f9d8 (MD5) Previous issue date: 2006 / Doutorado / Engenharia de Alimentos / Doutor em Engenharia de Alimentos

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The work presented in this thesis was performed with the aim of developing improved prediction methods for aerodynamic and aeroelastic analysis to be used in aircraft design. The first part of the thesis concerns the development of a viscous-inviscid interaction model for steady aerodynamic predictions. Since an inviscid, potential flow, model already is available, the main focus is on the development of a viscous model consisting of a three-dimensional integral boundary layer model. The performance of the viscous-inviscid interaction model is evaluated and it is found that the accuracy of the predictions as well as the computational cost appear to be acceptable for the intended application. The presented work also includes an experimental study aimed at analyzing steady and unsteady aerodynamic characteristics of a laminar flow wing model. An enhanced understanding of these characteristics is presumed to be useful for the development of improved aerodynamic prediction models. A combination of nearly linear as well as clearly nonlinear aerodynamic variations are observed in the steady as well as in the unsteady experimental results and it is discussed how these may relate to boundary layer properties as well as to aeroelastic stability characteristics. Aeroelastic considerations are receiving additional attention in the thesis, as a method for prediction of how flutter characteristics are affected by modeling uncertainties is part of the presented material. The analysis method provides an efficient alternative for obtaining increased information about, as well as enhanced understanding of, aeroelastic stability characteristics. / <p>QC 20170816</p>

[pt] Objetivo: Uma parte significativa das reservas mundiais de petróleo é encontrada na forma de óleos pesados. Estes óleos pesados possuem alta viscosidade de 100 - 10000 cP, que torna seu transporte altamente complexo e custoso. Vários métodos foram desenvolvidos para reduzir a perda de carga de escoamentos laminares de óleos de alta viscosidade. Entre os mais utilizados, pode-se citar o bombeio de um fluido de baixa viscosidade perto da parede do tubo com o óleo viscoso sendo transportado no centro, conhecido como core-annular flow. Neste trabalho, uma alternativa ao core-annular flow é estudada. O método é baseado na utilização de micro ranhuras da parede do duto preenchidas com um liquido de baixa viscosidade. Este método tem o potencial de evitar alguns dos problemas que ocorrem no uso de core-annular flow. A análise do efeito das diferentes propriedades dos fluidos, condições de operação, geometria das ranhuras na perda de carga do escoamento foi feita através de um estudo numérico e experimental. Resultados indicam as limitações e potencialidade do uso de micro ranhuras na reduçãode perda de carga de escoamento laminar. / [en] Objective: A significant portion of the world oil reserves is found in the form of heavy oil. These oils have a high values of viscosity around 100-10000 cP, that makes their transportation complex and expensive. Several methods have been developed to reduce the pressure drop in laminar flows of high viscosity oils. Among them is the solution of pumping a liquid of lower viscosity near the pipe wall with the high viscosity oil flowing in the center. This method is known as Core-annular flow. In this work, an alternative to core-annular flow is studied. The method is based on the use of micro grooves in the pipe wall filled with a liquid of smaller viscosity. This method has the potential to elude some problems that occur with the core-annular flow method. The analysis of the drag reduction effect as a function of different fluids properties, operational conditions and geometry of the grooved walls was made using a numerical and experimental approach. Results indicate the limitations and potential of using micro grooves for drag reduction in laminar flows of high viscosity fluids.

The principal objective of this study is to investigate, develop and verify a framework for determining the convective heat transfer co-efficient from a cylindrical model that can easily be adaptable to more complex geometry - more specifically the human body geometry. Analysis of the model under forced convection airflow conditions between the transition velocity of about 1m/s - calculated using the Reynolds number - up until 12m/s were carried out. The boundary condition, however, also included differences in turbulence intensities and cylinder orientation with respect to wind flow (seen as wind direction in some texts). A total of 90 Computational Fluid Dynamic (CFD) calculations from these variations were analysed for the model under forced convective flow. Similar analysis were carried out for the model under natural convection with air flow velocity of 0.1m/s. Here, the temperature difference between the model and its surrounding environments and the cylinder orientation with respect to wind flow were varied to allow for a total of 15 CFD analysis. From these analysis, for forced convection, strong dependence of the convective heat transfer coefficient on air velocity, cylinder orientation and turbulence intensity was confirmed. For natural convection, a dependence on the cylinder orientation and temperature difference between the model and its environment was confirmed. The results from the CFD simulations were then compared with those found in texts from literature. Formulas for the convective heat transfer coefficient for both forced and natural convection considering the respective dependent variables are also proposed. The resulting formulas and the step by step CFD process described in this thesis provides a framework for the computation of the convective heat transfer coefficient of the human body via computer aided simulations. This framework can easily be adaptable to the convective heat transfer coefficient calculations of the human body with some geometric modelling adjustments, thus resulting in similar representative equations for a human geometric model.

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Design of Controlled Environment for Tissue Engineering Malcolm Lapera Tissue engineering aims at relieving the need for donor tissue and organs by developing a process of creating viable tissues in the laboratory setting. With over 120,000 people awaiting a transplant, the need for generating tissue engineered organs is very large [3]. In order for organs to be engineered, a few issues need to be overcome. A work space that both creates an environment which maintains cell viability over an extended period of time as well as accommodates the necessary fabrication equipment will be needed to further tissue engineering research. Therefore, a design for a “Tissue Engineering Hood,” will be developed and evaluated. The goal of this design will provide an environment capable of providing 37°C, 95% humidity, and 5% CO2, actively deter contamination, and provide the necessary support hardware for a 3D printer designed for tissue engineering. The design detailed in this paper was implemented successfully and evaluated. The current design has issues creating the proper environmental conditions, however does actively prevent contamination, and provides the necessary support hardware for a 3D printer. The current design was capable of reaching a temperature of 32°C, had issues increasing the humidity while incorporating the laminar air flow aspect of the design, and design flaws in the door allowed CO2 to leak too rapidly. After remedying these and a few other minor issues described in the report, the tissue engineering hood will be a beneficial tool for use in tissue engineering.

An experimental examination of crossflow instability and transition on a 45° swept wing is conducted in the Arizona State University Unsteady Wind Tunnel. The stationary-vortex pattern and transition location are visualized using both sublimating-chemical and liquid-crystal coatings. Extensive hot-wire measurements are conducted at several measurement stations across a single vortex track. The mean and travelling-wave disturbances are measured simultaneously. Stationary-crossflow disturbance profiles are determined by subtracting either a reference or a span-averaged velocity profile from the mean-velocity data. Mean, Stationary-crossflow, and travelling-wave velocity data are presented as local boundary-layer profiles and as contour plots across a single stationary-crossflow vortex track. Disturbance-mode profiles and growth rates are determined. The experimental data are compared to predictions from linear stability theory. Comparison of measured and predicted pressure distributions shows that a good approximation of infinite swept-wing flow is achieved. A fixed-wavelength vortex pattern is observed throughout the visualization range. The theoretically-predicted maximum-amplified vortex wavelength is found to be approximately 25% larger than the observed wavelength. Linear-stability computations for the dominant stationary-crossflow vortices show that the N-factors at transition ranged from 6.4 to 6.8. The mean-velocity profiles vary slightly across the stationary-crossflow vortex at the first measurement station. The variation across the vortex increases with downstream distance until nearly all of the profiles become highly-distorted S-shaped curves. Local stationary-crossflow disturbance profiles having either purely excess or deficit values develop at the upstream measurement stations. Further downstream the profiles take on crossover shapes not anticipated by the linear theory. The maximum streamwise stationary-crossflow velocity disturbances reach +20% of the edge velocity just before transition. The travelling-wave disturbances have single lobes at the upstream measurement stations as expected, but further downstream double-lobed travelling-wave profiles develop. The maximum disturbance intensity remains quite low until just ahead of the transition location where it suddenly peaks at 0.7% of the edge velocity and then drops sharply. The travelling-wave intensity is always more than an order of magnitude lower than the stationary crossflow-vortex strength. The mean streamwise-velocity contours are nearly flat and parallel to the model surface at the first measurement station. Further downstream, the contours rise up and begin to roll over like a wave breaking on the beach. The stationary-crossflow contours show that a plume of low-velocity fluid rises near the center of the wavelength while high-velocity regions develop near the surface at each end of the wavelength. There is no distinct pattern to the low-intensity travelling-wave contours until a short distance upstream of the transition location where the travelling-wave intensity suddenly peaks near the center of the vortex and then falls abruptly. The experimental disturbance-mode profiles agree quite well with the predicted eigenfunctions for the forward measurement stations. At the later stations, the experimental mode profiles assume double-lobed shapes with maxima above and below the single maximum predicted by the linear theory. The experimental growth rates are found to be less than or equal to the predicted growth rates from the linear theory. Also, the experimental growth rate curve oscillates over the measurement range whereas the theoretically-predicted growth rates decrease monotonically. / Ph. D.