The main objective of the research was to develop a means of numerically predicting the turbulent flow field in a baffled agitated vessel. This has been achieved by way of the 'k-e' model of turbulence. An extensive review of the literature on turbulence modelling is given to support that choice. A range of experimental studies concerning the flow in an agitated vessel, which is driven by a turbine having flat vertical blades, is reviewed for the purposes of validating predictions, and setting boundary conditions. Qualitative agreement only is found between the predictions and experimental data for the three mean velocity components at places where such data is available. The vertical plane flow pattern is in qualitative agreement with observations. This will remain the case until more detailed experimental measurements are made. Swirl velocity predictions are much less certain than the vertical plane components, however. This is attributed to the assumption that gradients in the circumferential direction can be neglected. To account directly for swirl reducing baffles, it is shown that a specially constructed source term in the swirl momentum equation, may lead to a realistic simulation of their effect. Comparisons of turbulence predictions are difficult to make in view of a general lack of reliable data. The results of this work are encouraging however, in that impeller stream turbulence is shown to be highly non-homogeneous, while turbulence in the recirculation zones is homogeneous by comparison, except near walls. Furthermore, turbulence variable distributions seem to be qualitatively correct though magnitudes are much less certain. The integrated rate at which turbulence kinetic energy is dissipated into heat, is predicted to be equally divided between the impeller stream and recirculation zones. Finally, it is shown that there is much scope for improving the model through a closer examination of impeller boundary conditions, by adapting more appropriate models to simulate baffle effects, and from wider comparison with experimental data by varying the system geometry.

Neste trabalho apresentamos um estudo da dinâmica de subsistemas quânticos dando ênfase ao fenômeno da decoerência. Em particular, estudamos os efeitos da decoerência num sistema de dois níveis acoplado a um outro sistema cujo espectro de energia é um contínuo no contexto do fenômeno quântico de tunelamento. Investigamos também aspectos da relação entre a descrição do sistema de dois níveis e a descrição do modelo linear na aproximação de onda girante em termos de uma equação mestra na aproximação de Born-Markov e a dinâmica exata destes dois subsistemas. Estudamos também o experimento proposto por L. Davidovich e colaboradores para medir a decoerência de superposições mesoscópicas de estados coerentes dentro do contexto da computação quântica. Este experimento pode ser re interpretado como um computador quântico capaz de solucionar o problema de Deutsch. O grande problema deste experimento, do ponto de vista da computação quântica, é a presença da decoerência. Esta decoerência provoca o aparecimento de erros no resultado final. Assim, nós mostramos uma maneira de reduzi-la, diminuindo assim os eventuais erros que possam aparecer. Finalmente, mostramos através de dois exemplos a relação entre o efeito Zeno e a decoerência. / We study the quantum decoherence process in different contexts. In particular, we study decoherence effects in the dynamics of a two-level system coupled to another system which has a continuous energy spectrum. We also investigate when the master equation description, in a Born Markov approximation reproduces the exact solution. We extend this investigation to the model which describes the interaction between a harmonic oscillator and a thermal bath of harmonic oscillators in the rotating wave approximation. We also study the two atom correlation scheme originally proposed by Davidovich, Brune, Raimond and Haroche for measuring the decoherence of a mesoscopic superposition of coherent states of a QED cavity in the context of quantum computation. We show that this experiment is equivalent to a quantum computer solving Deutsch\'s problem. We find a way to reduce the errors due to decoherence. Finally, we show how the Zeno effect is related to the decoherence process.

Optimering av prestanda görs på FEM ½” koppling på Parker Hannifin AB med hjälp av finita element analyser (FEA). De kritiska komponenterna som är styrningen, kulhållaren och nippelhuset är i fokus. En noggrannare materialanalys genomförs för att få mer verklighetbaserande materialdata på kopplingen.  Hela nippelhuset antas härdas efter varit i kontakt med företaget som utför härdningen på komponenten. För att få mer information om materialdata utförs statiska trycktester på en koppling. De uppmätta töjningarna från testerna jämförs med töjningarna i simuleringarna. Sträckgränsen och hårdnadskoefficienten på styrningen och kulhållaren kan justeras något från testerna men resultatet har flera osäkerheter.  Antalet kulor i kopplingen mellan 15 och 12 kulor undersöks efter önskemål från företaget. Analyser om hur en härdning påverkar styrningen görs samt hur nippelhuset påverkas av en ythärdning i form av sätthärdning. Vid härdning av styrningen uppkom de minsta deformationerna och spänningarna. Kulhållaren visade tydligt på mindre deformationer och spänningar om antalet kulor minskas från 15 till 12 kulor i kopplingen. För att minska kulintrycket på nippelhuset rekommenderas att ythärda komponenten med en 27 % hårdare yta än den nuvarande. På grund av uppskattade värden på materialdata på ythärdningen behöver mer information införskaffas. Detta för att kunna avgöra vilken tjocklek på ytans härdning som krävs för 12 kulor i kopplingen. / Optimizing the burst pressure with finite element analysis is done on the FEM ½” coupling at Parker Hannifin AB. The critical components which is the ball cage, guide and plug housing are in focus. A more accurate material analysis is done to make a more real-based data of the material in the coupling.   After being in contact with the company that performs the hardening of the component, the entire plug housing is assumed to be hardened. For more information about material data, static pressure test is performed on a coupling. The measured strains from the tests are compared to the strains in the simulations. The tensile strength and hardness coefficient on the guide and ball cage can be adjusted slightly from the tests, but the result has several uncertainties.  The number of balls can be reduced, numbers of balls between 15 and 12 are investigated at request from the company. Analysis of how hardening of the material for the guide is done and hardening of the surface for the plug housing.  The smallest deformation occurs when hardening the guide. The ball cage clearly demonstrated minor deformations and stresses as the number of balls is reduced from 15 to 12 balls in the coupling. To reduce the burst pressure on the plug housing, it is recommended to harden the surface with a 27 % harder surface than the current. Due to estimated values of material data on hardened surface, more information is needed to determine the thickness needed on the surface of the hardening when having 12 balls in the coupling.

Lai Chi-fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 98-99). / Abstracts in English and Chinese. / Chapter 1. --- INTRODUCTION --- p.7 / Chapter 1.1 --- Motivations and objectives --- p.7 / Chapter 1.2 --- Thesis Organization --- p.10 / Chapter 2. --- related works --- p.11 / Chapter 2.1 --- Deformation Techniques --- p.11 / Chapter 2.1.1 --- Deformation techniques requiring a deformation tool --- p.11 / Chapter 2.1.2 --- Directly specified deformation techniques --- p.14 / Chapter 2.1.3 --- Comparison on Different Deformation Technique --- p.15 / Chapter 2.2 --- Application of Deformation --- p.16 / Chapter 2.2.1 --- Deforming superquadrics --- p.16 / Chapter 2.2.2 --- Volume wraping --- p.16 / Chapter 2.2.3 --- Deforming linear object --- p.17 / Chapter 2.2.4 --- FFD for animation synthesis --- p.17 / Chapter 2.2.5 --- Using FFD on feature-based Surface --- p.18 / Chapter 2.2.6 --- NURBS-BASED Free-Form Deformation (NFFD) --- p.18 / Chapter 2.3 --- Algebraic Patch Techniques --- p.20 / Chapter 2.3.1 --- Dahmen's scheme --- p.20 / Chapter 2.3.2 --- Lodha and Warren's technique --- p.20 / Chapter 2.3.3 --- Guo's method --- p.21 / Chapter 3. --- BACKGROUND THEORIES --- p.22 / Chapter 3.1 --- Algebraic Patches --- p.22 / Chapter 3.1.1 --- Bernstein-Bezier representation of a single patch --- p.22 / Chapter 3.1.2 --- Constructing free-form objects --- p.29 / Chapter 3.1.2.1 --- Bounding volumes for quadric patches --- p.29 / Chapter 3.1.2.2 --- Filling two-sided gaps --- p.31 / Chapter 3.2 --- Constructive Shell Representation --- p.35 / Chapter 3.2.1 --- Properties of quadric patches and its construction tetrahedron and trunctets --- p.38 / Chapter 3.3 --- Free-Form Deformation --- p.40 / Chapter 3.3.1 --- Formulating free-form deformation --- p.40 / Chapter 4. --- FREE-FORM DEFORMATION OF CSR SOLID MODELS --- p.43 / Chapter 4.1 --- Determination of Lattice Structure --- p.43 / Chapter 4.2 --- "Relation between weights, normals and shape of a trunctet" --- p.46 / Chapter 4.3 --- Applying FFD on CSR solid models --- p.49 / Chapter 4.3.1 --- Deforming normal at vertices --- p.52 / Chapter 4.3.2 --- Using vertices' neighborhoods --- p.54 / Chapter 4.4 --- Free-Form Deformation of CSR objects by Surface Fitting --- p.57 / Chapter 4.4.1 --- Deforming a single surface patch --- p.57 / Chapter 4.4.1.1 --- Locating surface points --- p.59 / Chapter 4.4.1.2 --- Conversion between barycentric and Cartesian coordinates --- p.61 / Chapter 4.4.1.3 --- Evaluating the deformed surface patch --- p.62 / Chapter 4.4.1.4 --- Saddle shape trunctet --- p.64 / Chapter 4.4.1.5 --- Using double tetrahedrons --- p.66 / Chapter 4.4.1.6 --- Surface subdivision --- p.69 / Chapter 4.4.2 --- Deforming Entire Solid Model --- p.72 / Chapter 4.4.3 --- Comparison on different approaches --- p.75 / Chapter 4.5 --- Conversion of CSG solid Models into CSR --- p.76 / Chapter 4.5.1 --- Converting halfspaces into CSR objects --- p.77 / Chapter 5. --- IMPLEMENTATION AND RESULTS --- p.82 / Chapter 5.1 --- Implementation --- p.82 / Chapter 5.2 --- Experimental Results --- p.84 / Chapter 6. --- CONCLUSION AND SUGGESTIONS FOR FURTHER WORK --- p.93 / Chapter 6.1 --- Conclusion --- p.93 / Chapter 6.2 --- Suggestions for further work --- p.96

Considering the gap in available information and the need of the industries such as oil and gas production, energy, and food processing, this study focuses on the two phase flows around bends in process pipe lines. The aim of this study is to investigate the influence of 90° bends on the gas-liquid two phase flow behaviour in vertical and horizontal orientations using advanced two-phase flow measuring techniques. An experimental study has been conducted using silicone oil with a viscosity of 5 mPa.s and air to examine the transitional flows around 90° bends of 68 mm internal diameter (ID) with different configurations. Experiments were conducted at ambient conditions in an open system which consists of a 68 mm ID riser of 4.5 m long, vertical upward 90° bend and two horizontal sections of a 9.2m and 5.5m long in series with a horizontal 90° bend in between. The experimental matrix comprises 60 combinations of gas and liquid superficial velocities, ranging from 0.045 m.s-1 to 3.21 m.s-1 and 0.15 m.s-1 to 0.53 m.s-1 respectively. The phase distributions within the pipes were measured using Electrical Capacitance Tomography (ECT) and Wire Mesh Sensors (WMS). The behaviour of the flow was examined qualitatively using high speed imaging. To study the flow development in the riser, both ECT and WMS were placed in series and moved along three axial locations downstream of the mixing section. During the experiments at the bends, the ECT was kept immediately upstream while the WMS was moved to different positions downstream of the bend. The cross-sectional void fraction time series from the ECT and the WMS were used to quantify the main hydrodynamic parameters of the flow including cross-sectional averaged void fraction, bubble size distribution, radial void fraction profiles, slug length, slug frequency, void fraction in liquid slugs, and the slug bubble velocity. Results were compared against the available slug flow correlations. The results show that the phases separate shortly after the vertical to horizontal bend leading to stratified or wavy stratified flow. Beyond a certain threshold of the gas flow rate and liquid level, onset of slugs can be observed at a certain distance downstream of the vertical upward bend. This work suggests that the formation of hydrodynamic slugs downstream of the vertical upward bend is independent of the inlet conditions upstream. The horizontal bend, unlike the vertical upward bend, has a minor influence on the flow evolution, particularly slug flow. This is due to the influence of gravitational force on phase separation and its subsequent effect on the change of momentum in the vertical bend. The flow structures, mainly slugs and disturbance waves, are slightly accelerated as they pass through the horizontal bend with minimum change to the structure frequency and gas holdup within liquid slugs. Most of the existing correlations do not predict the measured void fractions in this work as those correlations were essentially limited to the conditions they were developed for as the basis of them lies in the curve fitting. In this work, the higher viscosity and lower surface tension led to higher gas holdup in liquid slugs causing the discrepancy.

This thesis is concerned with the study of two independent problems. Chapter 2 is devoted to the development of a new representation for the dynamic Green's tensor for a layered medium. No completely closed solution is possible and the objective here is to develop a representation that is more amenable to computation than the existing representations (Cagniard (39), Willis (73)). The representation derives from a reduction of the integrals required for the inversion of the terms in a "generalized ray" series. For the three-dimensional (point source) problem the final solution requires either a single integration (isotropic layers) or two integrations (anisotropic layers) over contours that are independent of time t and position x. The integrand is a simple explicit function, much of which is independent of x and t and may be tabulated when the solution is required for a range of values of x and t. The remainder of this thesis examines the time-harmonic response of thin, elastic, fluid-loaded plates stiffened by attached parallel beams. The sound radiated by such structures has been studied by many authors but few have been concerned with the motion of the plate. Chapters 3, 4 and 5 of this thesis examine plates stiffened, respectively, by finite, infinite, and semi-infinite arrays of beams. In chapter 3, Fourier transforms are used to obtain a set of simultaneous equations for the transformed displacements and rotations at the beams. The inverse transform of the solution to this set of equations is evaluated asymptotically. In chapters 4 and 5 the stiffening beams are equally spaced. The equations are formulated in terms of discrete convolutions and a transform, related to the modified Z-transform, is used (together with the Wiener-Hopf technique in chapter 5) to obtain the solution. Asymptotically, the motion of the stiffened regions of the plate has the form of a Floquet wave.

This study is concerned with a variable geometry inward flow radial turbine for turbocharging Diesel engines. A detailed theoretical and experimental investigation in both the stator and rotor is presented. The finite element method being applied for the flow analysis. The finite element procedure was initially developed by applying it to an isolated aerofoil prior to the further application to cover a circular cascade of blades as encountered in the volute-nozzle assembly. In the rotor, only the hub-shroud analysis was carried out and the results compared with an existing streamline curvature technique. It was shown that the finite element method required less computaional time and was more generally applicable to complex geometric configurations than the streamline curvature technique. Experimentally, the turbine performance was evaluated with and without exhaust diffusers and with a number of nozzle rings with different restrictions. It was shown that the maximum restriction resulted in high losses due to the flow mismatching at nozzle inlet because of the sudden area change, and relatively low efficiencies resulted. The effect of swirl, resulting from off-design operation, on the diffusers was analysed with three conical diffusers. The results show that low swirls of the order of 10%, has a beneficial effect on the pressure recovery coefficient for wide angle diffuser.

Thesis. 1977. B.S.--Massachusetts Institute of Technology. Dept. of Physics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 66-68. / B.S.

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