<p>Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily by the flexible printing plate and the low viscosity inks which make it suitable for use on almost any substrate. The object of this study was to obtain further knowledge of the some important mechanisms of flexographic printing and how they influence the print quality. The thesis deals with printing primarily on board and liner but also on newsprint with water-borne ink using a full-scale flexographic central impression (CI) printing press. Several printing trials have been performed with a focus on the chemical interaction between the ink and substrate and the physical contact between the ink-covered printing plate and the substrate.</p><p>Multicolour printing exposes the substrate to water from the water-containing ink. The emphasis was to investigate the relation between print quality and water-uptake of the paper surface with heat and water. Printing trials was carried out on substrates possessing a hydrophobic, and also a rather hydrophilic surface using a regular commercial water-borne ink. The favorable effect which water or surfactant solution had on the hydrophobic substrate with regard to print mottle could depend on its surface compressibility in combination with the hydrophobic nature of its surface that could affect the wetting properties.</p><p>Conventional printing involves physical contact between plate and ink and between ink and substrate. A method for measuring the dynamic nip pressure using thin load cells is presented. Print quality was influenced by the plate material. A correction procedure taking into account the size of the sensor was developed in order to estimate the maximum dynamic pressure in the printing nip. An attempt was made to identify essential mechanical and chemical parameters, and also geometrical properties of the plate that affected print quality. Laboratory printing trials were carried out and a multivariate analysis was applied for evaluation of print quality data. The impact of the plate properties on print quality was evident. The essential properties of the plate that influence print quality were the small-scale roughness and long-scale roughness.</p>

The Oregon State University (OSU), Hydro Mechanical Fuel test Facility (HMFTF) is designed to hydro-mechanically test prototypical plate type fuel. OSU's fuel test program is a part of the Global Threat Reduction Initiative (GTRI), formerly known as the Reduced Enrichment for Research and Test Reactor program. One of the GTRI's goals is to convert all civilian research, and test reactors in the United State from highly enriched uranium (HEU) to a low enriched uranium (LEU) fuel in an effort to reduce nuclear proliferation. An analytical model has been developed and is described in detail which complements the experimental work being performed by the OSU HMFTF, and advances the science of hydro-mechanics. This study investigates two methods for determining the critical flow velocity for a pair of laminated plates. The objective is accomplished by incorporating a flexural rigidity term into the formulation of critical flow velocity originally derived by Miller, and employing sandwich structure theory to determine the rigidity term. The final outcome of this study results in the developing of a single equation for each of three different edge boundary conditions which reliably and comprehensively predicts the onset of plate collapse. The two models developed and presented, are termed the monocoque analogy and the ideal laminate model. / Graduation date: 2013

High pressure applications are alternatives to conventional methods in food processing. They provide interesting modifications in food structures which leads to new product formulations. The aim of this study is to identify the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP) on stability and rheological properties of model oil-in-water emulsions. Microfluidization was selected among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared to the coarse emulsions which were prepared with colloid mill homogenization. Stability of emulsions was determined comparatively by using an analytical photo-centrifuge device employing a novel analysis technology. Whey protein isolate (WPI) was used as an emulsifier in combination with a food polysaccharide as a stabilizer. The polysaccharides used were xanthan gum, guar gum and locust bean gum which are widely used stabilizing ingredients in food industry. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities. The finer emulsions obtained with this homogenization technique led to distinctive improvements in emulsion stability. On the other hand, the improvements in stability by HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations with higher oil content. Apart from these, HHP treatment was found to be relatively more contributing to the enhancements in viscoelastic properties.

Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily by the flexible printing plate and the low viscosity inks which make it suitable for use on almost any substrate. The object of this study was to obtain further knowledge of the some important mechanisms of flexographic printing and how they influence the print quality. The thesis deals with printing primarily on board and liner but also on newsprint with water-borne ink using a full-scale flexographic central impression (CI) printing press. Several printing trials have been performed with a focus on the chemical interaction between the ink and substrate and the physical contact between the ink-covered printing plate and the substrate. Multicolour printing exposes the substrate to water from the water-containing ink. The emphasis was to investigate the relation between print quality and water-uptake of the paper surface with heat and water. Printing trials was carried out on substrates possessing a hydrophobic, and also a rather hydrophilic surface using a regular commercial water-borne ink. The favorable effect which water or surfactant solution had on the hydrophobic substrate with regard to print mottle could depend on its surface compressibility in combination with the hydrophobic nature of its surface that could affect the wetting properties. Conventional printing involves physical contact between plate and ink and between ink and substrate. A method for measuring the dynamic nip pressure using thin load cells is presented. Print quality was influenced by the plate material. A correction procedure taking into account the size of the sensor was developed in order to estimate the maximum dynamic pressure in the printing nip. An attempt was made to identify essential mechanical and chemical parameters, and also geometrical properties of the plate that affected print quality. Laboratory printing trials were carried out and a multivariate analysis was applied for evaluation of print quality data. The impact of the plate properties on print quality was evident. The essential properties of the plate that influence print quality were the small-scale roughness and long-scale roughness.

[pt] Experimentos referentes ao movimento relativo entre partículas sólidas e um fluido viscoso confinado no interior de cilindros de seção reta arbitrária (circular, quadrangular) foram realizados. Para todos os casos experimentalmente investigados e, para escoamentos variando desde regimes de muito baixo Números de Reynolds (Re menor que 0,1) até um regime bem além do regime de Oseen, constatou-se que a razão entre a força de pressão e a força de arrasto viscoso (Delta P mais A/D) pode ser diretamente medida através de parâmetros do escoamento não perturbado (escoamento em ausência da partícula). De acordo com uma recente teoria (Brenner, 1962) a afirmativa acima que se baseia em uma linearização do tipo Oseen das equações de movimento, deveria apenas ser esperada para regimes de baixos Números de Reynolds (Re menor que 2). Brenner (1962), utilizando-se dos teoremas de momentum e energia, aplicados ao movimento relativo de uma partícula sólida e um fluido viscoso confinado por paredes sólidas, mostrou que, devido ao movimento relativo, uma força de cisalhamento atuando nas paredes do cilindro deve necessariamente existir, ainda que estas paredes estejam infinitamente distantes da perturbação induzida pela partícula. A generalidade da Teoria de Brenner, relativa à geometria da seção reta do cilindro, foi também verificada nos regimes de Stokes e de Oseen. Experimentos realizados em uma coluna curta (1 m) de seção reta circular forneceram um conjunto de dados que foram utilizados para se qualificar, a um baixo nível de incerteza experimental, a técnica experimental utilizada. Experimentos realizados em uma coluna longa (3 m) de seção reta quadrangular permitiram a verificação da teoria em regimes distantes do regime teórico. Medidas da diferença de pressão adicional induzida pelo movimento relativo entre a partícula e o líquido viscoso confinado no duto de seção quadrangular, claramente definiram três diferentes regiões: i) até Re~50, verificou-se que a razão Delta P+A/D aproximadamente 2,093, resultado este que deveria ser esperado apenas para Re < 2,0. Por consideração elementares de momentum aplicáveis a um volume de controle constituído do fluido viscoso no entorno da partícula, pode-se facilmente mostrar que o valor Delta P+A/D diferente de 1,0 confirma a existência de uma força de cisalhamento finita atuando nas paredes do duto infinitamente distantes da partícula; ii) além de Re ~ 50, uma transição abrupta se inicia forçando o valor Delta P+A/D a decrescer. A razão de força Delta P+A/D decresce assintoticamente para o valor 1,0, valor este que corresponde à situação de um fluido ilimitado (meio contínuo fluido sem fronteiras) conforme prescrito pelo Princípio de Momentum; iii) para Re > 2500, a razão Delta P+A/D fortemente aproxima-se do valor 1,0. O maior regime investigado foi Re ~ 36000 mas, fisicamente, não parece existir nenhum argumento que possa contradizer a permanência do comportamento acima descrito. Este trabalho discute também um método bastante preciso conduzindo à medição do arrasto viscoso sobre a partícula e também uma técnica para se medir as pequenas quedas de pressão(~ 1 a 10 elevado à -3 mm Hg) induzidas pelo movimento da partícula. / [en] Experiments concerning the relative motion of solid particles and viscous fluids, confined within cylinders of arbitrary cross-section (circular and quadrangular) have been conducted. For all cases experimentally investigated and for a flow regime extending from a very low particle Reynolds Number (Re less than 0.1) up to far beyond the Oseen s Regime, it has been shown that the additional pressure force to viscous drag ratio (Delta plus A/D) can be directly evaluated by means of parameters of the unperturbed flow. Accordingly to a recent theory (Brenner, 1962) the above statement which uses a Oseen s type linearization of the equation of motion, should only be expected for the very low particle Reynolds Number regime (Re < 2). Brenner (1962), using momentum and energy theorems applied to the relative motion of a particle and a confined viscous fluid has shown that, as a result of the relative motion, a finete shearing force acting on the cylinder walls must existis, even if the walls are infinitely distant from the particle perturbation. The generality of Brenner s theory concerning the cylinder geometry was also verified in the Stokes and in the Oseen s regimes. Experiments conducted in a short (1 m) circular cylinder, filled with a Newtonian fluid, provided the base line data set used to qualify the experimental technique used, within very low experimental uncertainties. Experiments conducted in a long square cylinder (3 m), allowed verification of the theory far beyond the theorectical regime. Measurements of the additional pressure drop created by the relative motion between a solid particle and the viscous fluid, confined in the square cylinder, cleary defined three regions: i) up to about Re ~ 50 it was found that the pressure force to Viscous drag ratio Delta P+A/D approximately 2.093 which should be expected only for Re < 2. By elementary momentum considerations, applied to the fluid control volume around the particle present in the flow, it can easily be show that this value of Delta P+A/D diferente than 1 confirms the existence of a finete shearing force on the far walls of the cylinder; ii) beyond Re = 50 and up to Re ~ 2500 a very complex and not completely understood transition occurs. At about Re ~ 50 an abrupt transition takes place forcing the value of Delta P+A/D to decrease. The ratio Delta P+A/D decreases asymptotically towards the value 1.0 wich corresponds to the situation of an unbounded fluid as can be predicted by the Momentum Principle; iii) for particle Reynolds Number Re > 2500, the Delta P+A/D approaches very closely the value 1.0. The largest flow regime investigated was Re ~ 36000 but, physically, there seems to be no reason to expect any change in the described behaviour. This work also discusses an accurate method for directly measuring the viscous drag force and the diminute dynamic pressure (~ 1 to 10 (-3) mm Hg) created by the motion of the particle.

For the supersonic flow mode, which occurs in the internal flow behind the aperture separating two spaces with a large pressure drop, the critical flow is a characteristic phenomenon. In the case of critical flow behind the aperture, a supersonic flow area with reduced pressure ending with a shock wave with a step change in state variables is created. When diagnosing velocities, which are obtained from the values of static and total pressure, due to the changes caused by the shock wave passage, correction of the diagnostic quantities obtained by measuring by means of mathematical relations taking into account the physical phenomena is necessary.

This thesis is based on the series of scholarly article dedicated to the issue ofpumping in the differential scanning chamber of an environmental scanning microscope. The thesis is based on Danilatos’s study where the pumping of the differential pumped chamber is solved by means of the Monte Carlo statistical method. The thesis performs analysis of gas flow at low pressures through orifice separating the spaces with a large pressure drop Dr. Danilate. The analyses will be used for the design of the experimental chamber which will serve for the experimental evaluation of the flow results in the chamber using the continuum mechanics.

[pt] Uma análise numérica de escoamento anular vertical ascendente é realizada utilizando o Modelo de Dois Fluidos unidimensional. Para escoamentos verticais, na ausência de mecanismos estabilizadores, o sistema de equações resultante é incondicionalmente mal posto. Dessa forma, visando tornar o sistema de equações bem posto, adicionou-se às equações de quantidade de movimento um termo de pressão dinâmica. Dois modelos disponíveis na literatura são investigados. O primeiro só considera a pressão dinâmica na equação de quantidade de movimento do líquido, a qual é baseada em uma simples expressão para a velocidade da onda na interface. O segundo modelo inclui uma contribuição da pressão dinâmica em ambas equações de quantidade de movimento. No presente trabalho, um terceiro modelo é proposto, o qual é baseado no primeiro modelo, com uma avaliação mais realista da velocidade da onda na interface. O efeito estabilizante da pressão dinâmica é demonstrado através de um rigoroso teste de convergência de malha. As equações de conservação são discretizadas com o método de volumes finitos, com uma integração temporal de primeira ordem e uma discretização espacial TVD de segunda ordem. Tanto o segundo quanto o terceiro modelo considerados apresentaram solução independente da malha. Parâmetros do escoamento como gradiente de pressão, espessura do filme, e variáveis características da onda obtidos numericamente são comparados com dados experimentais disponíveis na literatura, apresentando boa concordância. / [en] A numerical analysis of vertical ascending annular flow with the 1D Two-Fluid model is performed. It is well known that, in vertical flows, the resulting system of equations is unconditionally ill-posed in the absence of stabilizing mechanisms. Therefore, in the present work, to render the system of equations well-posed, modeling of dynamic pressure is included in the momentum equations. Two models available in the literature are examined. The first one only considers the dynamic pressure in the liquid momentum equation, which is based on a simple expression for the interface wave velocity. The second model includes a dynamic pressure contribution to both momentum equations. A third model is proposed based on the first, with a more realistic estimation of the interface wave velocity. A systematic grid convergence test is performed to demonstrate the stabilizing effect of the dynamic pressure. The conservation equations are discretized with the finite volume method, with a first order time integration, and a second order TVD spatial discretization. A grid-independent solution can be found when applying the second and third models considered. Flow parameters such as pressure drop, film thickness and wave characteristics numerically obtained are compared against available experimental data, presenting good agreement.

Für die Untersuchung von Luft/Wasser-Strömungen wurde ein horizontaler Acrylglas-Kanal mit rechteckigem Querschnitt gebaut. Der Kanal ermöglicht Gleich- und Gegenstrom-Versuche bei Atmosphärendruck, insbesondere die Untersuchung der Schwallströmung. Es wurden optische Messungen mit einer Hochgeschwindigkeits-Kamera durchgeführt, die durch synchronisierte dynamische Druckmessungen ergänzt wurden. Für die Analyse der Bilder wurde eine Methode zur Erfassung der Phasengrenze entwickelt und diese anhand möglicher Anwendungen getestet. Die Druckmessungen zeigten, dass der Druck bei Schwallströmungen um einige Kilopascal ansteigt und wieder abfällt, sobald der Schwall aus dem Kanal austritt. Zudem wurden Geschwindigkeiten in der flüssigen Phase mittels nicht invasiver Verfahren gemessen. Das durchschnittliche Geschwindigkeits-Profil am Kanaleintritt wurde mit Ultraschall-Köpfen bestimmt. Die Ermittlung des Geschwindigkeitsfeldes in einem Schwall erfolgte mit PIV (Particle Image Velocimetry).

Für die Untersuchung von Luft/Wasser-Strömungen wurde ein horizontaler Acrylglas-Kanal mit rechteckigem Querschnitt gebaut. Der Kanal ermöglicht Gleich- und Gegenstrom-Versuche bei Atmosphärendruck, insbesondere die Untersuchung der Schwallströmung. Es wurden optische Messungen mit einer Hochgeschwindigkeits-Kamera durchgeführt, die durch synchronisierte dynamische Druckmessungen ergänzt wurden. Für die Analyse der Bilder wurde eine Methode zur Erfassung der Phasengrenze entwickelt und diese anhand möglicher Anwendungen getestet. Die Druckmessungen zeigten, dass der Druck bei Schwallströmungen um einige Kilopascal ansteigt und wieder abfällt, sobald der Schwall aus dem Kanal austritt. Zudem wurden Geschwindigkeiten in der flüssigen Phase mittels nicht invasiver Verfahren gemessen. Das durchschnittliche Geschwindigkeits-Profil am Kanaleintritt wurde mit Ultraschall-Köpfen bestimmt. Die Ermittlung des Geschwindigkeitsfeldes in einem Schwall erfolgte mit PIV (Particle Image Velocimetry).