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MEMS (Micro Electro Mechanical Systems) have received a great deal of attention in both the research and industrial sectors in recent decades. The broad MEMS category, microfluidics, the study of fluid flow through channels measured on the micrometer scale, plays an important role in devices such as compact heat exchangers, chemical and biological sensors, and lab-on-a-chip devices. Most of the research has been focused on how entire systems operate, both experimentally and through simulation. This paper strives, systematically, to map them through experimentation of the previous to untested realm of pressure loss through laminar square-profile sweeping-bend microchannels. Channels were fabricated in silicone and designed so a transducer could detect static pressure across a very specific length of channel with a desired bend. A wide variety of Reynolds numbers, bend radii, and bend angles were repeatedly tested over long periods in order to acquire a complete picture of pressure loss with in the domain of experimentation. Nearly all situations tested were adequately captured with the exception of some very low loss points that were too small to detect accurately. The bends were found to match laminar straight-duct theory at Reynolds numbers below 30. As Reynolds numbers increased, however, minor losses began to build and the total pressure loss across the bend rose above straight-duct predictions. A new loss coefficient equation was produced that properly predicted pressure losses for sweeping-bends at higher Reynolds numbers; while lower flow ranges are left to laminar flow loss for prediction.

<p>Flow Accelerated Corrosion (<em>FAC</em>) is defined as a flow enhanced mass transfer phenomenon that results in pipe wall thinning of the piping system and results in abrupt failure in some cases. <em>FAC</em> is controlled by the transport of corrosion species from the wall to the bulk fluid and is determined by the local distribution of the mass transfer coefficient. The overall objective of this research is to investigate the mass transfer in pipe bends arranged in single and dual S- shape configurations under single and annular two phase flow conditions. A novel wall dissolving mass transfer technique was developed to measure the local mass transfer distribution under a Schmidt number (<em>Sc</em>) of 1280, which mimics the level of carbon steel in water in industrial applications. Flow field measurements using Particle Image Velocimetry (<em>PIV</em>) and flow visualizations using laser induced fluorescence were performed to understand the causal relation between the mass transfer and the flow dynamics.</p> <p>The mass transfer in single 90^o bends under single phase flow was measured for a range of <em>Re</em> from 40,000 to 130,000. Three regions of elevated mass transfer rates were determined in the single bend, (i) near the inlet to the bend inner wall, (ii) midway on the bend inner wall sides and (iii) near the outlet of the bend outer wall. The maximum mass transfer enhancement relative to the upstream pipe was found to occur near the outlet of the single bend outer wall and spans over the first part of the downstream pipe with a magnitude of approximately 1.8. The surface roughness of the test sections were determined at the end of each experiment and found to be in the fully rough wall region. The mass transfer coefficient at the high mass transfer locations was found to scale as <em>Re</em>^0.92. The maximum enhancement was found to be independent of <em>Re</em> for the range of <em>Re</em> studied here.</p> <p>For the dual S- shape bends, tests were performed for different separation distances <em>L/D</em> of 0, 1 and 5. The <em>L/D</em>=0 case were tested for a range of <em>Re</em> from 40,000 to 130,000. The maximum mass transfer enhancement relative to the upstream pipe was found to occur when there was no separation distance between the bends. This maximum occurred at the transition from the first bend outer wall to the second bend inner wall with a magnitude of approximately 3.2. The mass transfer enhancement was found to decrease when the separation distance between the two bends was increased. A second region of high mass transfer enhancement was found to occur midway on the second bend inner wall in the form of two symmetric regions shifted from the centerline with a magnitude of 2.8.</p> <p>The effect of air and water superficial velocities for annular flow in the range of <em>J_v</em>= 22- 29.5 m/s, and <em>J_L</em>= 0.17- 0.41 m/s on the mass trasnfer in single and dual S- shape bends was determined. The maximum mass transfer was found to occur midway on the centerline of the bend outer wall for the single bend case. This location corresponded to the entrained liquid droplet impingment and anticipated high velocity region due to liquid film thining. A second high mass transfer region was observed on the latter part of the bend outer wall. The effect of the air superficial velocity on the mass transfer enhancement was more significant than the effect of the water superficial velocity.</p> <p>The maximum mass transfer enhancement in the S- shape bend geometry under annular two phase flow was found to always occur on the first bend outer wall at a similar location to the single bend case. The mass transfer in the second bend was lowest for the zero separation distance between the bends, and increased with an increase in the separation distance. The maximum mass transfer in the second bend occurred near the outlet of the second bend outer wall with a magnitude of approximately 60% of that in the first bend when the separation distance was zero. The maximum mass transfer in the second bend was found to increase with an increase in separation distance to reach approximately 85% of that in the first bend for <em>L/D</em>=40. The location of the maximum region was observed to shift in the upstream direction as the separation distance was increased to approach the location of the single bend maximum near <em>L/D</em>=40.</p> <p>Flow field measurements showed matching of the areas with high mean flow velocity on the inlet portion of the single bend inner wall. The high velocity stream was observed to shift toward the outer wall near the bend outlet. Similar features were observed in the first bend of the S- shape configuration. The flow velocity increased significantly near the transition from the first bend outer wall to the second bend inner wall of the dual S-shape bend. High turbulent kinetic energy was measured near the outlet of the single bend outer wall and inner wall. Similar kinetic energy distribution was observed on the first bend of the S- shape. The turbulent kinetic energy downstream of the first bend increased to approximately twice that in the first bend and was observed to travel from the outlet of the first bend inner wall to the second bend inner wall. For two phase annular flow, the phase redistribution visualization showed liquid separation from the core flow and deposition on the bend wall. Three locations of deposition were observed (a) on the first bend outer wall near <em>ϕ</em>₁ of 50^o, (b) between the 50^o and the outlet of the first bend (c) on the latter part of the second bend outer wall.</p> / Doctor of Philosophy (PhD)

The tallest mountain in North America, Mount McKinley is situated inside a sharp bend in the right‐lateral Denali fault. This anomalous topography is clearly associated with the complex geometry of the Denali fault, but how this topography evolves in conjunction with the adjacent strike‐slip fault is unknown. To constrain how this fault bend is deforming, the Quaternary fault‐related deformation on the opposite side of the Denali fault from Mount McKinley were documented through combined geologic mapping, active fault characterization, and analysis of background seismicity. My mapping illustrates an east‐west change in faulting style where normal faults occur east of the fault bend and thrust faults predominate to the west. These faults offset glacial outwash terraces and moraines which, with tentative correlations with the regional glacial history, provide fault slip rates that suggest that the Denali fault bend is migrating southwestward. The complex and elevated regional seismicity corroborates the style of faulting associated with the fault bend and provide additional subsurface control on the location of active faults. Seismologic and neotectonic constraints suggest that the maximum compressive stress axis rotates from vertical east of the bend to horizontal and Denali fault‐normal west of the bend.

Rivers are considered as one of the most important surface water resources on the earth. During the time, most of the rivers on the earth experienced evolution and changes. River bends and confluences are one of the common cases in most rivers. There is a significant impact of the flow on the cross-sectional profile of river bends and confluences. Secondary currents are one of the important features that characterize flow in river bends and confluences. In such currents, fluid particles follow a helical path instead of moving nearly parallel to the axis of the channel. The local imbalance between the vertically varying centrifugal force and the cross-stream pressure gradient results in generating the secondary flow and raising a typical motion of the helical flow. Several studies, including experimental or mathematical, have been conducted to examine flow characteristics in curved open channels, river meanders, or confluences. In this research, the influence of secondary currents is studied on the elevation of water surface and the hydraulic structures in channel bends and confluences by employing a 3D OpenFOAM numerical model. The research implements a 3D OpenFOAM numerical model to simulate the horizontal distribution of the flow. In addition, the progress in unraveling and understanding the bend and confluent dynamics is discussed. The finite volume method in OpenFOAM software is used to simulate and examine the behavior of the secondary current. Thereafter, a comparison between the experimental data and a numerical model is conducted. Two sets of experimental data are used as the dataset for these two experiments are complete and validated; the data provided by Rozovskii (1961) for a sharply curved channel, and the dataset provided by Shumate (1998) for a confluent channel. Two solvers in OpenFOAM software were selected to solve the problem regarding the experiment: InterFoam and PisoFoam. InterFoam is a transient solver for incompressible flow that is used with open channel flow with Free Surface Model. PisoFoam is a transient solver for incompressible flow that is used with closed channel flow and Rigid-Lid Model. Various turbulence models (i.e., Standard k-ε, Realizable k-ε) are applied in the numerical model to assess the accuracy of turbulence models in predicting the behavior of the flow. The accuracies of various turbulence models are examined and discussed.

Multiphase flows occurring in pipelines with a serpentine configuration is an important phenomenon, which can be encountered in heat exchangers used in a variety of industrial processes. More specifically, in many industrial units such as a large cracking furnace in a refinery, the tubes are arranged in a serpentine manner and are relatively short. As flow negotiates round the 180o bend at the ends of the tubes, the generated centrifugal force could cause flow maldistribution creating local dry spots, where no steady liquid film is formed on the adjacent straight sections of the pipe. As a result, events including coking, cracking and overheating of heat transfer surfaces may occur and lead to frequent shutdown of the facilities. Consequently, this could increase operating costs and reduce production revenue. Thus, it is desirable to know the effect that the bends exert on the flow in the straight part of the pipe. Apart from this, knowledge of the bend effects on the flows in the pipeline could also be important for the design of other pipelines for gas/liquid transport, e.g. offshore gas and oil pipelines. Quite a large number of studies have been found in the literature. The majority of them were for two-phase flow with small diameter pipes (i.d. ≤ 50 mm). However, studies with large diameter pipes (i.d. ≥ 100 mm), have increasingly been considered in recent years as problems related to large diameter vertical pipes are being encountered more and more often in industrial situations. This thesis studies the effect of 180o bends on the characteristics and development of gas-liquid two-phase flows in large diameter downward and upward pipes. The study particularly focuses on the influence of serpentine configuration on flow structure, cross-sectional void distribution and circumferential liquid film profiles and their development along the downward and upward sections. It was found that both the top and bottom bends have considerable impacts on flow behaviour, although to varying degrees. These impacts were highly dependent on the air and water flow rates. For sufficient flow rates, the bends were observed to create flow maldistribution in the adjacent straight section, due to the effects of centrifugal force. The air moved towards the inner zone of the bend and the water towards the outer zone, while a lesser quantity of water was identified on the other surfaces of the pipe. Investigation of the film thickness development in the downward and upward sections showed that, the liquid film behaviour close to the bends was significantly different from those located further away. This can be attributed to the centrifugal force of the bends. Examination of the power spectral density (PSD) along the downward and upward sections showed that, the shape of PSD located in the adjacent section to the bends, was substantially different from those located further away. Furthermore, several flow regime maps were generated which showed that, in addition to bubbly, intermittent and annular flows, unstable flows existed along the upward section, particularly for low gas and water flow rates. In this study it was found that, the lower bend was periodically blocked by the liquid and then blown through by the accumulated air. The data obtained from this study were compared with different theoretical correlations found in the existing literature. Some discrepancy between the results of the current study and those of previous published materials was noted. Updated correlations were presented which provided well results when they applied for the data obtained from the current study and previous studies.

En plongée, lors d’une décompression, une partie des gaz dissous dans l’organisme est éliminée sous formede bulles qui peuvent être à l’origine d’accidents parfois sévères. Des modèles mathématiques permettentde déterminer des procédures de décompression par paliers fiables mais ne s’appliquent que pour certainesconfigurations de plongée (profondeur, durée, gaz respirés). Une extrapolation de ces modèles à denouveaux types d’exposition comme la plongée profonde aux mélanges est actuellement hasardeuse. Onsuppose ici qu’une modélisation biophysique des mécanismes de la décompression doit apporter dessolutions préventives plus sures, même pour des expositions moins explorées combinant azote et hélium.Deux modèles ont été élaborés pour la prévention des accidents articulaires et neurologiques, formesd’accident les plus fréquentes. Ils ont été corrélés à partir de bases de données et d’analyses de risqueexistantes. Tous deux permettent de représenter l’apparition de symptômes tardifs. Pour l’accidentarticulaire, on montre 1/ l’impact de la diffusion intra-tissulaire (entre un tendon et son voisinage) de gazinerte sur la dynamique d’amplification de la phase gazeuse générée 2/ une augmentation quantifiable durisque d’accident avec le volume de gaz généré 3/ une faible efficacité des paliers 4/ une efficacité modéréede la respiration d’oxygène pur aux paliers proches de la surface. Pour les accidents neurologiques, lemodèle global proposé permet d’estimer le volume instantané des microbulles formées dans les tissus(muscles et graisses) et transférées (via le système lymphatique par ex) dans le sang veineux de retour. Lasurcharge du filtre pulmonaire par les bulles est supposée être un événement précurseur dans la genèse del’accident. La méthode de corrélation du modèle, originale, utilise notamment des campagnes d’écoutes debulles circulantes par système Doppler après plongées, dont une dédiée à cette thèse. Il ressort de cesinvestigations que I/ le risque d’accident peut être relié au volume des bulles transféré dans le sang sur unepériode donnée II/ l’introduction de paliers profonds ne diminue pas le risque III/ la respiration d’oxygènepur aux paliers est très efficace pour réduire ce risque. Un deuxième modèle neurologique dédié à laprévention des accidents médullaires se produisant rapidement après la décompression et à la déterminationdes premiers paliers requis est aussi proposé. L’ensemble de ces trois modélisations offre des perspectivesde prévention intéressantes. / During a scuba diving decompression, a part of the gas that is dissolved in the body is eliminated throughbubbles that can generate potentially severe forms of decompression sickness (DCS). Known mathematicalmodels allow the determination of safe decompression procedures by stages but can only be applied for alimited range of diving configurations (pressure, duration, breathing gas). An extrapolation of these modelsto new expositions such as deep/short dives using mixtures is currently hazardous. In the presented work itis deemed that a biophysical modeling of the decompression mechanisms can produce safer preventivesolutions even for less explored expositions combining nitrogen and helium. Two models have beendeveloped for the prevention of articular and neurological DCS, which are the most frequent forms ofinjury. Existing database and risk analyses have been used to correlate the models. Both predict potentialdelays for the occurrence of DCS symptoms after a decompression. For the articular model it is shown that1/ the intratissular diffusion of inert gases between a target tendon and its neighborhood impacts theamplification dynamics of the generated gas phase 2/ the more the generated gas volume, the bigger theDCS risk 3/ stages of short and moderate durations have a low efficiency 4/ the efficiency of pure oxygenbreathing in order to reduce the risk during the shallow stages is moderated. For neurological DCS, theproposed global model allows estimation of the instantaneous volume of microbubbles that are formed intissues (muscles and adipose tissues) and that are transferred via the lymphatic system for instance in thevenous blood. The overload of the pulmonary filter by bubbles is assumed to be a primary event in the DCSpathogenesis. The original model correlation method uses in particular the recording of circulating bubblessignals through Doppler detections campaigns. One of these campaigns is dedicated to the presented thesiswork. The analysis leads to the following conclusions: I/ the DCS risk is linked to the total bubbles volumethat is transferred into the blood over a given period II/ the introduction of deep stages does not decreasethe risk III/ the breathing of pure oxygen during the shallow stages is very efficient in reducing this risk. Asecond neurological model is proposed: it is dedicated to the prevention of spinal cord DCS forms whichoccur early after the decompression and to the determination of the first required stops. The threedeveloped models give interesting prevention perspectives.

Understanding how swirl flows can be applied to processes in the oil and gas industry and how problems might hinder them, are the focus of this thesis. Three application areas were identified: wet gas metering, liquid loading in gas wells and erosion at pipe bends due to sand transport. For all three areas, Computational Fluid Dynamics (CFD) simulations were performed. Where available, experimental data were used to validate the CFD results. As a part of this project, a new test loop was conceived for the investigation of sand erosion in pipes. The results obtained from CFD simulations of two-phase (air-water) flow through a pipe with a swirl-inducing device show that generating swirl flow leads to separation of the phases and creates distinct flow patterns within the pipe. This effect can be used in each of the three application areas of interest. For the wet gas metering application, a chart was generated, which suggests the location of maximum liquid deposition downstream of the swirling device used in the ANUMET meter. This will allow taking pressure and phase fraction measurements (from which the liquid flow rate can be determined) where they are most representative of the flow pattern assumed for the ANUMET calculation algorithms. For the liquid loading application, which was taken as an upscaling of the dimensions investigated for the wet gas metering application, the main focus was on the liquid hold-up. This parameter is defined as the ratio of the flowing area occupied by liquid to the total area. Results obtained with CFD simulations showed that as the water rate increases, the liquid hold-up increases, implying a more effective liquid removal. Thus, it was concluded that the introduction of a swirler can help unload liquid from a gas well, although no investigation was carried out on the persistance of the swirl motion downstream of the device. For the third and final application, the erosion at pipe bends due to sand transport, the main focus was to check the erosion rate on the pipe wall with and without the introduction of a swirler. The erosion rate was predicted by CFD simulations. The flow that was investigated consisted of a liquid phase with solid particles suspended in it. The CFD results showed a significant reduction in erosion rate at the pipe walls when the swirler was introduced, which could translate into an extended working life for the pipe. An extensive literature review performed on this topic, complemented by the CFD simulations, showed the need for a dedicated multiphase test loop for the investigation of sand erosion in horizontal pipes and at bends. The design of a facility of this type is included in this thesis. The results obtained with this work are very encouraging and provide a broad perspective of applications of swirl flows and CFD for the oil and gas industry.

Photonic crystals have allowed unprecedented control of light and have allowed bringing new functionalities on chip. Photonic crystal waveguides (PCWs), which are linear defects in a photonic crystal, have unique features that distinguish these waveguides from other waveguides. The unique features include very large dispersion, existence of slow light, and the possibility of tailoring the dispersion properties for guiding light. In my research, I have overcome some of the challenges in using slow light in PCWs. In this work, I have demonstrated (i) high efficiency coupling of light into slow group velocity modes of a PCW, (ii) large bandwidth high transmission and low dispersion bends in PCWs, (iii) accurate modeling of pulse propagation in PCWs, (iv) high efficiency absorbing boundary conditions for dispersive slow group velocity modes of PCWs. To demonstrate the utility of slow light in designing high efficiency devices, I have demonstrated refractive index sensors using slow light in PCWs. In the end, a few high efficiency devices based on slow light in PCWs are mentioned. The remaining issues in the widespread use of PCW are also discussed in the last chapter.

Multiphase flows occurring in pipelines with a serpentine configuration is an important phenomenon, which can be encountered in heat exchangers used in a variety of industrial processes. More specifically, in many industrial units such as a large cracking furnace in a refinery, the tubes are arranged in a serpentine manner and are relatively short. As flow negotiates round the 180o bend at the ends of the tubes, the generated centrifugal force could cause flow maldistribution creating local dry spots, where no steady liquid film is formed on the adjacent straight sections of the pipe. As a result, events including coking, cracking and overheating of heat transfer surfaces may occur and lead to frequent shutdown of the facilities. Consequently, this could increase operating costs and reduce production revenue. Thus, it is desirable to know the effect that the bends exert on the flow in the straight part of the pipe. Apart from this, knowledge of the bend effects on the flows in the pipeline could also be important for the design of other pipelines for gas/liquid transport, e.g. offshore gas and oil pipelines. Quite a large number of studies have been found in the literature. The majority of them were for two-phase flow with small diameter pipes (i.d. ≤ 50 mm). However, studies with large diameter pipes (i.d. ≥ 100 mm), have increasingly been considered in recent years as problems related to large diameter vertical pipes are being encountered more and more often in industrial situations. This thesis studies the effect of 180o bends on the characteristics and development of gas-liquid two-phase flows in large diameter downward and upward pipes. The study particularly focuses on the influence of serpentine configuration on flow structure, cross-sectional void distribution and circumferential liquid film profiles and their development along the downward and upward sections. It was found that both the top and bottom bends have considerable impacts on flow behaviour, although to varying degrees. These impacts were highly dependent on the air and water flow rates. For sufficient flow rates, the bends were observed to create flow maldistribution in the adjacent straight section, due to the effects of centrifugal force. The air moved towards the inner zone of the bend and the water towards the outer zone, while a lesser quantity of water was identified on the other surfaces of the pipe. Investigation of the film thickness development in the downward and upward sections showed that, the liquid film behaviour close to the bends was significantly different from those located further away. This can be attributed to the centrifugal force of the bends. Examination of the power spectral density (PSD) along the downward and upward sections showed that, the shape of PSD located in the adjacent section to the bends, was substantially different from those located further away. Furthermore, several flow regime maps were generated which showed that, in addition to bubbly, intermittent and annular flows, unstable flows existed along the upward section, particularly for low gas and water flow rates. In this study it was found that, the lower bend was periodically blocked by the liquid and then blown through by the accumulated air. The data obtained from this study were compared with different theoretical correlations found in the existing literature. Some discrepancy between the results of the current study and those of previous published materials was noted. Updated correlations were presented which provided well results when they applied for the data obtained from the current study and previous studies.