Additive manufacturing (AM) is a rapidly growing and evolving form of product development that has the potential to revolutionize both the industrial and academic spheres. For example, AM offers much greater freedom of design while producing significantly less waste than most traditional manufacturing techniques such as injection and blow molding. Filament-based material extrusion AM, commonly referred to as fused filament fabrication (FFF), is one of the most well-known AM modalities using a polymeric feedstock; however, several obstacles currently prohibit widespread use of this manufacturing technique to produce end-use products, which will be discussed in this dissertation. Specifically, a severely limited material catalog restricts tailored product development and the variety of applications. Additionally, poor interlayer adhesion results in anisotropic mechanical properties which can lead to failure, an issue not often observed in traditional manufacturing techniques. A review of the current state of the art research in the field of FFF, focusing on the multiphysics-based modeling of the system and exploring some empirically determined relationships, is presented herein to provide a more thorough understanding of FFF and its complexities. This review further guides the work discussed in this dissertation. The primary focus of this dissertation is to expand the fundamental understanding of the FFF process, which has proven difficult to measure directly. On this size scale, introduction of measurement devices such as thermocouples and pressure transducers can significantly alter the behavior of the process or require major changes to the geometry of the system, leading to spurious measurements, incorrect outcomes, and/or conclusions. Therefore, the research presented in this dissertation focuses on the development and validation of predictive models based on first principles approaches that can provide information leading to the optimization of printing parameters and exploration of novel and/or modified materials without an exhaustive and inefficient trial-and-error process. The first potential issue a novel material may experience in FFF is an inability to extrude from the heated nozzle. Prior to this work, no efforts were focused on the molten material inside the liquefier and its propensity to flow in the reverse direction through the annular region between the filament and the nozzle wall, referred to as annular backflow. The study presented in this dissertation explores this phenomenon, determining its cause and sensitivity to processing parameters and material properties. A dimensionless number, named the "Flow Identification Number" or FIN, is defined that can predict the propensity to backflow based on the material's shear thinning behavior, the filament diameter, the nozzle diameter, and the filament feed rate and subsequent pressure inside the nozzle. An analysis of the FIN suggested that the backflow potential of a given material is most sensitive to the filament diameter and its shear thinning behavior (power law index). The predictive model and FIN were explored using three materials with significantly different onsets of shear thinning. The experiments validated both the backflow model and a previously derived buckling model, leading to the development of a rapid screening technique to efficiently estimate the extrudability of a material in FFF. Following extrusion from the nozzle, the temperature profile of the deposited filament will determine nearly all of the mechanical properties of the printed part as well as the geometry of the individual roads and layers because of its temperature dependent viscoelastic behavior. Therefore, to better understand the influence of the temperature profile on the evolution of the road geometry and subsequent interlayer bonding, a three-dimensional finite element heat transfer analysis was developed. The focus of this study is the high use temperature engineering thermoplastic polymer polyetherimide, specifically Ultem™ 1010, which had not been studied in prior modeling analyses but presents significant challenges in terms of large thermal gradients and challenging AM machine requirements. Through this analysis, it was discovered that convective cooling dominated the heat transfer (on the desktop FFF scale) producing a significant cross-sectional temperature gradient, whereas the gradient along the axis was observed to be significantly smaller. However, these results highlighted a primary limitation in computer modeling based on computational time requirements. This study, utilizing a well-defined three-dimensional model based on a geometry measured empirically, produced results describing 0.5 s of printing time in the printing process and elucidated great details in the road shape and thermal profile, but required more than a week of computation time, suggesting a need for to modify the modeling approach while still accurately capturing the physics of the FFF layer deposition process. The determination of the extensive time required to converge the three-dimensional model, as well as the identification of a relative lack of axial thermal transfer, led to the development of a two-dimensional, cross-sectional heat transfer analysis based on a finite difference approach. This analysis was coupled with a diffusion model and a stress development model to estimate the recovery of the bulk strength and warping potential of a printed part, respectively. Through this analysis, it was determined that a deposited road may remain above Tg for 2-10 s, depending on the layer time, or time required for the nozzle to pass a specific point in the x-y plane between each layer. The predicted strength recovery was significantly overestimated, leading to the discovery of the extreme sensitivity of the predictive models to the relaxation time of a material, particularly at long layer times. When the deposited filament has enough time to attain an equilibrium temperature, small changes in the relaxation time of the material resulted in significant changes in the predicted healing results. These results highlight the need for exact estimations of the material parameters to accurately predict the properties of the final print. / Doctor of Philosophy / Additive manufacturing (AM), particularly filament-based material extrusion additive manufacturing, commonly known as fused filament fabrication (FFF), has recently become the subject of much study with the goal of utilizing it to produce parts tailored to specific purposes quickly and cheaply. AM is especially suited to this purpose due to its ability to produce highly complex parts with the ability to change design very easily. Furthermore, AM typically produces less waste than many traditional manufacturing techniques due to the process building a part layer by layer rather than removing unneeded material from a larger piece, resulting in a cheaper process. These freedoms make AM, and FFF in particular, highly prized among industrial producers. However, numerous challenges prevent the adoption of FFF by these companies. Particularly, a lack of available material options and anisotropic material properties lead to issues when attempting to produce a part targeted for use in a specific field. FFF is primarily commercially limited to two materials: polylactic acid (PLA) and acrylonitrile-butadiene-styrene (ABS) with a few other materials available in more specialized fields. However, essentially all these materials are limited to low use temperatures (less than 300 °C) and are primarily amorphous or with nearly negligible amounts of crystallinity. This severely limits the ability to tailor a printed part to a specific purpose and restricts the use of printed parts to applications requiring very low strengths. This is one reason why FFF, and most types of AM, is limited to the prototyping field rather than end-use applications. The other reason, anisotropic mechanical properties, is caused by the building methodology of AM. Creating a part layer by layer naturally introduces potential areas of weakness at the joining of the layers. If bulk properties are not recovered, the interlayer bond acts as a stress concentrator under load and will break before the bulk material. The work presented in this dissertation proposes methods to better understand the FFF system in order to address these two issues, leading to the optimization of the printing process and ability to expand the material catalog, particularly in the direction of high use temperature materials. The research discussed herein attempts to develop predictive models that may allow exploration into the FFF system which can be difficult to do experimentally, and by predicting the properties of a printed part, the models can guide future experimentation in FFF without the need for an extensive trial-and-error process. The work presented in this dissertation includes exploring the flow phenomena inside the FFF nozzle to determine extrudability as well as two-dimension and three-dimension heat transfer models with the goal of describing the viscoelastic, flow, diffusion, and stress development phenomena present in FFF.

In a gas turbine, a small portion of air is bled from the compressor to provide cooling to keep the turbine at a safe operating temperature. The air flows through several passages in between where the components of the turbine are assembled. In this study, the heat transfer and pressure loss characteristics of two of these passages are investigated experimentally. The first of the two passages investigated is the passage in between the turbine blade root and disc. This passage has a unique geometry resembling an S-shape. The heat transfer and pressure loss characteristic of this passages in not well documented. For this study, a model of the realistic S-shaped passage has been made. In addition, a simplified rectangular duct with hydraulic diameter similar to that of the realistic S-shaped passage was constructed along with three other rectangular passages at aspect ratios, 17.33, 8.81, 3.93, and 2.02. This study aims to determine if rectangular duct correlations are valid for the realistic S-shaped model. Specifically, flow in low Reynolds number ranges of less than 3000 are of interest. With the effect or rotation and aspect ratio being of primary concern in the study, an experimental rig was constructed to measure the heat transfer and pressure loss in these models. The experiments were conducted with both clockwise and counterclockwise rotation to account for the passage on the pressure side and suction side of the passage. The centerline Nusselt number distribution measured to check if the flow was fully developed. The effect of rotation caused swirling, increasing the entrance length in the duct and also enhanced heat transfer. The rotation also enhanced the heat transfer in the fully developed region. The fully developed experimental data for the simplified rectangular ducts showed good correlation with that of literature. However, the realistic S-shaped duct showed lower heat transfer values than the simplified rectangular ducts. Still, the effect of rotation is seen enhancing the rotation inf the realistic S-shaped duct. Additionally, the friction factor which was measured using the cross-sectional average static pressure showed similar results for the realistic S-shaped duct and the simplified rectangular duct. The passage between turbine disc bore and shaft is modeled as an annular duct with inner surface rotation. Flow in the turbulent region is studied and the test sections are made to have short length to hydraulic dimeter ratios. Along the centerline, the onset of Taylor vortices can be seen enhancing the Nusselt number in regions where the flow should be fully developed. This effect can also be seen enhancing the heat transfer in the fully developed region. The presence of Taylor vortices also adds resistance increasing the pressure loss across the duct. / Master of Science / Industrial gas turbines are designed to have an optimum overall pressure ratio for target temperatures rise. The demand for higher efficiency and power continues to push the operating pressure and temperature. Air systems is the flow network to provide necessary cooling to keep the machinery at a safe operating temperature. In this study, two passages of the air system in the turbine are of interest. The passage between turbine blade root and disc, and the passage between the turbine disc and shaft. The effect of rotation on the flow through the two passages are of primary interest with focus on heat transfer and pressure loss characteristics. This experimental study presents unique results as a realistic model of the passage which resembles an S-shape was constructed and tested. The passage in between the turbine disc and shaft forms a rotating annular passage. There is limited data available representing the realistic geometrical shape of the annular passage under rotation. Therefore, the present study aims to present data for more realistic geometry and operating conditions. In addition, simplified rectangular ducts and annular ducts are also tested for comparison purpose. The results of the study showed that the rotation does provide a significant increase in heat transfer and pressure loss in experiment modeling the passage between the turbine blade root and disc. Comparing the realistic S-shape passage and the rectangular passage with similar aspect ratio, the realistic S-shape passage showed less heat transfer and less sensitivity to the effect of rotation. The pressure loss characteristics on the other hand proved to be very similar. For the experiments modeling the passage between turbine disc and shaft, the effect of rotation once again showed to increase the heat transfer and pressure loss. The effect is more prominent when there is less axial flow.

RANS models in CFD are used to predict the liner wall heat transfer characteristics of a gas turbine annular combustor with radial swirlers, over a Reynolds number range from 50,000 to 840,000. A three dimensional hybrid mesh of around twenty five million cells is created for a periodic section of an annular combustor with a single radial swirler. Different turbulence models are tested and it is found that the RNG k-e model with swirl correction gives the best comparisons with experiments. The Swirl number is shown to be an important factor in the behavior of the resulting flow field. The swirl flow entering the combustor expands and impinges on the combustor walls, resulting in a peak in heat transfer coefficient. The peak Nusselt number is found to be quite insensitive to the Reynolds number only increasing from 1850 at Re=50,000 to 2200 at Re=840,000, indicating a strong dependence on the Swirl number which remains constant at 0.8 on entry to the combustor. Thus the peak augmentation ratio calculated with respect to a turbulent pipe flow decreases with Reynolds number. As the Reynolds number increases from 50,000 to 840,000, not only does the peak augmentation ratio decrease but it also diffuses out, such that at Re=840,000, the augmentation profiles at the combustor walls are quite uniform once the swirl flow impinges on the walls. It is surmised with some evidence that as the Reynolds number increases, a high tangential velocity persists in the vicinity of the combustor walls downstream of impingement, maintaining a near constant value of the heat transfer coefficient. The computed and experimental heat transfer augmentation ratios at low Reynolds numbers are within 30-40% of each other. / Master of Science

Rotordynamic instability problems in turbomachinery have become more important in recent years due to rotordynamic components with higher speeds and higher power densities. These features typically lead to increased instability risk in rotor dynamic components as fluids-structure interactions take place. In addition, critical damage of rotordynamic components can result from high level vibrations of supporting bearing system, where the reduced rotor speed can lead to system operating near the rotor critical speed. Therefore, increased accuracy in modeling of rotordynamic components is required to predict the potential instability issues in high performance rotordynamic design. The instability issue may potentially be eliminated in design stage by varying the characteristics of the unstable components. One such turbomachinery component is the annular pressure seal. The annular pressure seals are specifically designed to prevent the fluid leakage from high pressure stage to low pressure stage in turbomachinery. Typical annular pressure seals have two different flow regions, an annular jet-flow region between the rotor and stator, and cylindrical or circumferential indentions on the stator/rotor surface that serve as cavities where flow recirculation occurs. As the working fluid enters the cavities and recirculates, the kinetic energy is reduced, resulting in a reduction of leakage flow. The current challenge is to model with higher precision the interaction between the rotordynamic components and the working fluid. In this dissertation, this challenge was overcome by developing a hybrid Bulk Flow/CFD method to compute rotordynamic responses for the annular pressure seals. In addition, design of experiments studies were performed to relate the surface patterning with the resulting rotordynamic response for the annular pressure seals, in which several different geometry specifications were investigated. This study on annular pressure seal design generated regression models for rotordynamic coefficients that can be used as optimization guidelines. Research topics related to the annular pressure seals were presented in this dissertation as well. The reduced order model of both hole-pattern seals and labyrinth seals were investigated. The results showed that the flow field representing the flow dynamics in annular pressure seals can be expressed as a combination of first three proper orthogonal decomposition modes. In addition, supercritical state of carbon dioxide (sCO2) process fluid was examined as the working fluid in a preliminary study to better understand the effects on annular pressure seals. The results showed that the performance and stability in the annular pressure seals using sCO2 as process fluid can both be improved. / Doctor of Philosophy / This dissertation focused on understanding the correlations between surface patterning and rotordynamic responses in the annular pressure seals. The annular pressure seals are a specific type of rotordynamic component that was designed to prevent the fluid leakage from high pressure stage to low pressure stage in turbomachinery. As the working fluid enters the cavities and recirculates, the kinetic energy is reduced, resulting in a reduction of leakage flow through the annular pressure seals. Rotordynamic instability becomes an issue that may be related to the annular pressure seals in some cases. In recent years, rotordynamic components with higher rotor speeds and higher power densities are commonly used in industrial applications. These features could lead to increased instability risk in rotor-bearing systems as fluids-structure interactions take place. Therefore, high precision modeling of the rotodynamic components is required to predict the instability issues in high performance rotordynamic design. The instability issue may potentially be eliminated in design stage by varying the characteristics of the potentially unstable components. In this study, the surface patterning and rotordynamic responses were investigated for several different annular pressure seal models with a hybrid Bulk Flow/Computational Fluid Dynamics method. This dissertation provides for the first time regression models for rotordynamic coefficients that can be used as optimization guidelines. Research topics related to the annular pressure seals were presented in this dissertation as well. The reduced order model of both hole-pattern seals and labyrinth seals were investigated. The results showed that the flow field representing the flow dynamics in annular pressure seals can be expressed as a combination of first three proper orthogonal decomposition modes. In addition, supercritical state of carbon dioxide (sCO2) process fluid was examined to better understand the effects of working fluid on annular pressure seals. The results showed that the performance and stability in the annular pressure seals using sCO2 as process fluid can both be improved.

In 1998, the Rome Statute established the International Criminal Court (ICC) to end impunity for violators of international human rights law. As the ICC is opening criminal investigations for the first time in its existence, it is important to determine the legitimacy of the young institution in order to understand its importance in international politics and international legal precedence. These first cases can be used to illustrate that while some fears might be misplaced, others are sadly realized. Especially through the criminal investigation processes in Darfur, the ICC has acted responsibly and has not violated its founding principles or Sudan's sovereignty. Conversely, ICC intervention in Uganda has created a political situation that pits the prospect of peace against the pursuit of justice. If the ICC is able to prove that it is responsible in its judicial processes, it will likely become a legitimized institution. An increased role by the international community in ICC affairs would also bring a level of comfort and transparency that has not yet been realized. Furthermore, as individual states begin to use diplomatic means to enforce the norms of international human rights, the court might be used infrequently, and only when it is critical in the pursuit of justice. Despite the difficulties. faced by the ICC, it has the potential to gain legitimacy and become a recognizable player on the international political scene.

The mean strengths of the wintertime stratospheric polar vortices are known to be related to the phase of the quasi-biennial oscillation (QBO) in the tropical stratosphere from circulation statistics - the "Holton-Tan relationship". The principal topic of this thesis is improving understanding of the mechanism behind the QBO's influence. Following the example of previous studies, the QBO influence on the Northern Hemisphere (NH) extratropics on monthly time scales in an observational reanalysis is examined, and is shown to closely resemble the stratospheric Northern annular mode (NAM). It is argued that this may not be informative about the mechanism, as the response could be NAM-like for many different mechanisms. It is suggested that examining the transient response of the NH extratropics to forcing by the QBO would be much more informative, particularly on time scales of a few days. In a primitive equation model of the middle atmosphere, the long-term stratospheric NH response to imposed zonal torques is often found to be NAM-like under perpetual January conditions, with wave feedbacks making a very important contribution. However, the response in runs with a seasonal cycle is not NAM-like. Investigation of the transient responses indicates the wave feedbacks are qualitatively similar in each case but only strong enough under perpetual January conditions to make the long-term response NAM-like. This supports the hypothesis that feedbacks from large-scale dynamics tend to make the stratospheric response to arbitrary forcings NAM-like, and therefore indicates that the long-term response is not generally useful for understanding forcing mechanisms. Examining the short-term transient response to known torques is found to be more successful at inferring information about the torques than several other previously proposed methods. Finally, the short-term transient response of the NH extratropics to forcing by the easterly QBO phase in a general circulation model is found to be consistent with the proposed mechanism of Holton and Tan (1980), indicating that this mechanism plays a role in the Holton-Tan relationship.

Multiphase flows are of great interest to a large variety of industries because flows of two or more immiscible liquids are encountered in a diverse range of processes and equipment. However, the advent of high viscosity oil requires more investigations to enhance good design of transportation system and forestall its inherent production difficulties. Experimental and numerical studies were conducted on water-sand, oil-water and oilwater- sand respectively in 1-in ID 5m long horizontal pipe. The densities of CYL680 and CYL1000 oils employed are 917 and 916.2kg/m3 while their viscosities are 1.830 and 3.149Pa.s @ 25oC respectively. The solid-phase concentration ranged from 2.15e-04 to 10%v/v with mean diameter of 150micron and material density of 2650kg/m3. Experimentally, the observed flow patterns are Water Assist Annular (WA-ANN), Dispersed Oil in Water (DOW/OF), Oil Plug in Water (OPW/OF) with oil film on the wall and Water Plug in Oil (WPO). These configurations were obtained through visualisation, trend and the probability density function (PDF) of pressure signals along with the statistical moments. Injection of water to assist high viscosity oil transport reduced the pressure gradient by an order of magnitude. No significant differences were found between the gradients of oil-water and oil-water-sand, however, increase in sand concentration led to increase in the pressure losses in oil-water-sand flow. Numerically, Water Assist Annular (WA-ANN), Dispersed Oil in Water (DOW/OF), Oil Plug in Water (OPW/OF) with oil film on the wall, and Water Plug in Oil (WPO) flow pattern were successfully obtained by imposing a concentric inlet condition at the inlet of the horizontal pipe coupled with a newly developed turbulent kinetic energy budget equation coded as user defined function which was hooked up to the turbulence models. These modifications aided satisfactory predictions.

Uma das dificuldades relacionadas com a exploração de petróleo é o transporte de óleo pesado, que devido a sua alta viscosidade, acarreta em uma elevada perda de carga no sistema. Para proporcionar economia de energia aplica-se o método do Core Annular Flow (CAF) onde é utilizado um escoamento anular bifásico em que a água escoa na periferia da tubulação para redução do gasto energético. O presente trabalho visou compreender e reproduzir este fenômeno, desenvolvendo simulações em CFD através do pacote comercial ANSYS FLUENT considerando o escoamento 3D, turbulento, isotérmico e incompressível para casos estacionários e transientes. A interface entre a água e o óleo foi adequadamente reproduzida em diferentes geometrias como tubo reto e com curva. O método LES para simulação de grandes escalas provou ser o melhor método de turbulência dentre os testados, como k-epsilon e modelo de tensores de Reynolds, de forma com que a interface fosse representada corretamente. O modelo para sistema multifásico adotado foi o Volume de Fluido (VOF), comparado com o comportamento experimental e com dados da literatura. Os fenômenos de swirl observados experimentalmente também foram reproduzidos de forma satisfatória. / One of the difficulties related to oil exploration is the transportation of heavy oil, which due to its high viscosity, causes a high pressure drop in the system. In order to provide energy savings, the Core Annular Flow (CAF) method applies where a two-phase annular flow occurs in which water flows at the periphery adjacent to the pipe to reduce energy expenditure. The present work aimed to understand and reproduce this phenomenon, developing CFD simulations through the commercial package ANSYS FLUENT considering flow as 3D, turbulent, isothermal and incompressible for stationary and transient cases. The interface between water and oil has been properly reproduced in different geometries such as straight pipe and pipe with a curve. The LES method for large scale simulation proved to be the best turbulence method among the tested, such as k-epsilon and Reynolds stress model, so that the interface was correctly represented. The model for the multiphase system adopted was the Volume of Fluid (VOF), compared to the experimental behavior and with data from the literature. The experimentally observed swirl phenomena were also reproduced satisfactorily.

Escoamentos gás-líquido assim como escoamento líquido-líquido-gás em duto de geometria anular estão presentes em muitas aplicações industriais, por exemplo, em poços de petróleo direcionais. No entanto, até mesmo características globais de escoamento gás-líquido nessa geometria, como os padrões de escoamento ou gradiente de pressão, não são ainda totalmente compreendidas. E ainda, informações são escassas quando se refere a escoamento trifásico nessa geometria, cuja aplicação está relacionada ao fenômeno de inversão de fase, que é de extrema importância não apenas para ao setor petrolífero, como para a indústria alimentícia. O presente estudo experimental tem como objetivo avaliar o escoamento líquido-gás, apresentar dados inéditos de escoamento gás-líquido para três viscosidades de óleo, além de avaliar o fenômeno de inversão de fase em escoamento ascendente vertical em duto anular de grande diâmetro. Um aparato experimental inclinável com 10,5 m de comprimento foi projetado e construído para este trabalho. As dimensões radiais do duto anular estão em escala real, conforme se verifica em poços de petróleo e gás. A investigação em escoamento gás-líquido foi conduzida utilizando água, óleo e ar comprimido como fluidos de trabalho em escoamento ascendente vertical em duas geometrias: (i) um tubo com diâmetro de 95 mm e (ii) um duto de configuração anular e concêntrico, com diâmetro hidráulico de valor igual ao diâmetro do tubo. A avaliação do fenômeno de inversão de fase em escoamento trifásico foi conduzida em condições equivalentes em três geometrias: (i) tubo vertical menor com diâmetro de 50 mm, (ii) tubo com diâmetro de 95 mm e (iii) um duto anular concêntrico. Padrões de escoamento, queda de pressão e fração volumétrica de fase foram obtidos para ambos os escoamentos gás-líquido e líquido-líquido-gás. Os dados coletados nesse trabalho são de grande importância para o desenvolvimento de novas correlações de fechamento, que são essenciais para o projeto otimizado de poços de petróleo. Dados inéditos de escoamento bifásico óleo-gás são apresentados, bem como um estudo pioneiro em inversão de fase em escoamento trifásico com velocidade superficial de gás e viscosidade do óleo elevadas. / Two-phase flows as well as three-phase flow in annular geometry are present in many industrial applications, for example in oil directional wells. However, even global characteristics of gas-liquid flow in this geometry, such as flow patterns and pressure gradient are not fully understood. Moreover, information is scarce when it refers to three-phase flow in this geometry, which application is related to the phase inversion phenomenon, which is of extreme importance and not only for the oil industry. This experimental study aims to evaluate the liquid-gas flow, present new data from gas-liquid flow for three oil viscosities and evaluate the phase inversion phenomenon in vertical upward flow in large diameter annular duct. An experimental apparatus with 10.5 m length was designed and built for this work. The radial dimensions of the annular duct are similar to full scale, as observed in oil and gas wells. The investigation into gas-liquid flow was conducted using water, oil and compressed air as working fluids in an ascending vertical flow in two geometries: (i) a tube with 95 mm diameter and (ii) a concentric annular duct with hydraulic diameter equivalent to the tube internal diameter. The evaluation of the phase inversion phenomenon in three-phase flow was conducted under equivalent conditions for three geometries: (i) smaller vertical tube with 50 mm of internal diameter, (ii) tube with 95 mm of internal diameter and (iii) concentric annular duct with hydraulic diameter of 95 mm. Flow patterns, pressure drop and volumetric phase fraction were obtained for both gas-liquid and gas-liquid-liquid flows. The data collected in this study are of great importance for the development of new closing correlations, which are essential for the optimized design of oil wells. New two-phase flow data for three oil viscosities, not found in the literature, are presented as well as a pioneer study in three-phase-flow phase inversion with high oil viscosity and high superficial gas velocity.

Uma das dificuldades relacionadas com a exploração de petróleo é o transporte de óleo pesado, que devido a sua alta viscosidade, acarreta em uma elevada perda de carga no sistema. Para proporcionar economia de energia aplica-se o método do Core Annular Flow (CAF) onde é utilizado um escoamento anular bifásico em que a água escoa na periferia da tubulação para redução do gasto energético. O presente trabalho visou compreender e reproduzir este fenômeno, desenvolvendo simulações em CFD através do pacote comercial ANSYS FLUENT considerando o escoamento 3D, turbulento, isotérmico e incompressível para casos estacionários e transientes. A interface entre a água e o óleo foi adequadamente reproduzida em diferentes geometrias como tubo reto e com curva. O método LES para simulação de grandes escalas provou ser o melhor método de turbulência dentre os testados, como k-epsilon e modelo de tensores de Reynolds, de forma com que a interface fosse representada corretamente. O modelo para sistema multifásico adotado foi o Volume de Fluido (VOF), comparado com o comportamento experimental e com dados da literatura. Os fenômenos de swirl observados experimentalmente também foram reproduzidos de forma satisfatória. / One of the difficulties related to oil exploration is the transportation of heavy oil, which due to its high viscosity, causes a high pressure drop in the system. In order to provide energy savings, the Core Annular Flow (CAF) method applies where a two-phase annular flow occurs in which water flows at the periphery adjacent to the pipe to reduce energy expenditure. The present work aimed to understand and reproduce this phenomenon, developing CFD simulations through the commercial package ANSYS FLUENT considering flow as 3D, turbulent, isothermal and incompressible for stationary and transient cases. The interface between water and oil has been properly reproduced in different geometries such as straight pipe and pipe with a curve. The LES method for large scale simulation proved to be the best turbulence method among the tested, such as k-epsilon and Reynolds stress model, so that the interface was correctly represented. The model for the multiphase system adopted was the Volume of Fluid (VOF), compared to the experimental behavior and with data from the literature. The experimentally observed swirl phenomena were also reproduced satisfactorily.