Wall-bounded turbulent flows such as plane Couette flow, channel, pipe flows and boundary layer flows are fundamental problem of interest that we often meet in many scientific and engineering situations. The goal of the present thesis is to investigate the origin of large-scale streaky motions observed in the wall-bounded turbulent flows. Under a hypothesis that the large-scale streaky motions sustain with a process similar to the well-known near-wall self-sustaining cycle, the present thesis have pursued on four separate subjects: (i) non-modal amplification of streaks, (ii) the secondary instability of the finite amplitude streaks, (iii) existence of a self-sustaining process at large scale and (iv) turbulent skin friction reduction by forcing streaks. First, using a linear model with turbulent mean flow and the related eddy viscosity, it is shown that the streaks are largely amplified by harmonic and stochastic forcing. The largely amplified streaks undergo the secondary instability and it has been associated with the formation of the large-scale motions (bulge). The existence of a self-sustaining process involving the amplification and instability of streaks at large scale is proved by quenching the smaller-scale energy carrying eddies in the near-wall and logarithmic regions. Finally, it is shown that artificially forcing of large-scale streaks reduce the turbulent skin friction up to 10\% by attenuating the near-wall streamwise vortices.

Advances in numerical optimization have raised the possibility that efficient and novel aircraft configurations may be ``discovered'' by an algorithm. To begin exploring this possibility, a fast and robust set of tools for aerodynamic shape optimization is developed. Parameterization and mesh-movement are integrated to accommodate large changes in the geometry. This integrated approach uses a coarse B-spline control grid to represent the geometry and move the computational mesh; consequently, the mesh-movement algorithm is two to three orders faster than a node-based linear elasticity approach, without compromising mesh quality. Aerodynamic analysis is performed using a flow solver for the Euler equations. The governing equations are discretized using summation-by-parts finite-difference operators and simultaneous approximation terms, which permit nonsmooth mesh continuity at block interfaces. The discretization results in a set of nonlinear algebraic equations, which are solved using an efficient parallel Newton-Krylov-Schur strategy. A gradient-based optimization algorithm is adopted. The gradient is evaluated using adjoint variables for the flow and mesh equations in a sequential approach. The flow adjoint equations are solved using a novel variant of the Krylov solver GCROT. This variant of GCROT is flexible to take advantage of non-stationary preconditioners and is shown to outperform restarted flexible GMRES. The aerodynamic optimizer is applied to several studies of induced-drag minimization. An elliptical lift distribution is recovered by varying spanwise twist, thereby validating the algorithm. Planform optimization based on the Euler equations produces a nonelliptical lift distribution, in contrast with the predictions of lifting-line theory. A study of spanwise vertical shape optimization confirms that a winglet-up configuration is more efficient than a winglet-down configuration. A split-tip geometry is used to explore nonlinear wake-wing interactions: the optimized split-tip demonstrates a significant reduction in induced drag relative to a single-tip wing. Finally, the optimal spanwise loading for a box-wing configuration is investigated.

Bakgrund: Vårdmiljön inom psykiatrisk heldygnsvård har beskrivits framkalla olika känslor och präglas av en hård miljö där patienter bland annat kan vårdas mot sin vilja och vara utsatta för tvångsåtgärder och restriktioner. Aggressivitet är vanligt förekommande på dessa avdelningar och bedöms vara ett problem. En kunskapslucka finns vad gäller vilka patienter och situationer som ökar risken för aggressivitet inom kontexten psykiatrisk heldygnsvård. Syfte: Att identifiera karaktäristiska drag hos patienter med aggressivt beteende och identifiera aspekter som påverkar situationer där hot- och våldsincidenter uppstått inom psykiatrisk heldygnsvård samt syntetisera en förklaringsmodell. Metod: En integrativ litteraturöversikt beståendes av både kvalitativa och kvantitativa artiklar. Materialet analyserades med hjälp av Whittemore och Knafls (2005) arbetsprocess. Resultat: Resultatet genererade i tre huvudteman och tio underteman. Följande tre huvudteman identifierades: patienten som en trigger, vårdmiljön som en trigger och personalen som en trigger. Diskussion: Metoden diskuteras utifrån begreppen: trovärdighet, pålitlighet, bekräftelsebarhet och överförbarhet. Resultatets huvudfynd diskuteras med stöd av tidigare forskning och i relation till Phil Barkers teori tidvattenmodellen. / Background: The care environment within psychiatric inpatient care has been described to create different emotions and is characterized as a hard environment where patients sometimes are treated against their will and can be exposed to coercive measures and restrictions. Aggressiveness is common at these wards and is considered a problem. There is a knowledge gap when it comes to patients and situations that increase the risk for aggressiveness in the context of psychiatric inpatient care. Aim: To identify characteristic features of aggressive patients and to identify aspects that effects situations where threats and violence has occurred in psychiatric inpatient care and to synthesise an explanatory model. Method: An integrative literature overview containing both qualitative and quantitative articles. The data were analysed using Whittemore and Knafl’s (2005) working procedure. Results: The result generated in three main themes and ten subthemes. Following three main themes were identified: the patient as a trigger, the care environment as a trigger and the staff as a trigger. Discussion: The method is discussed in relation to these concepts: trustworthiness, dependability, confirmability and transferability. The results are discussed with support of previous research and in relation to Phil Barker's theory the Tidal model.

Approved for public release, distribution is unlimited / For over half a century the NPS Aerolabʼ Low Speed Wind Tunnel located in Halligan Hall of the Naval Postgraduate school has served to provide students and faculty with meaningful aerodynamic data for research and problem analysis. New data acquisition hardware was installed three years ago but never fully verified, and contained no integrated software program to collect data from the strain-gauge balance pedestal. Existing National Instruments based hardware for the NPS low-speed wind tunnel was reconfigured to obtain data from the strain-gauge pedestal. Additionally, a data acquisition software program was written in LabVIEW⠭ to accommodate the hardware. The Virtual Instruments (VI) program collects and plots accurate data from all four strain gauges in real-time, producing non-dimensional force and moment coefficients. A research study on the performance of an OH-6A helicopter fuselage was conducted. NPS Aerolabʼ wind tunnel tests consisted of drag, lift, and pitching moment measurements of the OH-6A along yaw and angle-of-attack sweeps. The results of the NPS wind tunnel data were compared against testing conducted on a full-scale OH-6A helicopter in NASA Ames' 40 ft. x 80ft. wind tunnel, along with the U.S. Army's Light Observation Helicopter (LOH) wind tunnel tests. Results of current testing substantiate the LabVIEW⠭ code. / Ensign, United States Navy

International aviation regulations on emissions are becoming more strict. Improvements goals on fuel efficiency demand development of technologies capable of reducing fuel consumption and gas emissions. Morphing structures capability to adapt their aerodynamic shape for optimal condition in flight brings potential for reduction of aircraft drag and operating fuel consumption, minimizing gas emissions and fuel expenses. This study presents an investigation on the impact of a camber morphing winglet on midsize business jet using numerical simulation and wind tunnel experiments. A genetic algorithm was used to optimize the winglet sections camber for different flight conditions. Optimized geometries achieved total drag reduction of up to 0.58% compared to original winglet for single condition optimization, reaching up to 7 % reduction on consumed fuel on a typical mission. This efficiency improvement allows aircraft to carry 900 kg additional load, comprising the morphing system and extra payload. There is an indication of even better results for applications on a bigger commercial jet. Presented methodology is also suitable for new winglet fixed geometry design or incorporating morphing technology. Aerodynamic balance force measurements showed that optimized winglets increased the wing effective aspect ratio (AReff), reducing the lift-induced drag, and maximum lift coefficient (CLmax). However, maximum lift to drag ratio (L/Dmax) was reduced on CL optimization region due to flow differences between optimization and wind tunnel conditions. Aerodynamic efficiency improvement was found for greater lift coefficients (CL). Reductions on wing tip vortex size and intensity due to winglet installation are seen on measured vorticity map, showing liftinduced drag reduction according to Maskells equation. Parabolic drag polar and Maskells equation methods were used for lift-induced drag calculation, using balance force and flowing mapping data for calculations. The presented concept showed considerable aircraft performance improvement, using a feasible device with greater certification ease than other morphing structures concepts, once the failure of this system would not compromise flight safety. Further investigation using computational fluid dynamics (CFD) and wind tunnel experiments is necessary to develop and test a functional camber morphing winglet device. / Regulamentações internacionais sobre emissões estão se tornando mais rigorosas. Metas de melhoria da eficiência de consumo de combustível demandam o desenvolvimento de tecnologias capazes de reduzir o consumo e emissões de gases. Estruturas capazes de adaptar sua forma aerodinâmica para condição ótima em voo trazem potencial de redução do arrasto e consumo de combustível da aeronave, minimizando as emissões de gases e gastos com combustível. Este estudo apresenta uma investigação sobre o impacto de uma winglet de camber variável em um jato executivo da categoria mid size utilizando simulação numérica e experimentos em túnel de vento. Um algoritmo genético foi usado para otimizar o camber das seções para diferentes fases de voo. As geometrias otimizadas reduziram o arrasto total em até 0.58% comparadas a winglet original na otimização de condição única, alcançando até 7% de redução no combustível consumido em missão típica. Essa melhoria de eficiência permite a aeronave carregar 900 kg de carga adicional, composta pelo sistema de adaptação e carga paga extra. Há uma indicação de resultados ainda melhores para aplicação em um jato comercial maior. A metodologia apresentada é apropriada para projeto de uma nova winglet de geometria fixa ou que incorpore a tecnologia de adaptação. Medidas de força com balança aerodinâmica mostraram que as winglets otimizadas aumentaram o alongamento efetivo da asa (AReff), reduzindo o arrasto induzido, e o coeficiente de sustentação máximo (CLmax). No entanto, a máxima razão entre sustentação e arrasto (L/Dmax) foi reduzida dentro do intervalo de CL da otimização devido as diferenças entre as condições do escoamento na otimização e no túnel de vento. Melhoria na eficiência aerodinâmica foi obtida para coeficientes de sustentação (CL) maiores. Reduções no tamanho e intensidade do vórtice de ponta de asa são vistas nos mapas de vorticidade medidos, mostrando redução do arrasto induzido segundo a equação de Maskell. Os métodos da polar de arrasto parabólica e da equação de Maskell foram usados para o cálculo do arrasto induzido, utilizando nos cálculos os dados de força da balança e o mapeamento do escoamento. O conceito apresentado mostrou melhoria considerável no desempenho da aeronave, utilizando um sistema factível e com maior facilidade para certificação que outros conceitos de estruturas adaptáveis, uma vez que a falha desse sistema não comprometeria a segurança do voo. Mais estudos são necessários para desenvolver e testar uma winglet de camber varável funcional.

Cette thèse CIFRE est le fruit d’une collaboration entre Renault Trucks et le LMFA dans la perspective d’une évaluation de la pertinence du contrôle actif pour la réduction de traînée de véhicule industriel. Les deux principaux objectifs de ces travaux expérimentaux consistent à l’analyse de l’influence de l’écoulement de soubassement sur la dynamique du sillage et l’étude d’une stratégie de contrôle d’écoulement combinant des volets déflecteurs (positionnés sur les bords supérieurs et latéraux du culot) à des actionneurs de type jets pulsés dans l’optique d’une réduction de la traînée aérodynamique d’un corps non profilé à culot droit. Le développement du sillage pour différentes vitesses de soubassement évoluant de 10% à plus de 80% de la vitesse de l’écoulement infini amont est étudié sur une maquette simplifiée de véhicule poids lourd à l’échelle 1/43e. Des mesures de pression au culot permettent d’identifier quatre classes d’écoulement associées à des structures de sillage différentes mises en évidence par des mesures PIV 2D-3C. Le sillage de la première classe d’écoulement obtenu pour les très faibles vitesses de soubassement ressemble au sillage derrière une marche 3D. Pour des vitesses de soubassement plus élevées, l’écoulement de soubassement décolle au niveau du sol et impacte soit le culot ou soit la couche de cisaillement supérieure favorisant le développement des instabilités de type Kelvin-Helmoltz dans ce dernier cas. Enfin, la dernière classe est caractérisée par un sillage comparable à celui d’un corps d’Ahmed. L’ajout de volets déflecteurs à l’arrière du culot engendre une augmentation de la pression au culot pour l’ensemble des classes d’écoulement. Cette augmentation réside principalement dans l’effet de vectorisation de l’écoulement. Un système de contrôle actif est intégré sur une maquette 1/8e géométriquement identique à celle à l’échelle 1/43e et équipée de volets déflecteurs. Deux angles de volet supérieur sont testés afin d’obtenir en moyenne (i) un écoulement naturel attaché à la paroi du volet et (ii) un écoulement naturel détaché du volet. Par rapport au cas sans contrôle actif, des gains sur la traînée sont obtenus pour une certaine gamme de fréquence d’actionnement uniquement dans le cas (ii). Ces gains sont obtenus suite au recollement de l’écoulement sur le volet. Enfin, la robustesse des gains sur la pression au culot est testée avec succès en mettant la maquette en dérapage pour simuler un vent de travers. / This PhD thesis was realized in the scope of a collaboration with Renault Trucks and the LMFA in view of an evaluation of the relevance of active flow control for the drag reduction industrial vehicle. The two main objectives of this experimental work are to analyze the impact of the underbody flow on the wake dynamics and to study a flow control strategy combining inclined flaps (located on the upper and lateral edges of the rear base) with pulsed jet actuators for reducing the aerodynamic drag of a square-back bluff body. The wake development for several underbody velocities ranging from 10% to more than 80% of the free-stream velocity is studied on a simplified truck model at scale 1 :43. Rear base pressure measurements lead to the identification of four flow classes associated with different wake structures highlighted by 2D-3C PIV measurements. The wake of the first flow class obtained for very low underbody velocities looks like that of the wake of a 3D backward facing step. For higher underbody velocities, the underbody flow is separated from the ground impaging either the rear base or the upper shear layer triggering Kelvin-Helmoltz instabilities for this last case. Finally, the fourth class is characterized by a wake comparable to that of the Ahmed body. The implementation of inclined flaps at the rear base increases the base pressure for all classes. This increase is mainly due to the vectoring effect of the flow. An active control system is integrated to a 1 :8 scale model geometrically identical to that of the 1 :43 scale model with flaps. Two upper flap angles are tested to have (i) a natural flow attached to the flap and (ii) a natural flow detached from the flap. In comparison to the case without active flow control, drag reductions are obtained only for a specific range of actuation frequencies only in case (ii). These gains are associated with the reattachment of the flow on the flap. Finally, the robustness of the pressure gains is successfully tested in crosswind conditions.

Diferentes tipos de sólitons têm sido observados em meios ópticos não-lineares, e seus comportamentos individuais descritos pela equação não-linear de Schrödinger e pela equação não-linear de Schrödinger generalizada, em diferentes dimensões e geometrias. Entretando, há situações onde muitos sólitons são gerados formando uma densa rede de sólitons. Nestes casos, é impossível desprezar as interações entre os sólitons e temos que considerar a evolução da estrutura como um todo. A teoria das ondas de choque dispersivas em meios fotorrefrativos e a teoria da difração não-linear de intensos feixes de luz propagando-se em meios fotorrefrativos com um fio refletor incorporado a esse meio foi desenvolvida, e verificamos que está em excelente acordo com nossas simulações numéricas. No caso da formação de sólitons em condensados, fizemos cálculos numéricos realísticos dentro da aproximação de campo médio usando a equação de Gross-Pitaevskii, incluindo também um potencial de confinamento, um potencial móvel e um potencial dipolar. A maioria dos resultados puderam ser comparados com experimentos recentes. / Different kinds of solitons have already been observed in various nonlinear optical media, and their behavior has been explained in the frameworks of such mathematical models as the nonlinear Schrödinger and generalized nonlinear Shrödinger equations for different dimensions and geometries. However, there are situations when many solitons are generated so that they can comprise a dense soliton train. In such situations, it is impossible to neglect interactions between solitons and one has to consider the evolution of the structure as a whole rather than to trace the evolution of each soliton separately. The theory of optical shock waves in photorefractive media and the theory of nonlinear diffraction of light beams propagating in photorefractive media with embedded reflecting wire was developed and agrees very well with our numerical simulations. In the condensate soliton formation case, we did numerical calculations in the mean field approach using the Gross-Pitaevskii equation, adding a trap potential and a moving potential and a potential of the dipole-dipole interaction. The main results were also checked by recent experiments.

Dois dos principais objetivos no estudo da aerodinâmica de veículos comerciais são a redução no consumo de combustível e o aumento na eficiência da refrigeração do motor. Esses objetivos podem ser alcançados através do desenvolvimento de dispositivos que modifiquem o escoamento do ar ao redor do veículo e também através da alteração da forma das superfícies externas. A inclinação das superfícies da parte traseira de um ônibus, por exemplo, tem grande influência sobre a esteira turbulenta que se forma atrás do veículo. O uso de ferramentas computacionais permite uma redução de custo e maior flexibilidade na análise aerodinâmica de autoveículos. Ainda é preciso, no entanto, que o resultado dessas ferramentas computacionais seja verificado com o maior número possível de casos para que se possa escolher e ajustar o modelo matemático de forma adequada. O objetivo do presente trabalho é a verificação dos resultados computacionais e experimentais no desenvolvimento de metodologias que visem à redução no consumo de combustível e aumento na eficiência da refrigeração do motor. Foram comparados resultados experimentais e computacionais do escoamento sobre um modelo de um ônibus comercial em escala 1:17,5. Para a realização do experimento foi utilizado um túnel de vento de seção aberta, onde foram analisadas as distribuições de pressão nas superfícies da carroceria e o arrasto aerodinâmico. Para o teste computacional, foi utilizado um software de dinâmica dos fluidos computacional em que as equações de Navier-Stokes com média de Reynolds são resolvidas pelo método dos volumes finitos usando um modelo de turbulência RNG 'capa' - 'épsilon' / Two main objectives in the study of commercial vehicle aerodynamics are the reduction in fuel consumption and the improvement in engine refrigeration efficiency. These objectives can be achieved through development of devices which vary the flow characteristics around the vehicle and also through modification of the shape of external surfaces. The slope of rear surfaces, for instance, has large influence over the wake turbulence which forms behind the vehicle. The use of computational tools yields cost reduction and greater flexibility in automotive aerodynamic analysis. There is still a need, however, for verification of results, generated by these computational tools, with the largest possible number of test cases so that the mathematical model is adequately chosen and adjusted. The objective of the present work is the verification of experimental and computational results in the development of methodologies aiming at reduction of fuel consumption and improvement in engine refrigeration efficiency. Experimental and computational aerodynamic results were compared for a commercial bus model with a 1:17.5 scale. The experiments were conducted in an open section wind tunnel where pressure distribution and aerodynamic drag were analyzed. The numerical analysis was conducted using computational fluid dynamics software which solves the Reynolds Averaged Navier-Stokes equations using the finite volume method with a RNG 'capa' - 'épsilon' turbulence model

Nesse trabalho, foi analisada a redução de arrasto, a partir da utilização de duas bancadas experimentais, onde uma delas está situada no laboratório de Mecânica dos Fluidos (EPUSP) e a outra, no laboratório de Fisiologia Vascular (ICB-USP). A redução de arrasto foi investigada a partir do uso dos seguintes polímeros: poliacrilamida 1822S e 1340S, polietileno glicol (PEG4000) e óxido de polietileno (Polyox WSR-301). O comportamento reológico das soluções poliméricas do PEG4000 e das poliacrilamidas foi adquirido experimentalmente, enquanto do Polyox WSR-301 foi obtido da literatura. Esses polímeros foram utilizados na bancada experimental da EPUSP, simulador hidrodinâmico, mas somente o PEG4000 foi utilizado na bancada experimental do ICBI em leitos arteriais caudais de ratos normotensos (Wistar) e espontaneamente hipertensos (SHR). No simulador hidrodinâmico, foi estudada a redução de arrasto em escoamentos pulsáteis laminares e turbulentos, cuja faixa de Reynolds varia entre 2300 a 13700, com concentrações poliméricas que variaram entre 5 e 100 ppm, porém para o PEG4000 essa concentração atingiu valor de 5000 ppm. Em leitos arteriais caudais de ratos, a redução de arrasto foi analisada para escoamento laminar, cuja faixa de Reynolds varia entre 100 e 700, com concentração polimérica de 5000 ppm. Além disso, a redução de arrasto foi estudada na presença e ausência das células endoteliais. Simulações computacionais utilizando o método dos volumes finitos (Fluent) foram realizadas a partir dos dados obtidos da bancada experimental do ICB-I, para avaliar a distribuição da tensão de cisalhamento sobre a parede do vaso na presença e ausência das células endoteliais e do PEG4000, considerando a parede da artéria rígida. A partir dos dados obtidos da análise da viscosidade, ficou constatado que o PEG4000 com concentração de 5000 ppm e as poliacrilamidas 1822S e 1340S com concentrações de 5 e 10 ppm apresentaram comportamento de fluido Newtoniano. Para as poliacrilamidas, concentrações poliméricas acima de 10 ppm apresentaram comportamento de fluido não-Newtoniano. De acordo com a literatura, o Polyox WSR-301 apresentou comportamento de fluido Newtoniano para todas as concentrações poliméricas utilizadas nesse trabalho. O PEG4000 não apresentou o fenômeno da redução de arrasto em nenhuma concentração polimérica analisada, quando aplicado na bancada experimental da EPUSP. As poliacrilamidas e o Polyox WSR-301 apresentaram reduções de arrasto que foram dependentes do número de Reynolds e da concentração utilizada, muito embora o Polyox WSR-301 tenha se mostrado mais eficiente em promover esse fenômeno. Nos leitos arteriais caudais, o PEG4000 apresentou redução de arrasto para a concentração de 5000 ppm, que foi acentuada pela presença das células endoteliais. Os valores da tensão de cisalhamento foram maiores para o animal SHR quando comparados com o animal Wistar. Além disso, no animal Wistar, o endotélio controlou o aumento dessa tensão via produção de substâncias vasodilatadoras, mas apresentou disfunção no animal SHR. A partir dos resultados apresentados acima, podese concluir que o Polyox WSR-301 é mais eficiente para promover a redução de arrasto em tubos rígidos. Por outro lado, muito embora o PEG4000 não tenha apresentado efeito na bancada experimental da EPUSP, esse se mostrou um bom redutor de arrasto em leitos arteriais caudais, tendo sua ação intensificada pela presença das células endoteliais. / In this work, the drag reduction was analyzed in two benches located at Laboratory of Fluid Mechanics at Polytechnic School (EPUSP) and at Laboratory of Vascular Physiology at Institute of Biomedical Science (ICB-USP). The drag reduction was investigated for the following polymers: polyacrilamide 1822S and 1340S, polyethylene glycol (PEG4000) and polyethylene oxide (Polyox WSR-301). The rheological behavior of polymeric solutions of polyacrilamide and PEG4000 was acquired experimentally; while it was obtained from the literature for Polyox WSR-301. All of these polymers were used in the hydrodynamic simulator, but only PEG4000 was employed in the tails arterial bed from normotensive (Wistar) and spontaneously hypertensive rats (SHR) at ICB-1. In the hydrodynamic simulator, the drag reduction was analyzed in laminar and turbulent pulsatile flow, in the range varying between 2300 and 13700, with polymeric concentrations between 5 and 100 ppm, but for PEG4000, concentration has reached 5000 ppm. On the other hand, in the tail arterial beds, the drag reduction was analyzed for laminar flow, in the range between 100 and 700, with polymeric concentration of 5000 ppm. In addition, it was studied in the presence and absence of endothelial cells. Computational simulation using the finite volume method (Fluent) was performed using data obtained from ICB-1 in order to analyze the wall shear stress distribution along of wall vessel both in the presence and absence of endothelial cells and PEG4000, considering the rigid walls. Polyacrilamide 1822S and 1340S as well as PEG4000 showed behavior of Newtonian fluid in the following concentrations: 5 and 10 ppm and 5000 ppm, respectively. On the other hand, for polyacrilamides, concentrations higher than 10 ppm showed behaviour of non- Newtonian fluids. According to the literature, the Polyox WSR-301 behaved as a Newtonian fluid in all concentrations used in this work. At EPUSP\'s bench, while PEG4000 did not show drag reduction for any polymeric concentration analyzed, this phenomenon could be seen for polyacrilamides and Polyox WSR-301, being dependent on Reynolds number as well as polymeric concentration. More important, Polyox WSR- 301 showed to be the most efficient drag reducer of them. Interestingly, in the assays employing the tail arterial beds, PEG4000 showed drag reduction in the concentration of 5000 ppm and it was increased by the presence of the endothelial cells. Thus, Polyox WSR-301 seems to be more efficient to promote drag reduction in the rigid tubes. On the other hand, while PEG4000 did not show drag reduction at EPUSP\'s bench, it was a good drag reducer in the tail arterial beds, being intensified by the action of endothelial cells.

O interesse em escoamento bifásico líquido-líquido aumentou recentemente, em especial devido às grandes perdas de energia envolvidas no transporte de petróleo, onde comumente uma mistura bifásica óleo-água é deslocada ao longo de grandes distancias. Embora este tipo de escoamento seja comum na indústria, não existem tantos trabalhos na literatura quanto os relacionados ao escoamento gás-líquido. Alguns estudos sobre escoamentos óleo-água reportam uma redução de atrito em dispersões e emulsões em regime turbulento sem adição de qualquer tipo de substancia química, mas a física por trás do fenômeno ainda não é bem compreendida. Neste trabalho, foi estudado o padrão de escoamento disperso óleo-água em tubulação horizontal, visando a obtenção de novos dados experimentais e um melhor entendimento do fenômeno de redução de atrito. Uma série de parâmetros considerados importantes para a caracterização do escoamento foi investigada: queda de pressão, fração volumétrica e sub-padrões de escoamento disperso. Apresentam-se dados de distribuição das fases e fração volumétrica in situ, obtidos através de um moderno sensor intrusivo, do tipo wire-mesh, baseado em medidas de capacitância (permissividade). Câmera de alta velocidade e técnica das válvulas de fechamento rápido foram utilizadas para validar os sinais do sensor. Um modelo prospectivo simplificado foi desenvolvido como uma tentativa de explicar a ocorrência do fenômeno de redução de atrito no padrão disperso óleo-água estudado. O modelo sugere que a presença de uma fina película de água rente a parede hidrofílica/oleofóbica do tubo poderia explicar a diminuição no gradiente de pressão bifásico observada. / The interest in two-phase liquid-liquid flow has increased recently mainly due to the petroleum industry where oil and water are often produced and transported together for long distances and the significant frictional pressure gradient involved. Liquid-liquid flows are present in a wide range of industrial processes; however, they have not been studied as intensively as gas-liquid flows. Drag reduction phenomenon in oil-water flows without the addition of any drag reduction agent has been detected in previous works, but the physics behind the phenomenon is yet not well understood. The aim of the research was to study the dispersed oil-water flow pattern in a horizontal pipe in order to better understand the phenomenon and the obtaining of new experimental data of oil-water dispersed flows. Important issues related to oil-water pipe flow were investigated: pressure drop, volume fraction and flow patterns. Phase distribution and holdup data were obtained by a new wire-mesh sensor based on capacitance (permittivity) measurements. A high-speed video camera and the Quick-Closing-Valves technique were used to compare and validate the signals of the wire-mesh sensor. A simplified mathematical model was proposed to explain the drag reduction phenomenon in the oil-water dispersed flow studied. The model suggests that the presence of a thin water film between the homogenously dispersed flow and the pipe wall could explain the observed decreases of the two-phase pressure gradient.