O escoamento de um fluido ao redor de corpos rombudos configura-se em um dos principais problemas da mecânica dos fluidos. As investigações deste fenômeno são baseadas em técnicas analíticas, numéricas e experimentais. Cada abordagem apresenta suas vantagens e desvantagens, sendo impossível a plena caracterização do escoamento através de uma única técnica para a maioria das geometrias de corpo e condições de escoamento. É neste contexto que se insere esta tese, que compreende um estudo fundamental sobre a dinâmica de formação e desprendimento de vórtices baseado em técnicas experimentais. Primeiramente, realiza-se um estudo de estabilidade hidrodinâmica do escoamento em torno de cilindro circular via modelo de Ginzburg-Landau. Os resultados experimentais deste estudo serviram para validar simulações numéricas e a principal técnica experimental utilizada foi a Velocimetria por Imagem de Partículas (PIV). A decomposição de campos de velocidade em série de Fourier permite verificar a hierarquia sugerida pela solução assintótica da bifurcação de Hopf. Além disso, os resultados também indicam quando a tridimensionalidade passa a ser importante no escoamento. A tridimensionalidade do escoamento está intimamente ligada ao fenômeno de vibração induzida por vórtices (VIV), que exerce efeitos danosos em uma grande quantidade de estruturas sujeitas a escoamentos fluidos. Com o objetivo de suprimir as VIV, realizou-se um estudo paramétrico do supressor do tipo strakes helicoidal, que é bastante empregado na indústria offshore. Verificou-se que os strakes modificam as características tridimensionais da esteira de um cilindro. Apesar da eficiência dos strakes na supressão de VIV, eles possuem algumas limitações inerentes às características hidrodinâmicas do escoamento. Sendo assim, apresenta-se uma técnica que reduz as tridimensionalidades de modo a tornar o escoamento bidimensional, com a possibilidade de controle ativo de malha fechada. O método de controle de camada limite por superfícies móveis (CCLSM) suprime VIV e diminui o arrasto atrasando a separação da camada limite do cilindro através da injeção de quantidade de movimento angular pelos cilindros de controle rotativos. / The fluid flow around bluff bodies is one of the main problems in fluid mechanics. The investigations of this phenomenon are based on analytical, numerical and experimental techniques. Each technique presents advantages and disadvantages, being impossible the comprehensive characterization of the flow though only one technique for the majority of body geometries and flow conditions. Within this context, the present thesis is proposed, which comprehends a fundamental study about the vortex shedding dynamics based on experimental techniques. Firstly, a hydrodynamic stability study of the flow around a circular cylinder is performed using the Ginzburg-Landau model. The experimental results of this study allowed the validation of numerical simulations and the main experimental technique employed was the Particle Image Velocimetry (PIV). The Fourier series decomposition of velocity fields permits to verify the hierarch suggested by the asymptotic solution of the Hopf bifurcation. Additionally, the results also indicate when the three-dimensionalities become important in the flow. The flow three-dimensionality is closely associated to the vortex-induced vibration (VIV) phenomenon, which exerts damaging effects on a great quantity of structures subjected to fluid flows. In order to suppress VIV, it was realized a parametric investigation of the helical strakes, that are commonly employed in the offshore industry. One verifies that the strakes modify the three-dimensional characteristics of the cylinder wake. Despite of the strake efficiency regarding the VIV suppression, the strakes have some limitations that are inherent to the flow hydrodynamic features. Consequently, it is presented a technique that reduces the three-dimensionalities in order to create a two-dimensional flow, with the possibility of closed-loop active control. The moving surface boundary-layer control (MSBC) suppresses VIV and reduces the drag delaying the cylinder boundary-layer separation through the injection of angular momentum by the rotational control cylinders.

Embora seja uma técnica tradicional, empregada largamente em processos industriais, a operação unitária de aeração pode ser otimizada ao se utilizar modelos matemáticos que descrevam seu comportamento hidrodinâmico. Diversas equações se prestam a esse fim, no entanto, avanços tecnológicos, tanto no campo instrumental como computacional, permitiram a obtenção de equações mais realísticas e abrangentes. Neste trabalho foram ajustadas e avaliadas equações para descrever três importantes parâmetros envolvidos na transferência de oxigênio em meio hídrico: coeficiente volumétrico de transferência de massa, fração de vazios e velocidade ascensional de bolhas. Para tanto, ademais da utilização de conceitos teóricos amplamente difundidos no meio acadêmico, empregou-se um conjunto de dados já existente. Essa combinação permitiu a avaliação e aproximação das equações teóricas à realidade experimental através de coeficientes de ajuste empíricos. Foram obtidos os seguintes resultados: a) revisão bibliográfica e sugestão da correlação que melhor descreve o coeficiente volumétrico de transferência de massa; b) correlação que descreve a fração de vazios, a partir da analise da concentração de bolhas segundo distribuições gaussianas; c) correlação que descreve a velocidade ascensional de bolhas em plumas. A complexidade de cada parâmetro obtido deixou clara a importância da análise isolada, precedendo a convolução dos mesmos em um único modelo, pois embora as resposta e recomendações apresentadas não forneçam conclusões definitivas sobre todos os aspectos envolvidos na transferência de oxigênio em meio hídrico, suas considerações pontuais contribuem sobremaneira ao domínio do fenômeno global, beneficiando modelagens matemáticas futuras. / Although it is a traditional technique, widely employed in industrial processes, the unit operation of aeration can be optimized when resorting to mathematical models which describe their hydrodynamic behavior. A range of equations lends itself to this purpose, however, technological advances both in the instrumental as computational field, allowed the achievement of equations more realistic and comprehensives. In this study were adjusted and evaluated equations to describe three important parameters involved in the oxygen transfer in the hydric medium: volumetric mass transfer coefficient, void fraction and upflow bubble velocity. To this end, besides the use of theoretical concepts widely disseminated in the academic literature, it was employed a set of already existing data. This combination allowed the evaluation and approximation of theoretical equations to experimental reality by means of empirical adjustment coefficients. Were obtained the following results: a) literature review and suggestion of the best correlation which describes the volumetric mass transfer coefficient, b) correlation which describes the fraction of voids, from the analysis of the concentration of bubbles by Gaussian distributions, c) correlation which describes the upflow velocity of swarms of bubbles. The complexity of each parameter obtained made clear the importance of the isolated analysis, preceding the convolution of them in a single model because although the answers and recommendations given fail to supply definitive conclusions on all aspects involved in the transfer of oxygen in hydric medium, their specific considerations contribute to the knowledge of the global phenomenon, benefiting deeply future mathematical models.

Cette thèse porte sur l’étude expérimentale de la réduction de traînée par injection de bulles. Le contexte de l’étude est lié à la propulsion navale. Les bulles peuvent, lorsqu’elles sont injectées dans la couche limite en développement le long des carènes de navires, contribuer à réduire significativement la résistance de frottement, en allégeant d’une part le fluide le long de la coque et d’autre part en interagissant avec les structures turbulentes de proche paroi. La configuration expérimentale retenue pour cette étude est l’écoulement de Taylor-Couette, avec cylindre extérieur fixe et injection de bulles calibrées. Nos investigations portent sur les régimes de transition, de turbulence naissante et turbulent avec persistance des cellules de Taylor (Re≤20.104). La taille des bulles varie avec le capillaire et le mélange utilisés, entre 0,05 et 0,12 fois la largeur de l’entrefer. Une méthode originale de suivi de la phase dispersée dans un plan méridien, couplée à des mesures de couple global appliqué au cylindre intérieur ont permis de mettre en évidence deux régimes de réduction de traînée et plusieurs types d’arrangements des bulles, en fonction de leur taille et du nombre de Reynolds. Les bulles peuvent avoir une trajectoire glissante, oscillante, être capturées par les cellules de Taylor ou en proche paroi du cylindre intérieur dans les zones de jets sortants. La caractérisation par PIV des vitesses de la phase liquide en monophasique et diphasique a permis d’étudier les modifications induites par les bulles sur la phase liquide et de discuter des mécanismes impliqués dans la modification du couple global par la présence des bulles. Il ressort de cette étude que pour les nombres de Reynolds en deçà de la capture, les bulles contribuent à stabiliser l’écoulement en accord avec une réduction du couple visqueux pouvant atteindre -30% pour des taux de vide très faible (< 1%). Pour des nombres de Reynolds plus élevés, la capture dans les cellules conduit à une réduction de la longueur d’onde axiale et une augmentation de la vorticité des cellules, associée à une augmentation des vitesses rms. Cette configuration est favorable à une augmentation du couple visqueux. A l’inverse, la capture des bulles dans le jet sortant conduit à une augmentation de la longueur d’onde axiale, associée à une diminution de la vorticité. Cette configuration est favorable à une réduction du couple visqueux, moins marquée qu’en absence de capture. / This work presents experimental study of drag reduction by injection of bubbles. Injection of bubbles into the developing boundary layer along the hulls of ships could help to reduce significantly the frictional resistance by lowering a fluid along the hull and interacting with the near-wall turbulent structures. We investigate the interactions between bubbles, the coherent motion and the viscous torque in a Taylor-Couette flow for outer cylinder at rest, while bubbles are injected constantly through a needle. The Reynolds number ranges up to Re≤20.104, for these values of the Reynolds number, Taylor vortices are persistent leading to an axial periodicity of the flow. Bubbles size varies between 0.05 and 0.12 times the width of the gap, depending on the needle and the liquid used. An original method for tracking bubbles in a meridian plane coupled with measures of overall torque applied to the inner cylinder helped to highlight two regimes of drag reduction and various types of arrangements of bubbles, depending on their size and Reynolds number. Bubbles could have a sliding motion, wavering, be captured by the Taylor cells or in the outflow areas near the inner cylinder. Characterization of the liquid velocity by PIV both in single phase and two-phase flow helped to study the modifications induced by the bubbles on the liquid phase and to discuss about the mechanisms involved in the changes induced by the bubbles in the overall torque. The study show that for the Reynolds number before the capture, bubbles could help to stabilize the flow in agreement to the reduction of the viscous torque up to -30% for lowest void fraction (<1%). For the Reynolds number after the capture, bubbles trapped by the Taylor cells lead to a reduction of the axial wavelength and increasing of the vorticity of the cells, associated to an increasing of the rms. This configuration leads to an increasing of the viscous torque. However, bubbles trapped in the outflow areas near the inner cylinder lead to an increasing of the axial wavelength, associated to a decreasing of the vorticity. The configuration supports a smaller reduction of the viscous torque than in the case without captured.

Ce manuscrit présente les travaux de thèse réalisés dans le cadre d’une convention CIFRE entre Renault Trucks et le LMFA. Une stratégie de contrôle d’écoulement, associant un volet déflecteur et des actionneurs de type jets pulsés et synthétiques, est étudiée expérimentalement en vue de réduire la traînée aérodynamique de corps non profilés à culot droit. Une première approche consiste à étudier l’influence de cette stratégie sur une maquette bidimensionnelle. Des mesures de vitesse dans le sillage proche par TR-PIV et par anémométrie à fil chaud démontrent qu’une certaine gamme de fréquence d’actionnement permet à l’écoulement de recoller sur le volet et de diminuer les fluctuations de vitesse dans la zone de recirculation, ce qui engendre une augmentation de la pression au culot. Une analyse par moyenne de phase et la détermination de corrélations spatio-temporelles permettent d’identifier les perturbations induites par le contrôle conduisant à ces modifications de l’écoulement. Un système de jets synthétiques est ensuite intégré à une maquette simplifiée de véhicule poids lourd à l’échelle 1/8e, dont le sillage est représentatif des remorques réelles. Des gains en traînée significatifs sont obtenus et sont associés aux mêmes phénomènes aérodynamiques que pour la maquette bidimensionnelle. Enfin, une étude paramétrique montre la robustesse du contrôle aux caractéristiques de la couche limite incidente aux jets et à la longueur du volet déflecteur. / This document presents the research work realized in the scope of a PhD thesis with Renault Trucks and the LMFA. A flow control strategy, combining an inclined flap with pulsed or synthetic jets, is experimentally studied to reduce the aerodynamic drag of square-back bluff bodies. A first approach consists in studying the effect of this strategy on the flow behind a twodimensional model. The near-wake flow is characterized by the use of velocity measurements obtained by Time-Resolved Particles Image Velocimetry and hot-wire Anemometry. These measurements show that the increase in rear base pressure, obtained in a specific range of actuation frequencies, is associated with the reattachment of the flow on the flap and with a decrease in velocity fluctuations within the recirculation area. A phase average analysis and the determination of space-time correlations allow identifying the aerodynamic disturbances induced by the control system and leading to these modifications of the wake flow. A synthetic jet system is integrated to a 1 :8 scale simplified truck model, with a wake flow similar to this of real trailers. Significant drag reductions are obtained using active control and are associated with the same flow phenomena as these observed in the two-dimensional model study. Eventually, a parametric study is performed and shows the robustness of the flow control strategy to the characteristics of the boundary layer developing on the model roof and to the flap length.

On considère les paquets d'ondes hydrodynamiques comme mécanismes de génération de bruit des jets subsoniques. Cette approche résulte tout d'abord de l'analyse de données numériques - DNS d'une couche de mélange (Wei et Freund 2006) et LES d'un jet à Mach 0,9 (Daviller 2010) - permettant de déterminer les propriétés des sources en termes de compacité, d'intermittence et de structure azimutale. L'identification d'un rayonnement intermittent associé aux modifications des structures cohérentes des écoulements permet de proposer un modèle de paquet d'onde pour représenter ce phénomène dans l'analogie de Lighthill, dont l'enveloppe présente des variations temporelles d'amplitude et d'étendue spatiale. Celles-ci sont tirées de données de vitesse de simulations numériques de jets subsoniques, et un accord de l'ordre de 1,5dB entre le champ acoustique simulé et le modèle confirme sa pertinence. L'exploration du concept proposé est ensuite poursuivie expérimentalement, avec des mesures de pression acoustique et de vitesse de jets turbulents subsoniques, permettant la décomposition des champs en modes de Fourier azimutaux. On observe l'accord des directivités des modes 0, 1 et 2 du champ acoustique avec le rayonnementd'un paquet d'onde. Les modes 0 et 1 du champ de vitesse correspondent également à des paquets d'onde, modélisés comme des ondes d'instabilité linéaires à partir des équations de stabilité parabolisées. Finalement, des corrélations de l'ordre de 10% entre les modes axisymétriques de vitesse dans le jet et de pression acoustique rayonnée montrent un lien clair entre les paquets d'onde et l'émission acoustique du jet. / Hydrodynamic wavepackets are studied as a sound-source mechanism in subsonic jets. We first analyse numerical simulations to discern properties of acoustic sources such as compactness, intermittency and azimuthal structure. The simulations include a DNS of a two-dimensional mixing layer (Wei and Freund 2006) and an LES of a Mach 0.9 jet (Daviller 2010). In both cases we identify intermittent radiation, which is associated with changes in coherent structures in the flows. A wave-packet model that includes temporal changes in amplitude and axial extension is proposed to represent the identified phenomena using Lighthill's analogy. These parameters are obtained from velocity data of two subsonic jet simulations, and an agreement to within 1.5dB between the model and the acoustic field of the simulations confirms its pertinence. The proposed mechanism is then investigatedexperimentally, with measurements of acoustic pressure and velocity of turbulent subsonic jets, allowing the decomposition of the fields into azimuthal Fourier modes. We find close agreement of the directivities of modes 0, 1 and 2 of the acoustic field with wave-packet radiation. Modes 0 and 1 of the velocity field correspond also to wavepackets, modelled as linear instability waves using parabolised stability equations. Finally, correlations of order of 10% between axisymmetric modes of velocity and far-field pressure show the relationship between wavepackets and sound radiated by the jet.

Le contrôle d’écoulement permet d’éliminer le phénomène de décollement de couches limites, très néfaste pour les performances des machines interagissant avec un fluide (avions, voitures, turbomachines ...). Ces travaux s’intéressent plus particulièrement au contrôle actif d’écoulement au moyen de jets continus. Une maquette permettant de manipuler l’équilibre de la couche limite a été conçue et installée dans la soufflerie du Laboratoire de Mécanique de Lille. La première partie du travail a consisté en la caractérisation de l’écoulement autour du modèle à l’aide de visualisations par fils de laine et par enduit gras, de mesures de répartition de pression, de mesures par anémométrie à fils chauds et par PIV. Ceci a permis de définir la configuration du modèle la plus appropriée pour les études de contrôle mais aussi de connaître précisément les caractéristiques de l’écoulement sélectionné. La configuration retenue correspond à un écoulement en gradient de pression adverse suivi d’une séparation sur le volet, un peu comme sur l’extrados d’une aile d’avion. L’utilisation de sondes de frottement associées à des visualisations aux fils de laine ont permis d’étudier et d’optimiser des actionneurs passifs, puis des actionneurs à jets continus. Certaines des configurations actives optimales ont ensuite été caractérisées plus en détail par une mesure par PIV englobant toute la zone de séparation. Il apparaît que les jets continus ne suppriment pas complètement les mécanismes de la séparation mais réduisent leur intensité et les concentrent plus ou moins près de la paroi / Flow control allows to suppress boundary layers separation, which largely deteriorates the performances of machineries which interact with fluid (aircraft, cars, turbomachineries, etc.). This study concentrates more particularly on active flow control with continuous jets. A ramp model which allows to manipulate the boundary layer equilibrium was realized and set in Laboratoire de Mécanique de Lille wind tunnel. The first part of the work was to characterize the flow over the model with wool-tufts and oil-film visualisations, pressure distribution, hot-wire anemometry and PIV measurements. The aim was to define a ramp configuration for the flow control study and to know precisely the characteristics of the retained flow. The selected configuration corresponds to an adverse pressure gradient flow followed by a separation on the flap, which mimics the flow on the suction side of a wing. With friction probes coupled with wool-tufts visualisations, passive actuators and active continuous jets were studied and optimised. Finally, some of the optimum active configurations found were characterized in more details with PIV measurements over the entire separated region. It appears that continuous jets do not suppress the separation mechanisms, but only reduce their intensity and squeeze them more or less against the wall

Dans ce travail, des écoulements liquide-liquide dispersés homogènes (c'est-à-dire sans gradient de concentration) ont été étudiés dans une conduite horizontale de 7.5m de long et de 50mm de diamètre interne. Les expériences ont été réalisées dans une large gamme de paramètres opératoires (vitesses de mélange comprises entre 0.28 et 1.2m/s et concentration volumique en phase dispersée, f, de 0.08 à 0.7). Le facteur de frottement de ces écoulements a été mesuré et modélisé en régime turbulent, intermédiaire et laminaire. Ces différents régimes ainsi que l’effet de la concentration en phase dispersée ont été identifiés à partir des mesures locales de vitesse par une technique de vélocimétrie par image de particules (PIV). Lorsque f=0.56, les dispersions se comportent comme des fluides newtoniens auxquels le concept de viscosité effective peut s’appliquer. Le modèle de viscosité de Krieger et Dougherty (1959) décrit l’ensemble des émulsions formées. Le facteur de frottement mesuré suit les lois de frottement classiques en régime laminaire et turbulent (Hagen-Poiseuille et Blasius respectivement) en fonction du nombre de Reynolds basé sur les propriétés de mélange des émulsions (densité et viscosité). Toutefois, la concentration en phase dispersée induit un retard à l’apparition de la turbulence. En milieu très concentré (f=0.7), la dispersion a un comportement rhéofluidifiant et suit la loi d’Ostwald avec un exposant, n=0.5. Tous ces écoulements ont été étudiés, en détail, par l’analyse locale des vitesses. / Homogeneous dispersed flows have been investigated in a horizontal pipe (7.5m long and 50mm internal diameter) in a wide range of flow parameters (mixture velocity from 0.28 to 1.2m/s and concentration, f, up to 0.7). In this work, the wall friction of this emulsion has been measured and modeled in turbulent, intermediate and laminar regime. The different flow regime and the effect of dispersed phase volume fraction have been determined from the velocity profiles measured by PIV measurements in a refractive index matched medium. When f=0.56, emulsion behaves as newtonian fluid. It was shown that the concept of effective viscosity is relevant to scale the wall friction of the emulsion flow. The effective viscosity follows the classical trend of low inertia suspension of hard spheres (Krieger &amp; Dougherty 1959). The friction factor is described by the classical single phase laws in turbulent and laminar regime (Hagen-Poiseuille and Blasius respectively) as a function of Reynolds number based on mixture properties (density and viscosity). Compared to single phase flow, the transition to turbulence is delayed as dispersed phase fraction is increased. For higher dispersed phase fraction (f=0.7), emulsion behaves as a shear-thinning fluid. Emulsion follows the Ostwald law with an exponent equal to 0.5. All these homogeneous dispersed flow have been studied in details.

La détermination du champ de pression dans un écoulement et/ou des efforts sur un profil en mouvement à partir de mesures de vitesses effectuées dans le milieu fluide est une problématique actuelle qui intéresse de nombreux domaines de recherche en mécanique des fluides. On pourrait citer en particulier, les systèmes de récupération d'énergie (éolienne, hydrolienne) ou bien les systèmes de contrôle optimal d'aubes de guidage de turbine, etc…Dans ce mémoire, nous apportons notre contribution à ce problème en proposant dans un premier temps, une méthode originale qui permet, à partir de champs de vitesses instationnaires obtenus par mesure optiques PIV, d'approcher ces champs dans l'ensemble du milieu (profil inclus) en utilisant la théorie des polynômes orthogonaux de Legendre. L'équation de Navier-Stokes permet alors d'obtenir des gradients de pression polynomiaux dans l'ensemble du milieu fluide et de pouvoir ainsi calculer le champ de pression dans l'écoulement et ensuite, en utilisant l'équation de bilan de mouvement dans un domaine de référence judicieusement choisi, de déterminer les efforts sur un profil mobile en oscillation. Cette méthode est alors validée sur un profil fixe à partir de données simulées numériquement et de données expérimentales.Dans un deuxième temps, après une série de mesures optiques PIV sur un profil NACA0015 soumis à différents types d'oscillations, nous appliquons la méthode décrite précédemment pour reconstruire les champs de pressions instationnaires et évaluer les efforts instantanées et moyens sur le profil. L'étude d'un certain nombres de plages de fréquences et d'amplitudes permet de comparer nos résultats, pour la recherche d'une meilleure efficacité. / The determination of the pressure field in a flow and/or forces on a moving profile from measurements of velocities carried out in the fluid is a current problem that is of interest to many domains of research in fluid mechanics like the energy recovery systems (wind, hydro) or the speed control of hydraulic turbines, etc…In this PhD thesis, we make a contribution to this problem by initially proposing an original method which allows us to approach unsteady velocity fields in the whole of the flow obtained by PIV optical measurements (including the profile) using Legendre's orthogonal polynomial theory. The Navier-Stokes equations then make it possible to obtain polynomial pressure gradients in the whole of the fluid and thus to be able to calculate the pressure field in the flow by using the momentum balance equation in a judiciously chosen reference range, to determine the forces on an oscillating mobile profile. This method is then validated on a fixed profile using numerically simulated data and experimental data.In a second step, from series of flow PIV measurements on a NACA0015 profile subjected to different types of oscillations, we apply the method described above to reconstruct the unsteady pressure fields and to evaluate the instantaneous and average forces on the profile. The study of a certain number of ranges of frequencies and amplitudes makes it possible to compare our results, in order to seek a better efficiency.

Submitted by biblioteca unifenas (biblioteca@unifenas.br) on 2018-03-05T22:12:22Z No. of bitstreams: 1 Sávio Carneiro Martins Dissertacao.pdf: 1917056 bytes, checksum: 1e6b06de6f8c419963c162ad0230fffa (MD5) / Made available in DSpace on 2018-03-05T22:12:22Z (GMT). No. of bitstreams: 1 Sávio Carneiro Martins Dissertacao.pdf: 1917056 bytes, checksum: 1e6b06de6f8c419963c162ad0230fffa (MD5) Previous issue date: 2015-03-30 / Due to the importance of in vitro embryo production (IVEP) to accelerate genetic improvement is important the search for technological innovation that can enhance the in vitro embryo development. Mouse embryonic fibroblasts (MEFs) have been widely used as a feeder layer to support embryonic stem cells due to their release of growth factors. Mesenchymal stem cells (MSCs) from different sources were also found to release bioactive factors that can support cell growth. This study aims to investigate the effect of co-culture of MSC from rat bone marrow or MEF as a feeder source for in vitro production of bovine embryos. Cumulus oophorus complexes were matured into three groups: control (CTRL), co-culture with monolayer of mesenchymal cells of rats (MSC) or co-cultured with monolayer of embryonic fibroblasts of mice (MEF). Fertilization was performed in control condition for all groups, and in vitro fertilized embryos were cultured from fourth day on in CTRL, co-culture with MSC or co-cultured with MEF, so that the following groups were performed: (CTRL / CTRL) - maturation and embryo development in CTRL conditions; (CTRL / MSC) - maturation in CTRL and embryo development with MSC from the fourth day on after the beginning of the in vitro embryo culture; (CTRL / MEF) - maturation CTRL and embryo development with MEF from the fourth day on after the beginning of the in vitro embryo culture; (MSC / CTRL) - MSC during maturation and embryo development in CTRL; (MSC / MSC) - maturation and embryo development in MSC from the fourth day on after the beginning of the in vitro embryo culture; (MEF / CTRL) - maturation and embryo development in MEF and CTRL (MEF / MEF) - maturation and embryo development in MEF from the fourth day on after the beginning of embryo development in vitro. No significant difference was found among the oocytes matured in CTRL, MSC and MEF conditions for metaphase II and apoptosis rates and for cleavage rate in embryos at 4th day after the beginning of the in vitro culture. The number of cells in the inner cell mass, trophoblast cells, apoptotic cells and total cells were similar (P> 0.05) in the embryos from all experimental groups. The rates of blastocyst formation, expanded, hatched and the total of blastocysts did not differ among experimental groups (P> 0.05) at 7th day of embryo development. At eighth day of embryo culture we observed a difference (P <0.05) in hatched blastocyst rate which was higher in the CTRL /CTRL group when compared to MSC/MSC group, however, the proportion of blastocyst, expanded and total blastocysts was not different (P> 0.05). We conclude that there was no significant improvement in bovine embryo development using co-cultures of MSC from rats or MEF when compared to control culture system. However more studies investigating the use of stem cells from other sources or their conditioned medium are needed to better understand the effect of these cells on embryonic development. / Diante da importância da produção in vitro de embriões (PIVE) na expansão do melhoramento genético, é importante a busca de inovações tecnológicas que possam potencializar o desenvolvimento embrionário in vitro. Fibroblastos embrionários de camundongo (MEFs) têm sido amplamente utilizados como camada alimentadora para suportar as células-tronco embrionárias, devido à sua liberação de fatores de crescimento. As células-tronco mesenquimais (MSCs) identificadas a partir de diferentes fontes, também liberam fatores bioativos que possam suportar o crescimento celular. Este estudo tem como objetivo investigar o efeito da co-cultura de MSC de medula óssea de rato ou MEF como fonte alimentadora na produção in vitro de embriões bovinos. Complexo cumulus oophorus foram maturados em três grupos distintos: Controle (CTRL), co-cultura com monocamada de células mesenquimais de ratos (MSC) ou co-cultura com monocamada de fibroblastos embrionários de camundongos (MEF). A fecundação foi realizada em condição controle para todos os grupos e os embriões fecundados in vitro foram também cultivados a partir do quarto dia em CTRL, co-cultura com MSC ou co-cultura com MEF, formando os seguintes grupos experimentais: (CTRL/CTRL) – maturação e cultivo embrionário em condições CTRL; (CTRL/MSC) – maturação em CTRL e cultivo embrionário em MSC a partir do quarto dia após o início do cultivo embrionário in vitro; (CTRL/MEF) – maturação em CTRL e cultivo embrionário em MEF a partir do quarto dia após o início do cultivo embrionário in vitro; (MSC/CTRL) – maturação em MSC e cultivo embrionário em CTRL; (MSC/MSC) – maturação e cultivo embrionário em MSC a partir do quarto dia após o início do cultivo embrionário in vitro; (MEF/CTRL) – maturação em MEF e cultivo embrionário em CTRL e (MEF/MEF) – maturação e cultivo embrionário em MEF a partir do quarto dia após o início do cultivo embrionário in vitro. Nenhuma diferença significativa foi encontrada entre os oócitos dos grupos CTRL, MSC e MEF, na taxa de estruturas em metáfase II, apoptose e clivagem nos embriões de 4 dias após o início do cultivo in vitro. O número de células da massa celular interna, células do trofoblasto, células em apoptose e células totais foram iguais (P>0,05) entre os embriões dos diferentes grupos experimentais. As taxas de embriões em estágio de blastocisto, blastocisto expandido, blastocisto eclodido e blastocistos totais dos grupos experimentais não se diferiram (P>0,05) no sétimo dia de cultivo embrionário. No oitavo dia de cultivo embrionário houve diferença (P<0,05) da taxa de blastocisto eclodido, sendo maior no grupo CTRL/CTRL quando comparado ao grupo MSC/MSC; no entanto, a proporção de blastocisto, blastocisto expandido e blastocistos totais não foram diferentes (P>0,05) entre os grupos experimentais. Concluímos que não houve melhora significativa no desenvolvimento embrionário bovino utilizando co-culturas com MSC de ratos ou MEF de camundongos, quando comparado com sistema de cultura controle. Entretanto, mais estudos investigando o uso de células-tronco de outras fontes ou seu meio condicionado são necessários para se entender melhor o efeito destas células no desenvolvimento embrionário.

[pt] O presente trabalho tem por objetivo a realização de experimentos e simulações numéricas para estudar a interação da turbulência e da combustão em uma chama não pré-misturada de hidrogênio no ar estabilizada a jusante de um corpo rombudo. Para tanto, são utilizadas, simultaneamente, as técnicas de PIV, para a determinação de dois componentes da velocidade, e a técnica de PLIF para a determinação da intensidade de fluorecência do radical químico OH, que é um bom indicador da localização da frente de chama. São avaliados os métodos de pós processamento dos resultados do PIV com o intuito de maximizar a resolução espacial da técnica e ao mesmo tempo remover o maior número de vetores espúrios dos campos de velocidade instantâneos. Paralelamente, o queimador é modelado no software ANSYS/FLUENT e os resultados de simulação validados por comparação com os resultados experimentais. Modelos baseados nas médias de Reynolds são empregados para a caracterização da turbulência e o modelo de elementos de chama é adotado para a descrever a combustão. Os resultados experimentais indicam que, para as vazões de ar e hidrogênio adotadas, a combustão ocorre no regime de elementos de chama, onde a frente de chama apresenta algumas dobras, mas sem descontinuidades. Os resultados das simulações com combustão não obtiveram boa concordância com os resultados experimentais, indicando que a malha de cálculo precisa ser aprimorada. / [en] The aim of this work is to carry out experiments and numerical simulations to study the turbulence-combustion interaction in a nonpremixed hydrogen-air ame stabilized in a bluff body wake. For this purpose, are used a PIV technique for the determination of two velocity components and a PLIF technique to determine the uorescence intensity of the chemical species OH, which is a good indicator of the flame front location. PIV post-processing methods are evaluated in order to maximize the spatial resolution of the technique and to remove spurious instantaneous velocity vectors. In addition, the burner is modeled in ANSYS / FLUENT and the simulation results are validated by comparisons with the experimental results. Models based in the Reynolds avareges are used to characterize the turbulence and a flamelet model is adopted to describe combustion. The experimental results indicates that, for the ow rates of air and hydrogen adopted, combustion occurs in the flamelet regime, where the flame front is wrinkled, but without discontinuities. The reactive cases simulations did not agree with the experimental results, indicating that the computational mesh needs to be improved.