Les problèmes associés au transport sédimentaire sont l'une des préoccupations majeures de notre société, tant d'un point de vue environnemental qu'économique. Nous disposons de peu d'informations sur la dynamique locale des phénomènes d'érosion et plus particulièrement pour les sédiments cohésifs. Dans cette étude, nous nous focalisons sur les phénomènes locaux agissant à l'interface eau-sédiment. Tout d'abord, un sédiment modèle transparent est réalisé en nous basant sur les propriétés rhéologiques des sédiments naturels. Pour cela, différents mélanges, à base de Laponite et de carboxyméthylcellulose, sont testés en faisant varier la concentration et le mode de fabrication. Les protocoles de mesures sont alors établis et une loi d'évolution des propriétés en fonction de la concentration en sédiment est déterminée. Puis, la qualification de la veine hydraulique de l'étude, sans présence de sédiment, est réalisée par des mesures optiques PIV. L'obtention des champs de vitesse moyens et instantanés nous a permis de calculer l'énergie cinétique turbulente ainsi que les contraintes laminaires et turbulentes agissant sur le fond. Enfin, des mesures similaires sont effectuées dans le canal en présence de sédiment pour des cas où le sédiment est entraîné ou non par les forces hydrodynamiques. L'accès à l’énergie cinétique turbulente ainsi qu'aux contraintes laminaires et turbulentes hydrodynamiques permet de comprendre les phénomènes locaux étant à l’origine de l'érosion. Les contraintes à l'interface sont comparées à celles obtenues dans le sédiment via la loi rhéologique mettant en évidence la présence d'une contrainte de cisaillement critique liée aux propriétés du sédiment. / Associated problems with sediment transport are one of the major concerns of our society, as an environmental and economic perspective. Few information about local dynamics of erosion is available and especially for cohesive sediments. In this study, we focus on local phenomena acting at the water-sediment interface. First, a transparent sediment model is made based on rheological properties of natural sediments. For this purpose, different mixtures, containing Laponite and carboxymethylcellulose, are tested by varying the concentration and method of manufacture. Measurement protocols are then established and a law of variation of rheological properties as a function of the sediment concentration is determined. Then, definition of flow within the hydraulic channel of the study, without the presence of sediment, is obtained by PIV optical measurements. Average and instantaneous velocity fields allowed us to calculate the turbulent kinetic energy and the laminar and turbulent stresses acting on the bottom. Finally, similar measurements are carried out in the channel with presence of sediments in cases where the sediment is driven or not by hydrodynamic forces. Access to the turbulent kinetic energy as well as laminar and turbulent hydrodynamic stresses provides an understanding of local phenomena causing erosion. Stresses at the interface are compared with those obtained within the sediment via the rheological law highlighting the presence of a critical shear stress related to the sediment properties.

Development of civilization faces a challenge of developing the resources of energy demand for the modern life. Extensive use of conventional fuel resources like crude oil and coal rise up a serious problem of increasing CO2 emission. New records levels of CO2 were registered during the early beginning of industrial revolution (http://climate.nasa.gov/evidence). Now a day’s more attention is oriented towards developing of biomass power stations owing to the increasing of conventional fuel prices and due to the potential to be CO2 neutral. One of the essential issues to successfully simulate and design efficient equipment for best utilization of the bio-fuel is to have better understanding of the interaction of bio-particles and the carrier gas. Almost, all two-phase flow system dealing with bio-mass power is turbulent flow. A unifying theory of turbulence does not yet exist. When particles are suspended into such a flow the flow becomes even more complicated and the resulting interactions between the particles and turbulent structures are not fully understood. For non-spherical particles, like most of the bio-mass particles found in cyclone filters and biomass gasification and combustion, the interactions of the particles and the fluid in turbulent flow are extremely complex while theories exists for low Reynolds number flow. The carrier phase turbulence alters the dispersed phase translational and rotational motion and the particles influence the detailed and overall flow of the carrier phase. The presence of the particles may also modify the turbulence of the fluid.To achieve my objective, to study the interaction of bio-particles with the carrier phase, and because of the complexity of the mechanisms related to such flow, it was essential to start to develop the knowledge on the possible mechanisms for the interactions and the importance of each of these interactions, see Paper A. Also, the controlling parameter which may have qualitative and/or quantitative influence of the flow interaction is covered by Paper A. To enable different types of experiments with PIV and LDA, a horizontal rectangular duct was designed and constructed. Design details and test is presented in Paper B. An introductory experimental series was performed in the current set-up using a high spatial resolution PIV system and the results can be found in Paper C.

This theses deals with flow of two immisible fluid in horizontal pipeline. First part teoretically describes immisible flow. What follows is experimental measurement in wich experimental track was adjusted for inlet of oil from the top. Water and corn germ oil were used as fluids. There were observed many modes of flow on the track. After that PIV was described and measured. PIV was done for measurement of values of velocity vectors. Simulation of one chosen mode was developed in the last chapter. This simulation was done in Ansys Fluent with help of VOF method. Simulation was done both in 3D and 2D pipeline. In the end these simulation were compared with experiment measurement and were critically evaluated.

Ce travail tente d'analyser la réponse d'une jet axisymétrique turbulent à une excitation fluidique stationnaire et instationnaire lorsque le contenu fréquentiel et aziumutal (!,m) de la perturbation est maîtrisé. Le dispositif de contrôle utilisé est composé de 16 microjets ronds répartis sur le bord de fuite de la tuyère. L'utilisation des microjets provoque une réduction du champ acoustique rayonné (particulièrement pour le cas de contrôle stationnaire). Le champ aérodynamique est ensuite sondé grâce à des mesures fil chaud et PIV stéréoscopique résolue en temps. L'excitation instationnaire permet d'utiliser les moyennes de phase afin d'effectuer une décomposition triple du champ de vitesse. L'étude de la composante cyclique de la “réponse du jet” montre une synchronisation spatio-temporelle importante sur une grande étendue spatiale. En d'autres mots, le forçage a une grande autorité déterministe sur l'écoulement. De plus, la comparaison de la composante cyclique de la réponse du jet avec la théorie de la stabilité linéaire indique qu'il existe des ondes d'instabilité hydrodynamique au sein du jet. L'analyse du jet contrôlé par injection fluidique stationnaire montre ensuite comment l'effet du contrôle peut être expliqué par la déformation du champ moyen conduisant à la réduction du taux de croissance des ondes d'instabilité dans le jet. Cette déformation est dûe à l'introduction d'un couple de paramètre (nombre d'onde/fréquences) pour lequel le champ moyen de l'écoulement est stable. La réponse du jet étant turbulente, cela implique que les tensions de Reynolds déforment le champ moyen de manière à ce que les modes les plus instables aient des taux de croissance plus faibles. / This work investigates the response of an axisymetric turbulent jet to steady and unsteady fluidic florcing where the azimuthal wavenumber-frequency (!,m) content of the perturbation is well known. The control setup is composed of 16 round microjets azimutally distributed around the nozzle lip. Such actuation can lead to a decrease in the acoustic energy radiated by the jet (especially for the steady case). The aerodynamic fied is investigated using hotwire measurements and time-resolved stereoscopic PIV. Using the unsteady forcing, phase-averaging is possible, and this allows the implementation of a triple decomposition of the measurements. Examination of the cyclic component of the flow response shows that a non-negligible phase-locked fluctuation is obtained over a large spatial extent, in other words, the actuation has good deterministic control authority over the flow. Furthermore, comparison of the cyclic component of the flow response with Linear Stability Theory supports the idea that the jet response comprises linear hydrodynamic instability waves. Subsequent analysis of jets controlled by steady fluidic actuation shows how the control effect can be explained by a mean-flow modification that leads to the reduction of instability-wave growth rates ; the mean flow modification is argued to be due to the introduction of azimuthal wavenumber-frequency pairs to which the mean flow is stable. The response is therefore turbulent, and involves Reynolds stresses which deform the mean-field such that the most unstable modes have lower growth rates.