The aim of this master thesis is to explain using of the pressure-time method, commonly known as Gibson’s method for non-stationary discharge evaluation through water machineries. The thesis included the principle of this method, deriving the method and the problems, which happened in thanks of using this method. In the second part of this thesis are in details shown results of non-stationary discharge by pressure-time method and also there is the computation of the kinetic member on the resulting discharge. Next part is about refinement of this method by evaluation Penstock factor for each segment of feeder (direct pipe, taper and pipe elbow) using MS Excel and CFD calculations. The last capture is about influence of unsteady friction. In the beginning are shown basic terms and explain the principle of this losses. In the next part is proposed numerical model of losses and their influence on calculation of total Penstock factor of feeder.

Airplane wings, turbine blades and other structures subjected to air or water flows, can undergo motions depending on their flexibility. As such, the performance of these systems depends strongly on their geometry and material properties. Of particular importance is the contribution of different nonlinear aspects. These aspects can be of two types: aerodynamic and structural. Examples of aerodynamic aspects include but are not lomited to flow separation and wake effects. Examples of structural aspects include but not limited to large deformations (geometric nonlinearities), concentrated masses or elements (inertial nonlinearities) and freeplay. In some systems, and depending on the parameters, the nonlinearities can cause multiple solutions. Determining the effects of nonlinearities of an aeroelastic system on its response is crucial. In this dissertation, different aeroelastic configurations where nonlinear aspects may have significant effects on their performance are considered. These configurations include: the effects of the wake on the flutter speed of a wing placed under different angles of attack, the impacts of the wing rotation as well as the aerodynamic and structural nonlinearities on the flutter speed of a rotating blade, and the effects of the recently proposed nonlinear energy sink on the flutter and ensuing limit cycle oscillations of airfoils and wings. For the modeling and analysis of these systems, we use models with different levels of fidelity as required to achieve the stated goals. We also use nonlinear dynamic analysis tools such as the normal form to determine specific effects of nonlinearities on the type of instability. / Ph. D.

Two-dimensional flow in a viscous incompressible fluid, generated by a circular cylinder executing large-amplitude rectilinear oscillations in a plane perpendicular to its axis and parallel to one of the sides of a surrounding rectangular box filled with incompressible fluid is studied numerically. The circular cylinder moves back and forth through its own wake, resulting in an extremely complex flow field. For ease of implementing boundary conditions, a numerically generated body-fitted coordinate system is used. At each time step, the physical domain is doubly-connected, and a cut is introduced in order to map it into a rectangular computational domain. A body-fitted grid is generated by solving a pair of Laplace equations with a simple grid spacing control method which preserves the essential one-to-one property of the mapping. A finite difference/pseudo-spectral technique is used in this work to solve the Navier-Stokes equations in velocity-vorticity formulation. The time integration of the vorticity transport equation is handled by a fully explicit three-level Adams-Bashforth method. The two Poisson equations for the velocity components are 11-banded and block-diagonal in form, and are solved by a preconditioned biconjugate gradient routine. An integral constraint on the vorticity field is used to determine the boundary vorticity that simultaneously satisfies the no-slip and no-penetration conditions. The surface vorticity is uniquely determined by a general solution procedure developed in this study which is valid for flows over multiple solid bodies. With this approach, the physical process of vorticity generation on the solid boundary is properly simulated and the principle of vorticity conservation is satisfied. Results for various test cases and the complex vortex shedding phenomena generated by an oscillating circular cylinder are presented and discussed.

Hot-wire measurements taken in the turbulent wake of a flat plate are presented. Symmetrical and antisymmetrical perturbations at various amplitudes and frequencies were introduced into the wake by small flap oscillations. As predicted by linear stability theory, the sinuous (antisymmetric) mode was observed to be more significant than the varicose (symmetric) mode. When the amplitude of the perturbation was low, the spatial development of the introduced coherent perturbation was predicted well by linear stability theory. At high forcing levels, the wake spreading showed dramatic deviations from the well known square-root behavior of the unforced case. Measured coherent Reynolds stresses changed sign in the neighborhood of the neutral point of the perturbation, as predicted by the linear theory. However, the linear theory failed to predict the disturbance amplitude and transverse shapes close to the neutral point. Some nonlinear aspects of the evolution of instabilities in the wake are discussed. Theoretical predictions of the mean flow distortion and the generation of the first harmonic are compared to experimental measurements. Given the unforced flow and the amplitude of the fundamental wave, the mean flow distortion and the amplitude of the first harmonic are predicted remarkably well.

Numerical model for simulating sediment transport in unsteady flow is incomplete in several aspects: first of all, the numerical schemes have been proved suitable for the simulation of flow over rigid bed needs to be reevaluated for unsteady flow over mobile bed; secondly, existing non-equilibrium sediment transport models are empirically developed and therefore lack of consistency regarding the evaluation of the non-equilibrium parameters; thirdly, the sediment transport in various applications have unique features which needs to be considered in the models. Sediment transport in unsteady flows was studied using analytical and numerical methods. A one dimensional (1D) finite volume method (FVM) model was developed. Five popular numerical schemes were implemented into the model and their performances were evaluated under highly unsteady flow condition. A novel physically-based non-equilibrium sediment transport model was established to describe the non-equilibrium sediment transport process. Infiltration effects on flow and sediment transport was included to make the model applicable to simulate irrigation induced soil erosion in furrows. The Laursen (1958) formula was adopted and modified to calculate the erodibility of fine-grain sized soil, and then verified by laboratory and field datasets. The numerical model was applied to a series of simulations of sediment transport in highly unsteady flow including the dam break erosional flow, flash flood in natural rivers and irrigation flows and proved to be applicable in various applications. The first order schemes were able to produce smooth and reasonably accurate results, and spurious oscillations were observed in the simulated results produced by second order schemes. The proposed non-equilibrium sediment transport model yielded better results than several other models in the literatures. The modified Laursen (1958) formula adopted was applicable in calculating the erodibility of the soil in irrigation. Additionally, it was indicated that the effect of the jet erosion and the structural failure of the discontinuous bed topography cannot be properly accounted for due to the limitation of 1D model. The comparison between the simulated and measured sediment discharge hydrographs indicated a potential process associated to the transport of the fine-grain sized soil in the irrigation furrows.

A wind tunnel based investigation into the effects of unsteady yaw angles on the aerodynamics of a simple automotive body has been carried out to increase the understanding of the effects of unsteady onset conditions similar to those experienced in normal driving conditions. Detailed flow field measurements have been made using surface pressure tappings and PIV around a simple automotive model in steady state conditions and these have been compared to measurements made whilst the model was oscillating in the yaw plane. The oscillating motion was created by a motored crank which was used to produce consistent and repeated motion which produced a reduced frequency that indicated that a quasi-static response should be expected. The PIV data are used to compare the wake flow structures and the surface pressures are used to infer aerodynamic loads and investigate the development of the flow structures across the surfaces of the model. This includes a comprehensive comparison of the surface pressures on the sides of the model during a transient and quasi-static yaw angel oscillation. These results show differences between the two test conditions with the oscillating model results containing hysteresis and the greatest differences in the flow field occurring on the leeside of the model. Two configurations of the same model with different rear pillar geometries were used to isolate model specific effects. Square rear pillars create strong and stable trailing vortices which are less affected by the model motion whereas radiused rear pillars created weaker and less steady vortices that mixed with the quasi-2D wake behind the model base and were affected to a greater extent by the model motion. The unsteadiness in the trailing vortex separation feeds upstream into the A-pillar vortex demonstrating that small geometry changes at the rear can affect the entire flow field around the model.

The performance of an MBR under chemical shock loading conditions was investigated, to ascertain the robustness of the treatment system for urban water reuse. 32 household products and industrial substances, likely to be found in urban wastewater were assessed for toxicity, using Microtox and respirometry to obtain EC50 values. Six of these toxins were dosed into bench scale porous pots to observe any detrimental effects on the treatment system, in terms of effluent quality and potential foulant release. Four toxins were dosed into a pilot scale MBR to observe the effects of scale and enhanced biomass retention on the perturbations seen at bench scale. Mitigation of the foulants observed was investigated by the addition of ancillary chemicals. 10 household products and 6 industrial products were identified as being of risk to a biological treatment system with EC50 concentrations of the order that could be present in urban wastewater. 2 of the 6 toxins dosed into the porous pots caused a serious impact on the system reducing COD removal rates to 45%, compared with 92% average for the control pots, and increasing SMP turbidity to 11 NTU. 1 of the 4 toxins dosed into the MBR caused an impact, although less than observed in the porous pots, with the COD removal rate reducing to 77% and SMP turbidity increasing to a maximum of 9 NTU. Jar tests carried out to investigate mitigation potential of SMP turbidity found the cationic polymers MPE50 and high molecular weight polyDADMAC most efficient with reductions of SMP turbidity to <1 NTU possible although the toxins increased the dose necessary to achieve this.

La thèse traite de la simulation numérique de jets d’air lobés pour l’optimisation des Unités Terminales de Diffusion de l’Air pour le bâtiment. Il est présenté tout d’abord une analyse bibliographique exhaustive sur les jets d’air et sur les moyens passifs de leur contrôle. Vient ensuite un exposé des principes de la modélisation des écoulements turbulents. Sur la base des précédents éléments, nous abordons la phase de simulation et d’analyse de jets d’air lobés en trois parties. La première partie traite de la simulation d’un jet d’air libre à très faible nombre de Reynolds (Reynolds 800) en régime instationnaire. Dans cette étude, nous avons présenté plusieurs cas tests de simulation d’un jet d’orifice en forme de croix que nous avons confrontés à des résultats expérimentaux. Du point de vue quantitatif, la simulation du quart du jet a permis d’obtenir des caractéristiques globales assez satisfaisantes. Pour détecter d’une façon significative l’instationnarité du jet, il a été nécessaire de simuler la totalité du jet, mais ceci a été fait au détriment du nombre de mailles dans le domaine de calcul, ce qui conduit par conséquent à des résultats quantitativement inappropriés. La deuxième partie simule le même jet d’air mais en régime turbulent (Reynolds 3000). Sept modèles de turbulence ont été confrontés à des résultats expérimentaux. Nous montrons la pertinence du modèle RSM (Reynolds Stress Model) pour la prédiction de l’écoulement. La dernière partie est dédiée à la simulation de jets d’air turbulents en interaction. Cette partie se décline en trois études successives et complémentaires. La première a pour objet de rechercher le modèle de turbulence le plus pertinent capable de reproduire les phénomènes et les grandeurs utiles à l’application visée. La conclusion est qu’aucun des modèles de turbulence évalués n’est capable de prédire l’ensemble des caractéristiques dynamiques de l’écoulement de jets lobés en interaction. Cependant, parmi ces modèles, SST apparait nettement supérieur dans la prédiction de l’interaction des jets, de l’expansion dynamique globale et de l’entrainement de l’air ambiant lorsque l’écoulement est résolu à travers le diffuseur lobé. Sur la base des grandeurs dynamiques pertinentes identifiées et dont la prédiction par le modèle SST est jugée satisfaisante, nous entreprenons dans la suite une analyse de l’influence de la géométrie du lobe sur la capacité d’induction de l’écoulement. Un lobe de forme arrondie est alors trouvé plus avantageux qu’un lobe à angles droits. Enfin, la dernière étude s’intéresse à l’effet de la disposition et de l’espacement des orifices lobés sur les grandeurs globales de l’écoulement. Une solution géométrique permettant l’augmentation de la transparence de l’Unité Terminale de Diffusion de l’Air lobée est alors proposée. Elle devra être testée expérimentalement en conditions réelles, dans la cellule test échelle 1 thermiquement gardée nouvellement construite au LEPTIAB. / The thesis deals with the numerical simulation of lobed air jets for the optimization of Air Diffusion Terminal Units for buildings. First is presented a comprehensive literature review of the air jets and of the passive means of flow control. The manuscript continues with the principles of modeling of turbulent flows. Based on the previous considerations, we discuss the simulation and analysis of the air lobed jets following three parts. The first part deals with the simulation of an air jet at very low Reynolds number (Reynolds 800) in the unsteady regime. In this study, we presented several test cases of simulation for a cross-shaped orifice jet that we have confronted with experimental results. From the quantitative point of view, the simulation of a quarter of the jet’s section has yielded reasonably good results for the global characteristics of the flow. In order to detect in a significant way the unsteadiness of the jet, it was necessary to simulate the entire jet, but this was done at the expense of the number of cells in the computational domain, which consequently leaded to inappropriate quantitative results. In the second part we simulated the same air flow but in the turbulent regime (Reynolds 3000). Seven turbulence models have been confronted with experimental results. We show the relevance of the RSM turbulence model (Reynolds Stress Model) for predicting the flow.The last part is dedicated to the simulation of turbulent air jet in interaction. This part is divided into three successive and complementary studies. The first one was dedicated to find which turbulence model can reproduce most relevant phenomena and variables to the concerned application. The conclusion is that none of the turbulence models was able to predict all the dynamic features of the lobed jet flows in interaction. However, of these models, SST appears to be significantly better for the prediction of the interaction of the jets, the global dynamical expansion and the entrainment of the ambient air when the flow is numerically resolved through the lobed diffuser. On the basis of relevant dynamic quantities well predicted by the SST turbulence model, we undertake in the following part an analysis of the influence of the geometry of the lobe on the ability of the flow to entrain. A rounded lobe is then found to be more advantageous than a lobe with right angles. The final study examines the effect of the arrangement and spacing of the lobed orifices on the global quantities of the flow. A geometric solution allowing to increase the transparency of the lobed Air Diffusion Terminal Unit is then proposed. This solution should be tested experimentally in real conditions, in the new full scale model room constructed at LEPTIAB.

Alterations along the Mississippi River, such as dams and levees, have greatly reduced the amount of freshwater and sediment that reaches the Louisiana coastal area. Several freshwater and sediment diversions have been proposed to combat the associated land loss problem. To aid in this restoration effort a 1-D numerical model was calibrated, validated, and used to predict the response of the river to certain stimuli, such as proposed diversions, channel closures, channel modifications, and relative sea level rise. This study utilized HEC-RAS 4.0, a 1-D mobile-bed numerical model, which was calibrated using a discharge hydrograph at Tarbert Landing and a stage hydrograph at the Gulf of Mexico, to calculate the hydrodynamics of the river. The model showed that RSLR will decrease the capacity of the Lower Mississippi River to carry bed material. The stage at Carrollton Gage is not significantly impacted by large scale diversions

La réduction de l’impact environnemental est aujourd’hui l’un des défis cruciaux de l’industrie aéronautique. La poursuite d’une moindre consommation des aéronefs a conduit à concevoir des systèmes propulsifs en géneral, et des étages de compression en particulier, toujours plus compacts et chargés. Cette tendance dans la conception des moteurs est directement responsable de l’accentuation du caractère instationnaire des écoulements internes ainsi que de la favorisation dans l’émergence de phénomènes entrainant la perte de stabilité. L’étude expérimentale, conduite pendant ce projet de thèse, porte sur la caractérisation des écoulements dans un étage de compresseur axial en phase émergente et stabilisée du décrochage tournant, grâce à des mesures instationnaires de pression pariétale et de vitesse. L’étude doit son originalité à l’utilisation et au développement de techniques de post-traitement non-standard. La transformée par ondelettes se révèle être un outil particulièrement intéressant à la détection de structures cohérentes de brève durée, telles que le précurseur de type « spike » ainsi que les caractéristiques instantanées d’une cellule de décrochage tournant. A côté de cette approche d’analyse d’un signal localisé, différentes procédures de calcul de champs en moyenne de phase ont été mises au point, chacune adaptée aux spécificités du phénomène étudié et de la procédure expérimentale suivie. Il a été ainsi possible de suivre l’évolution des caractéristiques du champ de pression du régime nominal jusqu’à l’installation du décrochage tournant. L’alignement de la trajectoire du tourbillon de jeu avec la section d’entrée du rotor est associé au déclenchement du décrochage par précurseur de type « spike ». La comparaison entre les champs en phase transitoire et en décrochage établi, amène à affirmer que le précurseur n’est que le stade embryonnaire d’évolution du phénomène du décrochage. L’approche a, en outre, permis d’apprécier la complexité de la structure « interne » de la cellule qui apparait comme la succession d’une phase de propagation de décollement, une zone fortement débitante à charge presque nulle et une phase de ré-attachement de l’écoulement. / The reduction of the environmental impact is nowadays one of the crucial challenges of the aeronautic industry. The quest to lower the consumption of aircrafts has led to more compact and higher loaded engines in general, and especially compressor stages. This leads an increase of the internal flow unsteadiness and to the occurrence of unstable phenomena. The experimental study, performed during this work, concerns the characterization of flows in an axial compressor stage during both the emergence of rotating stall and its stabilized phase, by means of unsteady pressure and velocity measurements. The originality of the work proposed resides in the use and the development of non-standard data processing methods. The wavelets transform reveals to be an interesting tool for the detection of short coherent structures, like the spike-type precursor as well as the instantaneous features of a rotating stall cell. Beside this local approach, different procedures for phase-locked field measurements were developed, according to the specification of each studied phenomenon and the experimental proceedings. Thanks to these methods, it was possible to highlight the pressure field evolution until the development of the rotating stall regime. The alignment of the tip leakage vortex with the rotor inlet section forecasts a spike type stall onset. The comparison between transitional phase and fully developed stall fields conducts to assert that the precursor represent only the embryonic stage of the rotating stall evolution. This approach led to appreciate the complexity of the internal structure of the cell that appears to be the succession of stall propagation phase, zero-loaded high flow rate region and reattachment phase