The hydrodynamic properties of a horizontal cylinder which is free to pitch about an off-centred axis are studied and used to derive the equations of motion of a wave energy converter which extracts energy from incoming sea waves with a linear power-take-off mechanism. The present work follows from a recent study which compared the performance of an off-centred cylinder with those of the Edinburgh Duck wave energy converter. The small decrease in performance found is offset by a reduction in the likely costs associated with the manufacturing of the cylindrical cam compared with those of the asymmetric profile. As part of the survivability strategy in very energetic seas-states it had been planned to completely submerge the device so as to reduce the mooring forces. However, experiments with scale models show that a good absorption capacity is retained even when fully-submerged. The hydrodynamic properties of a horizontal cylinder that pierces the free-surface and of one that is fully submerged are therefore of central concern in this study. These properties are well known for the case of very long cylinders but they are now found for cylinders with different widths, drafts, submergence levels and water-depths. The hydrodynamic forces and moments at the off-centred axis are, furthermore, derived through the application of transformation formulae. The equation of motion of the off-centred cylinder is derived for one degree of freedom and its performance as a wave energy converter is analysed. A relationship which relates the resonance of the device with the location of the off-centred axis and its mass distribution is derived and used to optimize the design for average sea conditions attained at a real location. Design cases associated with three diameters of the cylinder are looked into detail for both a fully-submerged and free-surface piercing cylinder. The one degree of freedom model is extended to include a multi-body which has three degrees of freedom in order to describe the dynamics of a proposed wave powered desalination system based on a cylindrical Duck device. This mathematical model is derived through linearised Lagrangian equations of motion in which the hydrodynamic forces are included as generalised external forces. The advantage of such approach is to reduce the number of equations associated with multi-body systems by removing the reaction forces of holomonic constraints from the system of equations to solve. This model is validated through experiments with a scale model performed in the curved tank of the University of Edinburgh with both regular waves and mixed seas.

The diverse applications of advanced marine craft ascribed to their high speed and technological advancements has led to the use of stronger and lighter metals in such crafts. High speed, in effect also increases slamming loads as higher speed increases frequency of wave encounter while operating in waves. The present study is limited to wedge impact models. Fundamentally, the study is thus about two-dimensional (2D) wedge impact in water. In an attempt to predict the structural response to impact hydrodynamic force, a beam element based finite element (FE) computer program is written and the results of the code are presented in the thesis. A computational tool is developed to predict the transient elastic response of a 2D wedge under impact force using two different numerical methods. Both explicit and implicit numerical schemes have also been studied in order to apply to the present work. Explicit forth order Runge-Kutta (RK4) method and implicit Newmark-b (NB) method have been used in the present work. Coupling effects between excitation and response are ignored in the present numerical computations. Both the numerical schemes are validated using simple static solution and also modal expansion technique.

The spatial stability of hypersonic conical boundary layers is investigated utilizing different numerical techniques. First, the development and verification of a Linearized Compressible Navier-Stokes solver (LinCS) is presented, followed by an investigation of different effects that affect the stability of the flow in free-flight/ground tests, such as: high-enthalpy effects, wall-temperature ratio, and three-dimensionality (i.e. angle-of-attack). A temporally/spatially high-order of accuracy parallelized Linearized Compressible Navier-Stokes solver in disturbance formulation was developed, verified and employed in stability investigations. Herein, the solver was applied and verified against LST, PSE and DNS, for different hypersonic boundary-layer flows over several geometries (e.g. flat plate - M=5.35 & 10; straight cone - M=5.32, 6 & 7.95; flared cone - M=6; straight cone at AoA = 6 deg - M=6). The stability of a high-enthalpy flow was investigated utilizing LST, LinCS and DNS of the experiments performed for a 5 deg sharp cone in the T5 tunnel at Caltech. The results from axisymmetric and 3D wave-packet investigations in the linear, weakly, and strongly nonlinear regimes using DNS are presented. High-order spectral analysis was employed in order to elucidate the presence of nonlinear couplings, and the fundamental breakdown of second mode waves was investigated using parametric studies. The three-dimensionality of the flow over the Purdue 7 deg sharp cone at M=6 and AoA =6 deg was also investigated. The development of the crossflow instability was investigated utilizing suction/blowing at the wall in the LinCS/DNS framework. Results show good agreement with previous computational investigations, and that the proper basic flow computation/formation of the vortices is very sensitive to grid resolution.

Fluid structure interactions in the presence of a free surface includes complex phenomena, such as slamming, air entrainment, transient loads, complex free surface profiles and turbulence. Hence, an appropriate and efficient numerical method is required to deal with these type of problems (efficient both in problem setup and numerical solution). Eulerian mesh-based methods can be used to solve different types of problems, however they have difficulties in problems involving moving boundaries and discontinuities (e.g. fluid structure interactions in the presence of a free surface). Smoothed Particle Hydrodynamics (SPH) is a mesh-less Lagrangian particle method, ideal for solving problems with large deformation and fragmentation such as complex free surface flows. The SPH method was originally invented to study astrophysical applications and requires modifications in order to be applied for hydrodynamic applications. Applying solid boundary conditions for hydrodynamic applications in SPH is a key difference to the original SPH developed for astrophysics. There are several methods available in literature to apply solid boundaries in SPH. In this research, an accurate solid boundary condition is used to calculate the pressure at the boundary particles based on the surrounding fluid particles. The two main methods to calculate the pressure in the SPH method are the weakly compressible SPH (WCSPH) and the incompressible SPH (ISPH) approaches. The WCSPH uses the equation of state while ISPH solves Poisson's equation to determine the pressure. In this dissertation, an explicit incompressible SPH (ISPH) method is used to study nonlinear free surface applications. In the explicit ISPH method, Poisson's equation is explicitly solved to calculate the pressure within a projection based algorithm. This method does not require solving a set of algebraic equations for pressure at each time step unlike the implicit method. Here, an accurate boundary condition along with an accurate source term for Poisson's equation is used within the explicit method. Also, the sub-particle turbulent calculation is applied to the explicit ISPH method (which handles large-scale turbulent structures implicitly) in order to calculate the flow field quantities and consequently forces on the device more accurately. The SPH method is typically computationally more expensive than Eulerian-based CFD methods. Therefore, parallelization methods are required to improve the performance of the method, especially for 3D simulations. In this dissertation, two novel parallel schemes are developed based on Open Multi Processing (OpenMP) and Message Passing Interface (MPI) standards. The explicit ISPH approach is an advantage for parallel computing but our proposed method could also be applied to the WCSPH or implicit ISPH. The proposed SPH model is used to simulate and analyze several nonlinear free surface problems. First, the proposed explicit ISPH method is used to simulate a transient wave overtopping on a horizontal deck. Second, a wave impacting on a scaled oscillating wave surge converter (OWSC) is simulated and studied. Third, the performance and accuracy of the code is tested for a dam-break impacting on tall and short structures. Forth, the hydrodynamic loads from the spar of a scaled self-reacting point absorber wave energy converter (WEC) design is studied. Finally, a comprehensive set of landslide generated waves are modeled and analyzed and a new technique is proposed to calculate the motion of a slide on an inclined ramp implicitly without using a prescribed motion. / Graduate

L'évolution sédimentaire des milieux lagunaires est un phénomène complexe faisant intervenir à la fois des processus intenses sur le court terme (crues, tempêtes) et des processus plus lents sur le long terme (variations du niveau marin moyen, changements climatiques). Si les mécanismes généraux de ces phénomènes sont bien connus, leur variabilité spatiale et temporelle les rends difficiles à estimer au niveau local. La grande diversité des milieux lagunaires et l'influence des actions anthropiques rendent plus hasardeuse encore cette estimation. Dans cette étude, je me suis intéressé au cas du système lagunaire méditerranéen des « étangs Palavasiens, étang de l'Or, canal du Rhône à Sète » situé dans le Golfe du Lion (Sud de la France). L'utilisation d'une approche pluridisciplinaire a permis d'évaluer la dynamique sédimentaire sur des échelles de temps multiples. Sur les deux derniers siècles, le comblement du système lagunaire a pu être estimé à la vitesse moyenne de 1,3 mm.an-1 à travers l'utilisation conjointe de données géographiques historiques et d'analyses géochronologiques (210Pb, 137Cs). Une perte de surface imputable pour moitié aux aménagements anthropiques est également mise en avant au cours du XXème siècle. Une campagne de mesures haute fréquence de la dynamique hydro-sédimentaire a été menée à court-terme (2 ans). Elle a permis de déterminer l'influence des conditions de forçages physiques sur les processus internes (érosion, remise en suspension, dépôt). Les seuils caractéristiques tels que la tension critique d'érosion ont pu être estimés et reliés aux conditions météorologiques. Le bilan net sur les stations suivies durant cette période montre une perte de sédiment. Ce bilan opposé aux estimations historiques sur les mêmes secteurs est probablement en lien avec les conditions d'apports réduites durant la période investiguée. L'adaptation d'un modèle numérique sur la zone d'étude a été entreprise afin de préciser cette dynamique sur une plus large échelle spatiale et temporelle. / The sedimentary evolution of coastal lagoons is a complex phenomenon involving both short term extreme processes (floods, storms) and long term processes (mean sea level variations, climate change). If general mechanisms of these phenomena are well known, their spatial and temporal variability makes them difficult to assess at the local scale. The diversity of lagoonal environments and human influence makes this even more risky. I have focussed this study on the case of a Mediterranean lagoon system : “Palavasian lagoons, Or lagoon, and Rhône-Sète waterway” which is located in the Gulf of Lion (South of France). A multidisciplinary approach was used to assess sediment dynamics on multiple time scales. An average filling rate of 1.3 mm.year-1 over the two last centuries was assessed using a both historical maps and geochronology (210Pb, 137Cs). An area loss due for half to anthropogenic impacts was also highlighted in the twentieth century. A short term (2 years) and high frequency monitoring of in situ hydro-sedimentary dynamics was performed to determine the influence of physical forcing over internal processes (erosion, resuspension, deposition). The main characteristics thresholds were estimated and related to weather conditions. The observed net balance during this monitoring shows a loss of sediment. This assessment, opposite of historical trends, is probably related to the conditions of reduced river contribution. The implementation of a numerical model is going on in order to explain the dynamics on a larger spatial and temporal scales.

L’objectif de cette thèse était la modélisation numérique de la torche à plasma à couplage inductive. (ICP). Nous avons établi les bases de données nécessaires : composition, propriétés thermodynamiques et de transport appliqués aux mélanges d’argon, d’acide nitrique et d’eau. Le modèle hydrodynamique de la torche ICP (7 spires) considère le plasma à l'équilibre thermodynamique et couple les équations de Navier-Stokes pour décrire l'écoulement du plasma aux équations de Maxwell pour décrire l'évolution du champ électrique et du champ magnétique. / The purpose of the work was the numerical modeling of the inductive coupling plasma torch. (ICP). We have established the necessary databases: composition, thermodynamic and transport properties applied to argon mixtures of nitric acid and water. The hydrodynamic model of the ICP torch (7 coils) considers the plasma at thermodynamic equilibrium and uses the Navier-Stokes equations to describe the plasma flow and the Maxwell equations to describe the evolution of the electric field and the magnetic field.

Water is a simple molecule but is an essential part of life. One key aspect of the properties of water is the hydrophobic effect, and whilst there is an appreciation of this phenomenon at the macro-scale (raindrops falling off leaves) and the micro-scale (the structure of cellular systems), a complete understanding at the molecular level still eludes science. Addressing this issue, our studies involve synthetic supramolecular compounds that assemble in water via the hydrophobic effect. First of all, a novel water-soluble deep-cavity cavitand was synthesized. It possesses four endo methyl groups on top rim of the cavitand, eight water-solubilizing carboxylic acid groups coated on the cavitand exterior, and a relatively large hydrophobic interior. Compared to a previous well-studied water-soluble deep-cavity cavitand octa-acid (OA), this novel cavitand (TEMOA) possesses a non-monotonic assembly profile in the presence of a homologous series of straight-chain alkanes. Three supramolecular species were observed: 1:1, 2:2, and 2:2 and they are approximately isoenergetic. Second, we examined the guest-controlled self-sorting in assemblies. A mixture of OA and TEMOA formed hetero-capsular complex driven by the hydrophobic effect. The extent of homo- or hetero-dimerization is intimately tied to the size of the guest being encapsulated. TEMOA is less predisposed to dimerize than OA, thus TEMOA possesses the ability to form various self-assembled states, such as tetrameric and hexameric assemblies. Furthermore, we also discussed our observation of how external stimuli such as changing the nature or concentration of a co-solute salt influences a unique, unusual transition from one assembled state to another.

The purpose of this research is to develop a 3-D numerical model on the Lower Mississippi River to simulate hydrodynamics and non-cohesive sediment transport. The study reach extends from Bonnet Carré Spillway (RM 127) to Head of Passes (RM 0). Delft3D with sigma coordinates was selected as the river modeling tool. This model River domain is characterized by a complex distributary system that connects the Mississippi River to the Gulf of Mexico. The boundary conditions were: water levels in the Gulf and Head of Passes; and discharges upstream. For the calibration, there are observed data for both types of boundary conditions. Several periods of high discharge were simulated to compare water level, discharge, velocity profiles and sediment transport with measurements and accomplish calibration and validation of the model. A calibrated 3-D model has been developed with the following %RMSE: 5% for stage; 6% for discharge; and 5% for sand load.

In all coating applications, a liquid film displaces air in contact with a dry solid substrate. At a low substrate speed a thin uniform wetting line is formed on the substrates surface, but at a high speed the wetting line becomes segmented and unsteady as air becomes entrained between the substrate and the liquid. These air bubbles affect the quality of the coated product and any means to postpone this at higher speeds without changing the specifications of the coating liquid is desirable. This research assesses the validity of a theoretically based concept developed by Blake and Rushack [1] and exploited by Cohu and Benkreira [2] for dip coating. The concept suggests that angling the wetting line by an angle ß would increase the speed at which air is entrained by a factor 1/cos ß. In practice, if achieved this is a significant increase that would result in more economical operation. This concept was tested in a fast coating operation that of curtain coating which is already enhanced by what is known as hydrodynamic assistance [2]. Here we are effectively checking an additional assistance to wetting. The work, performed on a purposed built curtain coater and a rotating die, with a range of fluids showed the concept to hold but provided the data are processed in a way that separate the effect of curtain impingement from the slanting of the wetting line.

O uso de agroquímicos pode causar uma grande variedade de impactos negativos em ambientes aquáticos. Em áreas de exploração agrícola, onde são usados tais produtos, há uma demanda por sistemas de bioremediação que conjuguem baixos custos e simplicidade operacional. Na presente tese são apresentados os resultados da pesquisa que consistiu em se investigar o destino ambiental do agroquímico ametrina quando adicionado a alagados construídos. Foram utilizados sistemas em micro e mesoescala, construídos em Viçosa-MG, que consistiam de macrófitas aquáticas (T. latifolia) plantadas sobre um leito de brita. Para melhor avaliação dos mecanismos nos alagados foi realizado um estudo hidrodinâmico e observou-se que as células operam com boa eficiência hidráulica. No experimento em mesoescala verificou-se a retenção/remoção de 39% da massa de ametrina aplicada, não sendo observadas diferenças significativas entre as 4 unidades utilizadas. No estudo em microcosmo, não foram observadas variações em relação ao teor de nutrientes e a morfo-anatomia das macrófitas. Tal fato pode ser interpretado positivamente, visto que mesmo sob perturbação ambiental a planta adulta conseguiu manter suas características. Como fator a ser considerado, verificou-se que o desenvolvimento inicial da T. latifolia pode ser prejudicado por reduzidas concentrações de ametrina. De uma maneira geral, observou-se que sistemas alagados construídos operando sob escoamento subsuperficial poderão vir a ser usados na mitigação da contaminação de águas por praguicidas. / Pesticides can cause a great spectrum of negative impacts in aquatic environmental. In agricultural lands, these products are largely used and in these regions there is a demand for low costs and simple bioremediation systems. In the present thesis, the results of the research about ametryn environmental fate in subsurface flow constructed wetlands systems are presented. The wetlands cells were built in microcosms and mesocosms scales at Viçosa city, Minas Gerais state. The experimental system was consisted of aquatic macrophytes (T. latifolia) cultivated on a porous gravel bed. A hydrodynamic study was performed for the better knowledge of the mechanisms of pesticide transport. The cells presented good hydraulic efficiency and in mesocosms wetlands were observed that 39% of ametryn amended was removed/retained. No statistical difference among the 4 cells performances was registered. At green house (microcosm) tests, no effects in nutrients and morpho-anatomy were observed. This fact can be interpreted positively, because ever under environmental disturbance, the macrophyte maintained its characteristics. However, aqueous 10-d germination and growth experiment indicate possible ametryn harmful effects to T. latifolia development. In general way, it was observed that vegetated constructed wetlands can be used in depollution of pesticides-contaminated waters.