Flow kinematics of green water due to plunging breaking waves interacting with a simplified, three-dimensional model structure was investigated in laboratory. Two breaking wave conditions were tested: one with waves impinging and breaking on the vertical wall of the model at the still water level and the other with waves impinging and breaking on the horizontal deck surface. The incoming wave parameters were selected similar to observed wave parameters for the maximum wave height for Hurricane Ivan based on Froude scaling. The Bubble Image Velocimetry (BIV) technique was used to measure the flow velocity. Measurements were taken on a vertical plane located at the center of the deck surface and a horizontal plane located slightly above the deck surface. The evolution of green water flow kinematics in time and space is revealed in the study. The unsteady and non-uniform velocities were found to be quite different between the two wave conditions, even though the incoming waves are nearly identical. It was observed that the maximum velocity appears near the green water wave front and is 1.44C with C being the wave phase speed for the deck impingement case and 1.24C for wall impingement case. The velocity variations in the present study were compared with that in an earlier study using a two-dimensional model with the same wave condition as in the wall impingement condition. It was found that the magnitudes of the maximum vertical velocity is very different between these two models (1.7C in the 3D model versus 2.9C in the 2D model), whereas the magnitudes of the maximum horizontal velocity on the deck are very similar (1.2C in both 3D and 2D models). The applicability of dam-break theory on green water velocity prediction for the three-dimensional model was also investigated. It was found that the dam-break theory works very well in terms of predicting the maximum velocity, which is also the front velocity, but not the spatial distribution of the velocity on the deck. Furthermore, pressure measurements were performed at two vertical planes: one at the centre and the other at 0.05 m away from the centre. Ensemble averaged pressure variations were compared. Two types of pressure variations, impulsive type and non-impulsive type were observed. Impact pressure was successfully related to the pressure rising time. Void fraction was measured for few locations near the model front edge. Predictions of maximum impact pressure based on the measured pressure and flow velocity were investigated linking pressure with kinetic energy. Constant impact coefficient of 1.3 was found for wall impingement wave. However, for deck impingement wave, it was not possible to find a constant impact coefficient. It was also found that there is a linear relationship between the rising pressure gradient and the impact coefficient.

L'étude porte sur l'impact de vagues sur une paroi rigide en deux dimensions. Les travaux de modélisation numérique ont été réalisés à partir du code JOSEPHINE, utilisant la méthode Smoothed Particle Hydrodynamics (SPH), développé au sein du laboratoire LOMC. La méthode choisie repose sur une approximation faiblement compressible des équations d'Euler. Dans un premier temps, l'étude d'un cas académique de l'impact d'un jet triangulaire a permis de valider et améliorer le schéma numérique permettant la modélisation d'impacts violents. Les pressions d'impacts ont été étudiées et comparées à d'autres résultats analytiques et numériques. Dans un second temps, l'impact d'une vague solitaire déferlante a été modélisé. Les pressions d'impact ont été déterminées et comparées avec celles issues d'expériences. Après une analyse numérique approfondie des simulations mono-phasiques, un modèle diphasique a été spécifiquement développé pour tenir compte à la fois des phases eau et air. Le modèle SPH diphasique a permis d'améliorer la qualité des résultats, notamment pour le cas « air pocket impact », où une poche d'air est emprisonnée lors de l'impact. Le but final de ce travail est d'étudier la survivabilité des récupérateurs d'énergie marine adossés à des structures côtières lors d'événements météorologiques violents. / The present manuscript focuses on the wave impact on a rigid wall in two dimensions. The numerical computations were performed using a Smoothed Particle Hydrodynamics (SPH) software named JOSEPHINE, developed at the LOMC laboratory. The software is based on a weakly-compressible SPH model, where Euler equation of motion is solved. Firstly, an academic test case, the impact of a triangular jet was used to validate and improve the numerical scheme to model violent impacts.The impact pressures were studied and compared to analytical and other numerical results. Secondly, the impact of a breaking solitary wave was modelled.The impact pressures were determined and compared with those obtained in the experiments. After a depth numerical analysis of mono-phase flow computations, a two-phase model was developed specifically to consider both water and air phases. The two-phase SPH model improved the results quality, especially for the case "air pocket impact", where an air pocket is trapped during the impact. The ultimate goal of this work is to study the survivability of coastal structures equipped with a marine energy recovery device during severe weather events.

The issue of descaling is an important part of the forging and heat treatment of steel and semi products of steel production. Rising of new information and study of this process can increase efficiency and improve the surface quality after descaling. This thesis is focused on the mechanisms of the high pressure hydraulic descaling qualification and study of the chemical compounds of which the scales grown. To achieve all goals of this work and to get a comprehensive view of descaling process, few experimental measurements and numerical analyses were performed. All experimental measurements were focused on obtaining data about fundamental parameters and effects of the hydraulic descaling. The data obtained from measurements were applied to numerical analyses, which aimed to discover a deeper relation and to confirm the experimental results. This thesis can be divided into two main parts. The first part is devoted to parameters of the water jet study. The main studied characteristics of the high pressure hydraulic water jet were heat transfer coefficient and impact pressure at different modes such as standard or pulsating water jet. Experimentally measured data of these parameters were applied in numerical analyses. The numerical analyses were focused on studying the impact of the water jet parameters on the stresses in the oxide scale layers. A further water jet analysis was focused on the influence of the individual parts of the hydraulic system (such as water chamber or stabilizer) on its characteristics. In this part different types of the water chambers in combination with different types of stabilizers on the impact pressure values were investigated. These measurements were supported by fluid flow analysis through the hydraulic system. The second part of this work was focused on getting mechanical properties of the oxide scales from specimens prepared from standard structural steel and specimens from silicon steel. In this thesis, the influence of various parameters and characteristics was studied on these two types of steel. Mechanical properties of oxide scale structures were carried out by the Small Punch Test method. To obtain the fundamental mechanical properties such as Young´s modulus, yield strength and ultimate strength, material parameters based on the measured data were optimized. The whole work was carried out in order to get valuable and comprehensive results about high pressure hydraulic descaling process and influencing factors as well as about oxide scales themselves.

The issue of descaling is an important part of the forging and heat treatment of steel and semi products of steel production. Rising of new information and study of this process can increase efficiency and improve the surface quality after descaling. This thesis is focused on the mechanisms of the high pressure hydraulic descaling qualification and study of the chemical compounds of which the scales grown. To achieve all goals of this work and to get a comprehensive view of descaling process, few experimental measurements and numerical analyses were performed. All experimental measurements were focused on obtaining data about fundamental parameters and effects of the hydraulic descaling. The data obtained from measurements were applied to numerical analyses, which aimed to discover a deeper relation and to confirm the experimental results. This thesis can be divided into two main parts. The first part is devoted to parameters of the water jet study. The main studied characteristics of the high pressure hydraulic water jet were heat transfer coefficient and impact pressure at different modes such as standard or pulsating water jet. Experimentally measured data of these parameters were applied in numerical analyses. The numerical analyses were focused on studying the impact of the water jet parameters on the stresses in the oxide scale layers. A further water jet analysis was focused on the influence of the individual parts of the hydraulic system (such as water chamber or stabilizer) on its characteristics. In this part different types of the water chambers in combination with different types of stabilizers on the impact pressure values were investigated. These measurements were supported by fluid flow analysis through the hydraulic system. The second part of this work was focused on getting mechanical properties of the oxide scales from specimens prepared from standard structural steel and specimens from silicon steel. In this thesis, the influence of various parameters and characteristics was studied on these two types of steel. Mechanical properties of oxide scale structures were carried out by the Small Punch Test method. To obtain the fundamental mechanical properties such as Young´s modulus, yield strength and ultimate strength, material parameters based on the measured data were optimized. The whole work was carried out in order to get valuable and comprehensive results about high pressure hydraulic descaling process and influencing factors as well as about oxide scales themselves.

The thesis summarizes general and up-to-date knowledge of descaling during the continuous production of the hot-rolled steel and proposes further streamlining of this process in industrial production. The first chapter of the thesis deals with the origin, structure and physical properties of the scales. The second chapter describes the principles of descaling by using a high pressure flat water jet. The third chapter introduces the principles of the experimental methods and describes the used laboratory equipment. The fourth chapter summarizes the description of the particular experiments and their evaluation, and thus represents the focus of the dissertation. It is divided into six sections which independently solve predefined objectives of the dissertation. The first section focuses on the height and structure development of the scales on 54SiCr6 and HDT580X steels. It has been proven that the height of the formed scales increases with the time and temperature of the oxidation. The layered nature of the scales was verified at the same time. The second section examines the effect of the nozzle stabilizer on the focussing and distribution of the impact pressure of the nozzle. Experiments have shown that increase of 11 % of an average maximum nozzle pressure can be achieved, depending on the type of nozzle and the length of the stabilizer. The third section deals with the analysis of shadowgraphy images of water jet structures of the nozzles. A script was developed for analysis of these shadowgraphy photos by an adaptive thresholding. The findings are correlated using a regression analysis with an average heat transfer coefficient. It has been reported that most of the standard nozzle configurations produced disintegrated stream of little droplets at the height of the rolled surface. The fourth section focuses on the area of water jet overlap, especially the area of the so-called washout, where the impact pressure of one nozzle is reduced by the nozzle stream of the other. The influence of the pressure change and the mutual displacement of the nozzles is investigated. The analysis showed that the change of pressure did not have any effect on the percentage of reduction of the impact pressure in the area of the washout. It has been shown that if the area of the washout is wide the descaling efficiency in this area may be reduced. The fifth section builds on the previous section and focuses directly on the areas of waterjet overlaps. The influence of the change of rotation and pitch of the nozzles is studied. Experiments have shown that small changes in nozzle pitch do not have a significant impact on impact pressure and heat transfer coefficient. The effect of nozzle rotation, on the other hand, was a significant factor for the efficiency and homogeneity of the descaling of the surface. The last section deals with the effect of the rolling speed on the heat transfer coefficient in the descaling process. The regression model has shown that with a higher rolling speed there is a reduction in the average heat transfer coefficient. Conclusion summarizes the results of the dissertation and proposes which findings can be used in the industry to make the descaling process more effective.

Ce travail de thèse porte sur les outils statistiques pour l'évaluation des maxima de charges de sloshing dans les cuves de méthaniers. Selon les caractéristiques du navire, son chargement et les conditions de navigation, un ballotement hydrodynamique est observé à l'intérieur des cuves, phénomène communément appelé sloshing. La détermination des charges qui s'appliquent à la structure est basée sur des mesures de pression d'impact au moyen d'essais sur maquette. Les maxima de pression par impact, extraits des mesures, sont étudiés. La durée d'un essai est équivalente à 5 heures au réel et insuffisante pour déterminer des maxima de pression associés à de grandes périodes de retour (40 ans). Un modèle probabiliste est nécessaire pour extrapoler les maxima de pression. Le modèle usuel est une loi de Weibull. Comme ce sont les valeurs extrêmes des échantillons qui nous intéressent, les ajustements sont aussi effectués par les lois des valeurs extrêmes et de Pareto généralisées via les méthodes de maximum par bloc et d'excès au-dessus d'un seuil.L'originalité du travail repose sur l'emploi d'un système alternatif, plus pertinent pour la capture des maxima de pression et d'une quantité de 480 heures de mesures disponible pour les mêmes conditions d'essai. Cela fournit une distribution de référence pour les maxima de pression et nous permet d'évaluer la pertinence des modèles sélectionnés. Nous insistons sur l'importance d'évaluer la qualité des ajustements par des tests statistiques et de quantifier les incertitudes sur les estimations obtenues. La méthodologie fournie a été implémentée dans un logiciel nommé Stat_R qui facilite la manipulation et le traitement des résultats. / This thesis focuses on statistical tools for the assessment of maxima sloshing loads in LNG tanks. According to ship features, tank cargo and sailing conditions, a sloshing phenomenon is observed inside LNG tanks. The determination of sloshing loads supported by the tank structure is derived from impact pressure measurements performed on a test rig. Pressure maxima per impact, extracted from test measurements, are investigated. Test duration is equivalent to 5 hours in full scale. This duration is not sufficient to determine pressure maxima associated with high return periods (40 years). It is necessary to use a probabilistic model in order to extrapolate pressure maxima. Usually, a Weibull model is used. As we focus on extreme values from samples, fittings are also performed with the generalized extreme value distribution and the generalized Pareto distribution using block maximum method and peaks over threshold method.The originality of this work is based on the use of an alternate measurement system which is more relevant than usual measurement system to get pressure maxima and a 480 hours measured data available for same test conditions. This provides a reference distribution for pressure maxima which is used to assess the relevance of the selected probabilistic models. Particular attention is paid to the assessment of fittings quality using statistical tests and to the quantification of uncertainties on estimated values.The provided methodology has been implemented in a software called Stat_R which makes the manipulation and the treatment of results easier.

This work is focussed on hydraulic descaling of hot surfaces. Hydraulic descaling is a process when layers of oxides are removed from hot steel surfaces during continuous rolling. High pressure water beam is used. Quality of descaled surfaces is important for final quality of rolled product. Insufficient descaling causes drop of final quality, degradation of rolls and lost of yields. High-pressure water beam has two effects on a scale layer. The first effect is mechanical caused by impact pressure. The second one is a relatively intensive thermal shock depending on a set of parameters (water pressure, nozzle type, distance from the surface, inclination angle, speed of product moving). There are a lot of theories about principles of scales removing. Main task of this work is to make it clear which theory is acceptable and which is just ,,theory”. For this purpose mathematical modelling and experimental work were used. In experimental part, three types of experimental measurement were done. First one, measurement of dynamical effect of water beam – impact pressure. Second one, measurement of temperature drop when a product is passing under the nozzle. Measured data (temperatures) from this measurement are evaluated with inverse task and heat transfer coefficient is obtained. And the third experimental measurement is simulation of whole process of descaling. Quality of descaled surfaces is valuated according to amount of remained oxide scales. Data from firs and second experimental measurement are used as boundary conditions for mathematical modelling. For mathematical simulations, FEM (finite element method) system ANSYS was used. Obtained data from experimental measurement were applied on 2D and 3D models of basic steel material with layer of scale. Influence of theses data on final temperature, stress and strain fields were observed.