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21	Vibrations hydroélastiques de réservoirs élastiques couplés à un fluide interne incompressible à surface libre autour d’un état précontraint / Hydroelastic vibrations of elastics tanks containing an incompressible free-surface fluide around a prestressed state Hoareau, Christophe 16 July 2019 (has links) Cette thèse de doctorat porte sur le calcul par la méthode des éléments finis du comportement dynamique de réservoirs élastiques précontraints contenant un liquide interne à surface libre. Nous considérons que la pression hydrostatique exercée par le fluide interne incompressible sur les parois flexibles du réservoir est à l’origine de grands déplacements, conduisant ainsi à un état d’équilibre non-linéaire géométrique. Le changement de raideur lié à cet état précontraint induit un décalage des fréquences de résonances du problème de vibrations linéaires couplées.L’objectif principal du travail est donc d’estimer, par des approches numériques précises et efficaces, l’influence des non-linéarités géométriques sur le comportement hydroélastique du système réservoir/liquide interne autour de différentes configurations d’équilibre. La méthodologie développée s’effectue en deux étapes. La première consiste à calculer l’état statique non-linéaire par une approche éléments finis lagrangienne totale. L’action du fluide sur la structure est ici modélisée par des forces suiveuses hydrostatiques. La deuxième étape porte sur le calcul des vibrations couplées linéarisées. Un modèle d’ordre réduit original est notamment proposé pour limiter les coûts de calcul associés à l’estimation de l’effet de masse ajoutée. Enfin, divers exemples sont proposés et comparés à des résultats de la littérature (issus de simulations numériques ou d’essais expérimentaux) pour montrer l’efficacité et la validité des différentes approches numériques développées dans ce travail. / This doctoral thesis focuses on the calculation by the finite element method of the dynamic behavior of prestressed elastic tanks containing an internal liquid with a free surface. We consider that the hydrostatic pressure exerted by the incompressible internal fluid on the flexible walls of the tank causes large displacements, thus leading to a geometric non-linear equilibrium state. The change of stiffness related to this prestressed state induces a shift in the resonance frequencies of the coupled linear vibration problem. The main objective of the work is therefore to estimate, through precise and efficient numerical approaches, the influence of geometric nonlinearities on the hydroelastic behavior of the reservoir/internal liquid system around different equilibrium configurations. The methodology developed is carried out in two stages. The first one consists in calculating the non-linear static state by a total Lagrangian finite element approach.The action of the fluid on the structure is modelled here by hydrostatic following forces. The second step is the calculation of linearized coupled vibrations. In particular, an original reduced order model is proposed to limit the calculation costs associated with the estimation of the added mass effect. Finally, various examples are proposed and compared with results from the literature (from numerical simulations or experimental tests) to show the effectiveness and validity of the different numerical approaches developed in this work. Hydroélasticité Interaction fluide-Structure Non-Linéarité géométrique Méthode des éléments-finis Ligne de niveau Projection sur base réduite Forces suiveuses hydrostatiques Précontrainte Masse ajoutée Modèle d’ordre réduit Hydroelasticity Fluid-structure Interaction Geometrically non linear Geometrical non-Linearity Level-Set Finite element method Hydrostatic follower forces Prestressing Added mass Reduced order model 620.106 624.17
22	New modelling and simulation methods to support clean marine propulsion Grant, Michael 24 August 2021 (has links) The marine industry has increased its adoption of pure-electric, diesel-electric, and other non-traditional propulsion architectures to reduce ship emissions and fuel consumption. While these technologies can improve performance, the design of a propulsion system becomes challenging, given that no single technology is superior across all vessel types. Furthermore, even identical ships with different operating patterns may be better suited to different propulsion technologies. Addressing this problem, previous research has shown that if key elements of a vessel's operational pro file are known, simulation and optimization techniques can be employed to evaluate multiple propulsion architectures and result in a better propulsion system design and energy management strategy for a given vessel. While these studies have demonstrated the performance improvements that can be achieved from optimizing clean marine propulsion systems, they rely on vessel operational profiles obtained through physical measurement from existing ships. From a practical point of view, the optimization of a vessel's propulsion system needs to occur prior to a vessel's construction and thus precludes physical measurement. To this end, this thesis introduces a marine simulation platform for producing vessel operational profiles which enable propulsion system optimization during the ship design process. Core subsystem modules are constructed for simulating ship motions in 3 degrees of freedom and result in operational profile time-series, including propulsion power. Data is acquired from a benchmark vessel to validate the simulation. Results show the proposed approach strikes a balance between speed, accuracy, and complexity compared with other available tools. / Graduate model-based design MBD hybrid marine propulsion optimization simulation ship vessel DOF motion propeller torque thrust diesel-electric all-electric EV FES BES PHES HES ESS energy automation autonomous resistance hull ocean current added mass platform CFD hybrid electric batteries ultra capacitors emissions fuel consumption LNG motor engine energy management strategy control power energy wind waves strain coefficient hydrodynamic derivative MMG Maneuvering Modeling Group manoeuvring ferry design electric diesel azimuth thruster podded fouling roughness autopilot
23	Partikelmodellierung der Strukturbildung akustischer Kavitationsblasen in Wechselwirkung mit dem Schalldruckfeld / Particle modeling of acoustic cavitation bubble structure formation and interaction with the acoustic pressure field Koch, Philipp 29 August 2006 (has links) No description available. 530 Physik Mathematics and Computer Science akustische Kavitation Strukturbildung akustische Lichtenbergfigur nichtlineare radiale Blasendynamik Keller-Miksis-Modell Oberflächenstabilität Gasdiffusion Partikelmodellierung primäre und sekundäre Bjerkneskraft Reibungskraft virtuelle Masse Ultraschallfeld Helmholtz-Gleichung stehende Schallfeldmode Resonanzverschiebung Blasen-Flüssigkeits-Gemisch van Wijngaarden-Wellengleichung Einzelblase Vielblasensysteme Hochgeschwindigkeitsaufnahme acoustic cavitation structure formation acoustic Lichtenberg figur nonlinear radial bubble oscillation Keller-Miksis model surface stability gas diffusion particel modeling primary and sekundary Bjerknes force drag force added mass ultrasonic field Helmholtz equation standing wave field resonance shift bubble liquid mixture van Wijngaarden wave equation single bubble multi bubble systems high-speed video observations 33.12 30.20 RHK 000: Ultraschall {Physik: Akustik} RHH 150: Schallausbreitung -reflexion in Flüssigkeiten {Physik: Akustik}

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