Au cours de ces dernières années les processeurs sont devenus de plus en plus complexes (plusieurs niveaux de cache, vectorisation,...), l’augmentation de la complexité fait que l’étude des performances et les optimisations sont eux aussi devenus de plus en plus complexes et difficiles à comprendre. Donc développer un outil de caractérisation simple et facile d’utilisation des performances d’applications, serait de grande valeur. Le Modèle Roofline [17] promet un début de réponse à ces critères, mais reste insuffisant pour une caractérisation robuste et détaillée. Dans la première partie de cette thèse, Nous allons développer plusieurs versions améliorées du Roofline, robustes et précises, en passant par une version du Roofline en fonction du temps, des blocs et enfin la nouvelle version du Roofline introduite dans la suite de caractérisation Vtune d’Intel. Pour valider ces modèles, nous utilisons le benchmark LINPACK, STREAM ainsi qu’une mini-application développée au cours de cette thèse, qui résout l’équation de l’advection et qui servira de prototype pour l’évaluation de codes hydrodynamiques explicites. Nous portons aussi cette mini-application sur les co-processeurs d’Intel Xeon Phi KNL et KNC. Dans la deuxième partie de cette thèse nous nous intéressons à la simulation d’impact de vagues, à l’aide de codes industriels compressibles et incompressibles. Nous rajoutons plusieurs fonctionnalités dans le code compressible FluxIC, nous effectuons un chaînage de codes incompressible et compressible et enfin nous introduisons un nouveau schéma numérique appelé liquide incompressible et gaz quasi-compressible, qui permet de réaliser une simulation d’impact d’une vague via un code incompressible avec une correction compressible dans les zones où la compressibilité du gaz est importante. / During recent years computer processors have become increasingly complex (multiple levels of cache, vectorization, etc), meaning that the study of performance and optimization is also becoming more complex and difficult to understand. So a simple and easy-to-use model aimed at studying the performance of applications would be of great value. The Roofline model [17] promises to meet this criteria, but it is insufficient for robust and detailed characterization.In the first part of this thesis, several improved versions of the Roofline model, that are more robust and accurate, are developed by going through theRoofline version as a function of time and block, and finally a new Rooflinemodel is implemented in the Intel Vtune characterization suite. To validate thenew models, the LINPACK andtextitSTREAM benchmarks are used, as wellas, a mini-application developed during this thesis that solves the advectionequation and serves as a prototype for the evaluation of explicit hydrodynamicsimulation codes. This mini-application is also ported to the new Intel XeonPhi KNL and KNC co-processors.Simulation of wave impact using compressible and incompressible industrialcodes is the focus of the second part of this thesis. Several functionalities are added to the compressible FluxIC code, and a chaining of compressible andincompressible codes is carried out. Finally, a new numerical scheme called"incompressible liquid and quasi-compressible gas" is introduced, which allowsthe simulation of wave impact using an incompressible code with a compressiblecorrection in areas where gas compressibility is significant.

Because little was known about how the masonry lighthouses constructed during the 19th century at exposed locations around the British Isles were responding to wave action, the dynamic response of the Eddystone lighthouse under wave impacts was investigated. Like other so called 'rock lighthouses', the Eddystone lighthouse was built on top of a steep reef at a site that is fully submerged at most states of the tide. Consequently, the structure is exposed to loading by unbroken, breaking and broken waves. When the breaking occurs, wave loading leads to complex phenomena that cannot be described theoretically due to the unknown mixture of air and water involved during the wave-structure interaction. In addition, breaking waves are generally distinguished from unbroken and broken wave due to the fact that they cause impulsive loads. As a consequence, the load effects on the structural response require a dynamic analysis. In this investigation the dynamic response of the Eddystone lighthouse is investigated both in the field and by means of a small-scale model mounted in a laboratory wave channel. In particular, field data obtained by the use of geophones, cameras and a wave buoy are presented together with wave loading information obtained during the laboratory tests under controlled conditions. More than 3000 structural events were recorded during the exceptional sequence of winter storms that hit the South-West of England in 2013/2014. The geophone signals, which provide the structural response in terms of velocity data, are differentiated and integrated in order to obtain accelerations and displacements respectively. Dynamic responses show different behaviours and higher structural frequencies, which are related to more impulsive loads, tend to exhibit a predominant sharp peak in velocity time histories. As a consequence, the structural responses have been classified into four types depending on differences of ratio peaks in the time histories and spectra. Field video images indicate that higher structural frequencies are usually associated with loads caused by plunging waves that break on or just in front of the structure. However, higher structural velocities and accelerations do not necessarily lead to the largest displacements of around a tenth of mm. Thus, while the impulsive nature of the structural response depends on the type of wave impact, the magnitude of the structural deflections is strongly affected by both elevation of the wave force on the structure and impact duration, as suggested by structural numerical simulations and laboratory tests respectively. The latter demonstrate how the limited water depth strongly affects the wave loading. In particular, only small plunging waves are able to break on or near the structure and larger waves that break further away can impose a greater overall impulse due to the longer duration of the load. As a consequence of the depth limited conditions, broken waves can generate significant deflections in the case of the Eddystone lighthouse. However, maximum accelerations of about 0.1g are related to larger plunging waves that are still able to hit the lighthouse with a plunging jet. When compared to the Iribarren number, the dimensionless irregular momentum flux proposed by Hughes is found to be a better indicator concerning the occurrence of the structural response types. This is explained by the fact that the Iribarren number does not to take into account the effects of the wide tidal range at the Eddystone reef, which has a strong influence on the location of the breaking point with respect to the lighthouse. Finally, maximum run up were not able to rise up to the top of the lighthouse model during the laboratory tests, despite this having been observed in the field. As a consequence, the particular configuration of the Eddystone reef and the wind could have a considerable bearing and exceptional values of the run up, greater than 40 m, cannot be excluded in the field.