Orientador: Carlos Roberto Minussi / Co-orientador: Geraldo De Freitas Maciel / Banca: Anna Diva Plasencia Lotufo / Banca: Mara Lúcia Martins Lopes / Banca: Luís Miguel Chagas da Costa Gil / Resumo: O escorregamento de massas sólidas em lagos de águas tranquilas geram ondas devido à transferência de energia da massa deslizante para o corpo d'água. Essas ondas, chamadas de ondas de submersão, em particular as ondas solitárias, são conhecidas e estudadas há vários anos principalmente pela capacidade energética deste tipo de onda e seu potencial danoso. Entretanto, aproximações analíticas do fenômeno em tela esbarram em diversas dificuldades. Em outras palavras, a fase de geração de ondas, notadamente das ondas de impacto, é sabidamente complexa, não apenas pela dificuldade no estabelecimento da superfície livre (região do splash), mas também pelo relacionamento da dinâmica do material impactante com a altura da onda resultante. Por esse motivo, técnicas numéricas vêm sendo empregadas nestes fenômenos. Entre as aproximações numéricas utilizadas mais recentemente, os métodos sem malha vêm ganhando notoriedade, principalmente frente às suas vantagens. Livres da discretização da malha, problemas de superfície livre, mesmo com alta variabilidade, são factíveis. Neste contexto, lança-se mão de um código baseado no modelo SPH (Smoothed Particle Hydrodymanics), desenvolvido no âmbito desta Tese de Doutoramento e validado utilizando casos clássicos da literatura em escoamentos de fluido ideal (ruptura de barragens, geração e quebra de onda e esvaziamento de um reservatório) e real, de reologia newtoniana (Poiseuille com superfície livre, Poiseuille plano, escoamento de Couette e ruptura de barragens). De posse do código numérico, estima-se a altura da onda solitária gerada a partir do impacto de uma massa deslizante em meio líquido. A massa deslizante é representada por duas formas distintas: um bloco indeformável, modelado como um corpo rígido e um fluido ideal. No caso do bloco indeformável, embora o perfil de onda seja bem representado, a altura da ... / Abstract: Landslides that impact into water (such as lakes) can generate waves due to the energy transfer from the solid to the water. These submerged waves, or more specifically solitons, are well known and have been studied for many years specially because of their massive energy and destructive potential. However, analitical approches of this problem are difficult. In another words, the wave's generation phase is complex, primary due to the determination of the free surface (splash) and correlation between the energy of the landslide and the genereted wave. So, numerical methods are an alternative and interesting option. Among the recently used numerical methods, the mesh free has become notorious because of its advantages. Without the mesh restrain, free surface problems are easier to handle. In this context it is proposed a program based on SPH (Smoothed Particle Hydrodymanics) model, developed in this Thesis and tested in different scenarios considering the flow of ideal (dam break, wave generation and wave breaking and reservoir) and newtonian fluids (free surface Poiseuille flow, plane Poiseuille flow, Couette flow and dam break). So, the numerical code is used in order to evaluate the solitary wave height that is generated from the impact of a mass, which represents a landslide in a fluid. The mass is represented by two forms: an undeformable solid block and an ideal fluid. Both forms are tested, and the solitary wave is reproduced, and compared to experiments. Differences are noted among wave heights using a solid block, as reported by the literature. The comparison with the results from the mass represented as an ideal fluid showed a good approach for both the shape and the wave amplitude / Doutor

This thesis concerns the water wave problem corresponding to a piecewise constant vorticity function. There are several results connected to this field. In [1] the authors prove the existence of small-amplitude capillary-gravity water waves in the setting of unidirectional waves, and present an explicit form of the dispersion equation in the case when the vorticity function has two jumps. A two-layer model with constant but different vorticities is studied in [2], while in [3], an analysis of the dispersion equation for a three-layer model is given. In this thesis we first classify all stream solutions to the problem specified above, and then use our classification to prove and analyze solubility of the dispersion equation for a vorticity function with one jump. We do not require streams to be unidirectional (that is, we allow underlying counter-currents and internal stagnation).

This study set out to investigate the shear stress behaviour at the bed under combined wave and current action. The intention of the study was to make experimental measurements to determine how wave and current shear stresses combine, so that theoretical models describing the combined flow condition could be proposed. Two types of experiment were conducted, and theoretical models for the combined flow were assessed. One set of experiments attempted to use a shear plate to make direct measurements of the combined flow shear stress, and of the shear stresses for the component waves and steady currents. This approach failed because the large correction terms introduced by the non-uniform wave pressure field could not be accurately estimated. The second set of experiments used a laser doppler anemometer to make detailed velocity profile measurements over flat sediment beds. The onset of sediment motion was used as a criterion to carefully control the experiments. It is assumed that the threshold of sediment motion represents a specific shear stress intensity at the bed for sediments of narrow size ranges. As the shear stresses can be determined from the velocity fields under waves and currents, their additive nature under combined flow conditions could be investigated. For each sediment size range, it is shown that the same maximum velocity very near the bed can be used to specify the threshold of sediment motion condition for all flow types, be they under waves, currents, or combined waves and currents. It is also shown that the near-bed velocity under a laboratory wave can be predicted accurately from second order wave theory and that the velocity under a current can be predicted from combining Manning's relation with the universal log velocity law. It is further shown that the near-bed velocity under a combined wave and current can be described by the vectorial addition of the maximum component wave velocity and the average component current velocity. The shear stress for the onset of motion is calculated for the steady current using Manning's relation, for the wave by combining the oscillatory shear stress formula with Kamphuis's rough turbulent friction factor relation, and for the combined wave and current by the simple vectorial addition of the component shear stresses, and is shown to be comparable with Shields's threshold criterion for nearly all conditions tested. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science / Vita. / Bibliography: leaves 321-326. / by Teresa Kathleen Chereskin. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1980. / Microfiche copy available in Archives and Science. / Vita. / Includes bibliographical references. / by William Allan Perrie. / Ph.D.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Bibliography: leaves 198-203. / by Dick Kau-Ping Yue. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 91-92. / by François-Marc Turpin. / M.S.

Yes / When ocean waves propagate over porous seabed, they cause variations of the pore pressure within seabed, leading to the possible wave attenuation and soil liquefaction. In order to advance and improve our understanding of the process of wave-induced seabed liquefaction and its impact on wave propagation, systematical experiments are carried out in a wave flume with a soil basin filled with silt. Both the pore pressures and water surface elevations are measured simultaneously, while the seabed liquefaction is videotaped using a high-speed camera. Laboratory measurements show that the pore pressure in surface layer mainly oscillates over time, while the wave period averaged pore pressure has little change. In the deep layer, however, the wave period averaged value of the pore pressure builds up dramatically. The results show that the wave height decreases rapidly along the direction of wave propagation when seabed liquefaction occurs. Such a wave attenuation is greatly enhanced when the liquefaction depth further increases. The experiments also demonstrate that the conditions (wave height and wave period) of incident waves have significant impacts on the wave-induced pore pressures, liquefaction depth and wave attenuation in a silt bed. / National Natural Science Foundation of China (Grant No. 51479053), the 111 Project (Grant No. B12032), the marine renewable energy research project of State Oceanic Administration (GHME2015GC01), the Fundamental Research Funds for the Central University, China (Grant No. 2013B31614), the Colleges and Universities in Jiangsu Province Plans to Graduate Research and Innovation (Grant No. B1504708), and Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University (Grant No: 2016491011).

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