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Theses

Modélisation de la propagation de la houle en présence de courants cisaillés et par bathymétrie variable

Abstract : This PhD thesis focuses on a specific part of the interactions between waves, current and bathymetry: the influence of the vorticity on the Bragg resonance phenomenon. Two numerical models, based on hyperbolic equations, are compared: the Mild Slope equation and the Modified Mild Slope equation, both extended to consider vorticity. To establish some trends about the wave behaviour in such configuration, the influence of the vorticity has been compared to the influence of the surface current velocity, in a parametric study. To go further, an experimental campaign has been settled in a wave flume, and the reflexion of regular waves propagating above sinusoïdal bathymetry and horizontally varying sheared currend has been registered for a large range ofwaves frequencies. Sorne strong conclusions asserted themselves: under the influence of a varying sheared current, the maximum of reflexion is reduced, both in amplitude and frequency, but another local maximum appears in higher waves frequencies (between 1.25 and l .45Hz). Moreover, our modelling achieved to represent the amplitude of the Bragg Peak quite well, but always overestimated the associated frequency. Thanks to a strong questioning of the theory and a collaboration between several researchers, a new modelling arised, with an original decomposition of the velocity potential taking into account the asymmetry between the incident and reflected wavenumbers. The first results are very optimistic: find the Bragg Peak frequency is not a problem anymore, and the study on the vorticity influence can continue. This new approach in coastal engineering will generate as many questions as opportunities.
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Elodie Laffitte. Modélisation de la propagation de la houle en présence de courants cisaillés et par bathymétrie variable. Autre [q-bio.OT]. Université de Toulon, 2018. Français. ⟨NNT : 2018TOUL0017⟩. ⟨tel-02484402⟩

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