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Modélisation déterministe des états de mer - Application à la rétrodiffusion d'ondes radar

Abstract : Researches conducted in this thesis deal with the realistic evolution of wave fields in oceanic conditions. The interest is more particularly focused on various aspects including specificities of a deterministic fully non-linear approach, the wind wave coupling and energy dissipation through white capping, and non-linear simplified modeling for operational use. This work aims to provide efficient and realistic modeling of wave fields so as to enable a better understanding of radar backscattering over oceanic surfaces. Direct applications include short-term forecasts of sea states, or detection of marine targets thanks to remote sensing. A numerical tridimensional model based on a High Order Spectral (HOS) method enables to fully account for non-linear processes in sea states. Some specificities are enlighten and provide a better framework for the efficient use of the method. Among them, the need for reference conditions at early stages of a modeled sea state is underlined. A non-linear method is proposed and its performances evaluated. Momentum transfers associated with wind forcing and dissipation through whitecapping are then proposed for the HOS deterministic approach. Two way coupling between atmospheric and oceanic layers, and dissipation of energy due to wave breaking are achieved thanks to a formulation at use in common stochastic wave models. Forcing and dissipation intervene in the HOS formulation by the mean of pressure fields related to the sea state. The recent set of parametered proposed bay Bidot et al.(2005) is tested and comparatively validated with the WaveWatch3 stochastic wave model. The HOS deterministic approach is finally able to properly take into account the evolution of oceanic wave field under wind forcing and dissipation. The problem of simplified modeling of sea state for the specific purpose of operational use in remote sensing applications is finally studied. A numeric method able to take into account non-linear specificities of the wave field up to a second order in wave elevation and third order in term of phase velocity is proposed and implemented. Its performances are comparatively evaluated with fully non-linear evolutions as references.
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Submitted on : Tuesday, December 13, 2011 - 1:11:11 PM
Last modification on : Wednesday, April 27, 2022 - 5:05:00 AM
Long-term archiving on: : Thursday, March 30, 2017 - 8:28:17 PM

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  • HAL Id : tel-00624645, version 2

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Yves Perignon. Modélisation déterministe des états de mer - Application à la rétrodiffusion d'ondes radar. Dynamique des Fluides [physics.flu-dyn]. Ecole Centrale de Nantes (ECN), 2011. Français. ⟨tel-00624645v2⟩

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