PhD defense - Nicolas DESMARS - LHEEA/ED SPI

Committee

• Vincent Rey (Mediterranean Institute of Oceanography) - Reviewer
• Karsten Trulsen (University of Oslo) - Reviewer
• Stéphan Grilli (University of Rhode Island) - Examiner
• Olivier Kimmoun (Centrale Marseille) - Examiner
• Agnès Maurel (CNRS) - Examiner
• Pierre Ferrant (Centrale Nantes) - Thesis director
• Guillaume Ducrozet (Centrale Nantes) - Co-advisor
• Yves Perignon (CNRS) - Co-advisor

Due to the current health situation, only a remote Zoom access will be available to the public:

https://ec-nantes.zoom.us/j/94224493348
ID de réunion : 942 2449 3348  
 

Abstract

Researches conducted in this thesis address the problem of deterministic prediction of ocean wave fields around a marine structure, a key parameter for the analysis and control of a vast range of offshore operations, on the basis of datasets acquired remotely by an optical sensor. Efforts focus on the inclusion, at low computational cost, of the modeling of nonlinear hydrodynamic phenomena, preserving the reliability the surface representation in case of severe sea state.
A weakly nonlinear Lagrangian approach (ICWM), whose hydrodynamic properties are evaluated by intercomparison with reference wave models, is selected for the description of the free surface. The prediction problem is then formulated as an inverse problem that aims at fitting the solution described by the wave model to observations, here composed of free surface elevation datasets generated by a synthetic, yet realistic, lidar sensor
scanning the ocean surface at grazing angle. Predictions are then issued through the propagation in time and space of the parameterized wave model.
The applicability of the methodology is validated using observations of both unidirectional and directional wave fields, obtained at different instants to compensate for their strong spatial non-uniformity. The relative performance comparison between ICWM and lower-order wave models highlights the improvements due to the modeling of wave nonlinearities, especially those pertaining to the correction of the dispersion relation. A
demonstration of the usefulness of ICWM is then provided by means of a procedure that is fully validated experimentally in a wave tank.

Keywords: Ocean waves, Gravity waves, Deterministic prediction, Nonlinear waves, Hydrodynamics, Inverse problem