Adrien Poupardin

L'etude de la dynamique tourbillonnaire autour des structures immergees dans la mer est entreprise pour comprendre l'impact de ces implantations sur l'environnement. Les tourbillons sont etudies en considerant l'interaction entre une plaque horizontale et une houle monochromatique. Cette houle est generee dans un canal a houle vitre possedant un batteur et une plage d'amortissement. La Velocimetrie par Image de Particule (PIV) et la Stereo-Videographie sont utilisees pour suivre les tourbillons dans leur evolution. La PIV, qui est une technique de visualisation 2D, a permis de montrer que les tourbillons jouent un role essentiel dans la dynamique de l'ecoulement autour de la plaque. En effet, l'ecoulement est tres different de celui predit par les modeles analytiques qui ne prennent pas en compte la dynamique tourbillonnaire. Emis aux bords de plaque, ces tourbillons evoluent par paires et sont advectes dans le sillage de la plaque en amont et en aval. De...

With high anthropogenic pressure and the effects of climate change (e.g., sea level rise) on coastal regions, there is a greater need for accurate and up-to-date information about the topography of these systems. Reliable topography and bathymetry information are fundamental parameters for modelling the morpho-hydrodynamics of coastal areas, for flood forecasting, and for coastal management. Traditional methods such as ground, ship-borne, and airborne surveys suffer from limited spatial coverage and temporal sampling due to logistical constraints and high costs which limit their ability to provide the needed information. The recent advancements of spaceborne remote sensing techniques, along with their ability to acquire data over large spatial areas and to provide high frequency temporal monitoring, has made them very attractive for topography and bathymetry mapping. In this review, we present an overview of the current state of spaceborne-based remote sensing techniques used to est...

The trans-pacific propagation of the 2010 and 2015 Chilean tsunamis have been simulated by resolving both the Saint-Venant and the Boussinesq equations, these latter equations taking into account the frequency dispersion of waves. Numerical results show that the frequency dispersion simulation must be considered to reproduce the wave heights and arrival times recorded by several DART buoys in the Pacific Ocean. Several grid resolutions have been tested using either the Saint-Venant or the Boussinesq model (10', 5' and 2'). Only the Saint-Venant simulation at a 5' resolution and the Boussinesq simulation at a 2' resolution allow to reproduce the amplitudes and arrival times of the first waves. Numerical results indicate that frequency dispersion has a significant impact on the computed waveforms and suggest that the Saint-Venant code generates numerical dispersion similar to the physical frequency dispersion. It has been confirmed by one dimensional sensitivity tests. By comparing both events (2010 and 2015), we show that the frequency dispersion is stronger for the second event and it has been confirmed by the analysis of the Absolute Pressure Gages KSR1 and MRT1 spectrograms at some 17000 km from the source. Indeed, the main wave energy is contained in the first waves for the 2010 events and in the following waves for the 2015 event. Nevertheless, for the 2010 event, we also detect some late arrival waves at the APG KSR1, three hours after the first arrival time, with energy only two times lower than the first wave one.

This paper aims at best describing the submarine landslide which induced partial submersion of the atolls of Mururoa and Fangataufa in 1979. More precisely, waves propagated along the south coast of Mururoa atoll and penetrated into its lagoon some minutes after the landslide triggering (t = 0 s), whereas a train of eight water waves reached the runway located on the north-east coast of Fangataufa (40 km south of Mururoa) between t = 7 min 30 s and t = 20 min. A numerical model based on shallow water equations is used to simulate the landslide as well as the associated tsunami. Saint-Venant equations are used to propagate the tsunami in coastal areas, whereas the offshore propagation is simulated by solving weakly nonlinear Boussinesq equations. Low- and high-resolution nested grids are used to simulate the tsunami propagation in deep sea and in shallow waters, respectively. Several scenarios have been tested to reproduce the observed water and run-up heights in the near and far fields. The best scenarios correspond to a landslide with a volume in the range (75–90 Mm3) (for a basal friction angle of 35°) and with a basal friction angle in the range (30°–40°) (for a volume of 80 Mm3). These results have been completed by a parametric study on the slide parameters.

The interaction of waves and current with submerged structures in coastal zones generates some complex hydrodynamics features which may considerably impact the local environment. The geometrical singularities of the structures produce concentrated vortex filaments which may impact the sea bed and/or the free surface. The objective of the present study is to characterize the vortex dynamics generated by a horizontal plate considered as a vortex generator, in a regular wave field. Vortices are generated at the edges of the plate. They undergo three-dimensional instabilities leading to their destruction. Their dynamics is investigated thanks to laboratory experiments conducted in two different wave flumes to study the impact of the scale on the dynamics. The two-dimensional vortex dynamics is characterized using PIV measurements. Vortex intensity, trajectory and life time are determined. The three-dimensional dynamics is studied thanks to stereo photography. The vortices are visualised...

Within an effort to estimate near-shore bathymetry from satellite scenes, a method based on wave celerity and wavelength estimation is developed. These wave characteristics are extracted from SPOT-5 panchromatic and multispectral scenes. The method allows us to associate the wavelength and the celerity of the same detected wave and to estimate the water depth from the dispersion relation. This technique is tested on Saint Pierre area (La Reunion Island). Results are compared to in-situ measurements and show a reasonable agreement in terms of morphology and a mean absolute bathymetric error inferior to 30 % in intermediate depths (5-30 m range).

The interaction of waves and current with submerged structures in coastal zones generates some complex hydrodynamics features which may considerably impact the local environment. The geometrical singularities of the structures produce concentrated vortex filaments which may impact the sea bed and/or the free surface. The objective of the present study is to characterize the vortex dynamics generated by a horizontal plate considered as a vortex generator, in a regular wave field. Vortices are generated at the edges of the plate. They undergo three-dimensional instabilities leading to their destruction. Their dynamics is investigated thanks to laboratory experiments conducted in two different wave flumes to study the impact of the scale on the dynamics. The two-dimensional vortex dynamics is characterized using PIV measurements. Vortex intensity, trajectory and life time are determined. The three-dimensional dynamics is studied thanks to stereo photography. The vortices are visualised with hydrogen bubbles generated at the edges of the plate by electrolyse. The evolution of the vortices is visualized by two CCD cameras located in different planes. Two most unstable wavelengths are observed which do not seem to depend on the width of the wave flume.