Speaker : Laurent Chemin (Universidad Andres Bello, Instituto de Astrofisica)
Title: Dynamics of the Milky Way and LMC as seen by Gaia
Abstract:
Speaker : Philippe Bonneton (EPOC, CNRS/U. Bordeaux)
Title: Tidal bore dynamics in estuaries
Abstract: A tidal bore is a sudden elevation of the water surface that travels upstream an estuary with the incoming flood tide. The formation and dynamics of this spectacular and fascinating phenomenon bring into play nonlinear wave interactions over a large range of spatiotemporal scales. A tidal bore is a small-scale estuarine process with scales of variation of order few seconds in time and dozen meters in space. This small-scale process, which generally occurs in the upper estuary, results from the nonlinear transformation of the tidal wave over long distance (several dozen of kilometers) and long period of time (several hours). The general bore phenomenon has been extensively studied in fluid mechanics and mathematics. On the other hand, the large-scale mechanisms which control tidal bore formation has so far received little attention. In this presentation we will analyze tidal bore formation from a unique long term database acquired during 4 campaigns in the two main French tidal-bore estuaries: the Seine and Gironde/Garonne estuaries. We will show that the tidal bore intensity is mainly governed by the dimensionless tidal range, which characterizes the local tidal wave nonlinearity. We will also show that the undular bore structure can be explained by two different wave processes depending on the bore intensity.
Speaker : Camille Bergez-Casalou (LESIA)
Title: Simultaneous accretion of giant planets or how giant planets fight for food
Abstract: Among the thousands of exoplanetary systems observed nowadays, some of them host multiple giant planets, like in our Solar System. These giants are probably formed from the same protoplanetary disc. I’m going to present our recent paper where we investigated, with the help of 2D hydrodynamical simulations, how the gas present in the protoplanetary disc is distributed and accreted by two planetary cores. We start with 20 Me cores undergoing runaway gas accretion and follow the evolution of the planets mass ratio. We find that when the planets accrete from the same disc, they end up with very similar masses, independently on the disc viscosity or the delay in accretion between the planets. We finish by suggesting different formation scenarios in order to explain the observed exoplanets distribution.