The effect of wind on modulational instability of gravity waves is presented. A forced nonlinear Schödinger equation that governs the evolution in deep water of weakly nonlinear packets of surface gravity waves under wind forcing is derived. Stokes waves are shown to grow exponentially following Miles' linear mechanism, while modulational instability becomes explosive.
When a rigid cone is slowly pushed through a thin elastic sheet, the material breaks, exhibiting a network of cracks expanding in the radial direction. Experiments conducted with aluminum sheets show that the number of cracks is selected at the beginning of the perforation process and then remains stable. A simple model predicts the number of cracks as the result of a competition between the elastic energy stored in the sheet, and the energy dissipated during crack extension.
Within the framework of nuclear accident scenarios, the initial contamination of continental hydrosystems is essentially from surface deposition of atmospheric aerosols. Whereas the deposition velocities were recently widely studied for meadows, forest and urban forest canopies, the aerosol deposits on hydrosystems need more specific investigations.
Experiment were conducted in the ESIM wave tank in Marseilles in order to study the space/time evolution of the flow field under waves breaking on an 1/15 beach slope. Fluid particles velocities were measured at different depths, before, during and after the breaking event using the Particle Imaging Velocimetry (PIV) technique. The mean and fluctuant components of the flow were calculated.
This research deals with the validation of fluid dynamic models,used for simulating shoaling and breaking solitary waves on slopes,based on experiments performed at the Ecole Sup'erieure d'Ing'enieurs deMarseille's (ESIM) laboratory. A separate paper, also presented at thisconference, reports on experiments.
Des mesures de champs de vitesses utilisant la technique de vélocimétrie par image de particules ont été réalisées pour des vagues déferlantes sur une plage inclinée. Le problème dans ce type d'écoulement est que pour obtenir une définition suffisante en vitesse, la taille des images de mesure doit rester petite, alors que le phénomène observé prend place sur plusieurs longueurs d'onde.
In the case of an accidental or chronic atmospheric pollution by a nuclear plant, aerosols' deposition transfer coefficients must be known. A major issue is to determine the impact of aerosols contained in the radioactive plume on urban areas with the smallest uncertainties.
The formation of aneurysm of abdominal aorta (AAA) is a multifactorial and predominantly degenerative process that results from a complex interplay between biological processes in the arterial wall and the haemodynamic stimuli on the wall, i.e. wall shear stresses (WSSs) and elongations of the wall directly applied on vascular endothelial cells (ECs) partly regulate the arterial wall remodelling (Golledge et al. 2006; Humphrey and Holzapfel 2012).
We prove that the weak Riemannian metric induced by the fractional Sobolev norm $H^s$ on the diffeomorphisms group of the circle is geodesically complete, provided $s>3/2$.
The input of energy by wind to water waves is compared with the observed growth of the waves using a suite of microphysical measurement techniques in the laboratory. These include measured tangential stresses in the water and air immediately adjacent to the interface with corresponding form drag measurements above wind-forced freely-propagating waves.