Comptes Rendus de l'Académie des Sciences - Series IIB - Mechanics-Physics-Astronomy最新文献

Interaction experiments between an internal solitary wave and a monochromatic surface wave have been carried out in a salted stratified medium. Strong (resp. weak) interactions showed that surface wave amplitude decreases (resp. increases) were much larger than predicted by wave action conservation applied to the refraction on slowly varying currents.

We show that when (ΩR/c₀) ≪ 1, and (a/R) ≪ 1, the air motion in a torus is governed by the problem of inertial oscillations in this torus excited by a perturbation on its surface, which moves with constant angular velocity Ω and gets recurrently at the same place with period 2π/Ω. This excitation makes one of the inertial oscillation modes enter in resonance, the geostrophic mode, which increases proportionally to time when t → ∞.

This Note is concerned with the development of variational estimates for the effective stored-energy function of hyperelastic composites undergoing finite deformations. It makes use of a suitable generalization of the “second-order procedure” of Ponte Castañeda, the key idea being the introduction of an optimally chosen “linear thermoelastic comparison composite”, which can then be used to convert available homogenization estimates for linear systems directly into new estimates for hyperelastic composites. The resulting estimates are known to be exact to second order in the contrast. An application is given for particle-reinforced rubbers.

The settling velocity of isolated spherical particles, in grid generated turbulence, points out the role of the vortex structures in sediment process. The analysis of mean and turbulent velocities fields shows that the ratios between turbulence scales and characteristics of the particles are of great importance on the settling velocity evolution.

One studies crack kinking from an interface crack when this crack is closed prior to kinking but open after it. Contact is assumed to occur without friction. This problem was considered very recently by the authors in the special case of some homogeneous material (ordinary crack). One establishes the relation between the stress intensity factors just before and just after the kink. From there, and using Goldstein and Salganik's famous principle of local symmetry, one derives the value of the kink angle. This value is somewhat surprisingly found to depend only very weakly on the mismatch of elastic properties between the materials.

The fatigue growth path of an arbitrary plane crack, loaded by some remote tensile uniform stress, is computed using a perturbation method derived from the three-dimensional weight-function theory of Rice (1985, 1989). First, the stress intensity factor and the weight function of the initial front are calculated. Then, the crack advance is determined by applying Paris' law. One advantage of the method is that only the meshing of the initial front is needed, allowing for the study of propagation on a large scale.

A very thin superfluid film on a weakly attractive surface (such as rubidium metal) should display an unusual vortex structure, with a dry core larger than the standard core radius λ. In this structure, the capillary energies are slightly increased, but the vortex kinetic energy is reduced.

The overall representation of the four elliptical hodographs corresponding to Miller's observations reveals remarkable regularities. The centres of the hodographs are located on a circle and for each sidereal time the points corresponding to Miller's four dates are themselves located on a circle. The gaps in relation to these circles are very slight in relative terms. These regularities confirm the existence of a very coherent structure subjacent to Miller's observations.