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

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.

A new anisotropic poroelastic damage model is proposed for saturated brittle porous materials. The damage impact on the poroelastic coupling coefficients is investigated. The contribution of pore pressure in damage growth mechanism is identified.

This paper proposes a theoretical framework for the study of contact-wear. Wear phenomena due to contact and relative motion between two solids are characterized by a loss of material. The detached particles as well as damaged contact areas of the solids form an interface with complex mechanical properties. Using an analysis of the dissipation in this interface, an energy release rate and then a wear criterion are defined. This dissipation associated with loss of material will be called wear dissipation. An application to steady-state wear processes is then given.

In the frame of the Restricted Three-Body Problem (plane elliptic case), orbital stability of fictitious planets orbiting one of the two components of a binary star system (known the mass ratio of the two stars and the eccentricity of their orbit) is systematically explored, varying initial coordinates and velocities of the planet. For the first 5 binaries we studied, the main result is that stable planetary orbits exist at large distance from their “sun” ; for 3 of these binaries, some of these stable planetary orbits are nearly circular and, among these latter, several lie inside the habitable zone.

Moreover, extrapolating to exoplanets the known dynamics of the Solar System, we may suspect that a subset of these orbits could be chaotic (and, sometimes, chaos may be bounded). A method to study this possible chaos is to compute Lyapunov Indicators; results of a numerical simulation - over Solar System age - are presented here for a fictitious exoplanet orbiting η CrB A, a planet for which the trajectory reveals bounded chaos caracteristics (during the simulation time span).

We have developed a code based on a mixed Eulerian-Lagrangian approach. The aim of the present paper is to study the influences of interparticle forces in a numerical study of the flow structures of cohesive powders in a dense gas-particle fluidized bed.

Time dependant bottom shear stress under a complex wave given by a JONSWAP spectrum is computed with a turbulent boundary layer numerical model. A parameterized formula enables us to retrieve with a good agreement the time series of the bottom shear stress given by the model from the instantaneous velocity associated to the wave out of the boundary layer, the Nikuradse rugosity and the spectrum peak period.

Knowles and Sternberg gave the definition of the M integral relative to the dilatational symmetry in the elasticity domain. The path domain independence of this integral correspond to some very restricted applications. We propose to enlarge the field of application in defining for every type of transformation a modified path domain independent M integral. The demonstration that this conservation law is associate to the transformation is considered.

The general theory of the diffraction of an electromagnetic plane wave from a bigrating of prolate spheroidal cavities hollowed in a perfectly conducting metallic plate has been carried out and numerical results were recently published.

To valide these numerical results, an experimentation in microwave range with two deep bigratings has been realized. Numerical and experimental results, which concern the efficiency in the (0,0)-order versus the wavelength and for quasi-normal incidence are in a good agreement and allow us to extend the possibilities of our codes.

A geometrical interpretation of intermittency in fully developed turbulence is realized through an hierarchy of fractal structures Ω_p of dimensions Δ_p linked each other by the relations Ω_{p + 1} − Ω_p (i.e. Δ_{p + 1} < Δ_p) and γ = (Δ_{p + 1} − Δ_∞)/(Δ_p − Δ_∞) with γ = ((1 + 3/√8)^1/3 + (1 − 3/√8)^1/3)³ and Δ_∞ = 1 and Δ_∞ = 1. This is obtained by the introduction of an entropy jump, defined at the scale r, ΔS_p(r) = (Δ_{p + 1} − Δ_p) ln (r/r₀) characterizing the order level of each sub-structure Ω_p and verifying a linear relation ΔS_p(r) = γ ΔS_{p − 1}(r).

A criterion is proposed to predict delamination initiation in angle-ply laminates. An analytical model permits to calculate interface stresses between two layers in any laminate. The criterion is based on the maximum value of these stresses and takes into account the scale effects (number of layers). The numerical results are validated by a comparison with experimental data.