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

A recently established variational procedure is used to compute self-consistent estimates for viscoplastic polycrystals with highly anisotropic ionic and HCP grains. For large values of the grain anisotropy M, the predictions for the macroscopic flow stress are found to scale as M^γ, where γ depends on the number (less than 5) of independent slip systems that are available for plastic flow, but not on the strain-rate sensitivity. The predictions of other nonlinear extensions of the self-consistent scheme are inconsistent with this scaling law, suggesting that they may be less accurate than the variational estimates proposed here.

Turbulent two-dimensional incompressible flows are studied by means of a mixed Euler-Lagrange method. Transported properties are the vorticity ζ the turbulent kinetic energy k, and a turbulent characteristic frequency ω. This approach avoids the use of a permanent grid and the discretization of the convective terms. It is suitable for multibody configurations, particularly when wake/body interaction occurs.

The finite element solution of Helmholtz equation is dispersive and the existent a posteriori error estimators underestimate the pollution error implied by this phenomenon. In this paper, a new type of residual estimator for the Helmholtz operator is proposed and tested on a one-dimensional model problem. The numerical results show that the error is correctly estimated but new difficulties appear in the exact evaluation of problem dependent constants.

A measurement technique of heated droplets temperature, based on two tracers laserinduced fluorescence is presented. This method appears particularly interesting in the field of experimental studies carried out in spray combustion, where fuel is injected in the combustion chamber on a droplet form.

We present the two-dimensional solutions of the radiative transfer equation for any inhomogeneous rotationally symmetrical and isotropic semitransparent medium. The medium is considered non-scattering and limited by a purely specular boundary.

Numerical simulation of complex flows involving unsteady structures, boundary layers or free surfaces on a unique grid is very greedy in time and CPU because a great number of calculation point is needed to ensure a satisfactory description of the different scales of the problem. An original local multigrid method, able to refine the grid at the cell scale, is proposed to solve the Navier-Stokes and energy equations. The results obtained for the natural convection in a square cavity are compared to the one of the literature for Rayleigh numbers in the range 10⁵–10⁸.

We consider a slender particle of straight centre-line (the line to which it collapses as its slenderness ratio ɛ vanishes) and of possibly non-uniform zeta potential. The body, not necessarily of circular cross-section, is embedded in a given electric field of revolution about the centre-line. Under those assumptions, this work asymptotically approximates, with respect to ɛ, the electrophoretic motion of the particle.

A multidomain/multiresolution technique is developed, with application to large-eddy simulation. A general framework for the definition of the exchange of information at the interface is proposed. It relies on the definition of some interface variables, which enables the construction of the transfer operator at the interface. The method is successfully assessed on a subsonic plane channel flow.

In the study of the cutting, we develop a model for the contact between ship and tool based on the notion of stress couple. We present the main hypotheses for the associated 3D analytic model and the results arising premil.