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

The rotating flow inside an enclosed cylindrical rotor–stator cavity is studied. Within a certain range of governing parameters, vortex breakdown phenomenon can arise along the axis. Very recent papers exhibiting some particular three-dimensional effects, have concentrated new interest on this topic. The study is carried out by a numerical resolution of the 3D Navier–Stokes equations, based on spectral approximations. Three-dimensional behaviours of the flow and in the structure of the associated vortex breakdown are numerically exhibited for the first time in a cavity of large axial aspect ratio.

The theoretical development of a combined method of moiré interferometry, Twyman–Green interferometry and incremental hole-drilling method is presented. The relationship between the three-dimensional surface displacements produced by introducing a blind hole and the corresponding residual stress is established by employing the existing theoretical solution containing a set of undetermined coefficients. The in-plane surface displacements $\text{U}{}_{\mathrm{x}}$ and $\text{U}{}_{\mathrm{y}}$ and out of plane surface displacement $\text{U}{}_{\mathrm{z}}$ produced by the relaxation of residual stresses are obtained from moiré interferometry and Twyman–Green interferometry respectively. The accuracy of the method and the experimental procedure to determine the signs of residual stresses are described. A typical examp1e is presented.

Two color laser-induced fluorescence technique is able to measure mean temperature of flying droplets, in the evaporation regime without combustion. This paper presents preliminary results about the use of this technique in reactive media.

An original reformulation of the viscous stress tensor is proposed for the motion equations dedicated to an incompressible fluid. Four different tensors appear in this decomposition, associated with viscosities of compression, elongation, shearing and rotation. This new model allows us to build a numerical solver of the Navier–Stokes equations based on a technique of tensorial penalization which is generalized with all the stresses acting on a flow. The processing of incompressibility and the rotation of a rigid body in a flow are described thanks to the model. Several numerical applications are proposed to illustrate the abilities of the new penalization method.

Wall effects on electrophoretic motion of a non-conducting particle are investigated by resorting to a boundary integral approach. Contrary to available works in the field, our method applies to a particle of arbitrary shape and zeta potential. Morevover, it circumvents calculating the perturbation potential and the fluid flow. Enclosed numerical results emphasize that, near the plane boundary, wall–particle interactions may strongly modify the electrophoretic motion taking place for a single sphere.

It is shown in this note that the recently proposed ‘second-order’ homogenization method can violate a rigorous bound, when used together with the self-consistent approximation for the relevant ‘linear comparison composite.’ Although the second-order method is known to yield quite accurate results for small to moderate volume fractions of the phases, even for high nonlinearity and high contrast situations, it is shown here to fail near the percolation limit, where it can violate the bound for any level of nonlinearity. This suggests that the second-order method should be amenable to improvement to account for the effect of strong field fluctuations near the percolation threshold.

Calorimetric effects related to the propagation of a phase change front in a monocrystalline shape memory alloy CuZnAl were derived from thermographic data analysis. At constant load, the displacement of the front induces a creep of the sample strongly depending on thermal exchanges with the surroundings. The main role played by the thermomechanical couplings can be pointed out by reversing the heat flux at the boundary of the sample: this leads to an inversion of the front propagation way associated with a recovery of the creep strain.

We propose a new model for laminated plates which can handle high transverse shear effects. The assumptions of the model are stated on the 3D strains. The stress field is in exact equilibrium with prescribed forces except near free boundaries. The stress-strain law is fulfilled. An iterative scheme is used to solve the problem. A comparison with finite elements computations is performed.

This paper presents the equations of motion of an air saturated rectangular porous plate. The model is based on a mixed displacement–pressure formulation of the Biot–Allard theory [1]. We obtain a system of equations which describe the coupling beetween the solid and fluid phases of the plate. This system is solved by applying the Galerkin method.

An air flow crossing two baffles in tandem inside a duct, generates strong self-sustained tones. Four radial slots created on the upstream baffle, leads to a large hysteresis loop of the sound pressure level when velocity varies, the second branch of which corresponds with a reduction of the self-sustained tones. Measurements of velocity show that a Coanda effect happens on the jets issued from the slots, which induces this flow behaviour.