Apport des analyses rheologiques dans l'étude d'émulsions multiples H/L/H

Resume L'objectif de ce travail a consisté principalement à démontrer l'intérêt et le caractère polyvalent des analyses rhéologiques dans l'étude des émulsions multiples H/L/H. En utilisant la grande diversité des tests rhéologiques, il a été possible de charactériser la structure de l'émulsion multiple, d'étudier sa stabilité dans le temps et sous l'effet d'un cisaillement, et encore de charactériser une cinétique de liberation par gonflement puis rupture des globules.

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The main goal of this paper consisted in demonstrating the interest and the versatile nature of the rheological analysis for studying W/O/W multiple émulsions. Using a significant variety of rheological tests, it was possible to characterize the multiple Emulsion structure, to follow its evolution produced by aging or by shear, and to characterize swelling-rupture release kinetics.

     

Numerical calculation of wall effect and ‘backflow’ on the Stokes force

We give numerical results on the modification of the drag force F_x exerted on a sphere positioned eccentrically and moving at very low Reynolds number, at constant velocity within and along a cylindrical tube. The numerical results computed by Lattice-Boltzmann method or by finite volume formulation are in good agreement with the experimental results obtained by Ambari et al. (J. Fluid Mech. 149 (1984) 235–253). In particular, they confirm the existence of a minimum of the force F_x away from the axis of the cylinder and a sharp increase when the sphere approaches the sidewall. To cite this article: T. Godin et al., C. R. Mecanique 330 (2002) 837–842.     

Experimental study of a hypersonic shock layer stability on a circular surface of compressionL'étude expérimentale de la stabilité d'une couche de choc hypersonique sur une surface circulaire de compression

The method of electron-beam fluorescence is applied to study the evolution of natural and artificial periodic disturbances on a developed streaky structure in the shock layer on a circular compression surface model. The model is exposed to a hypersonic nitrogen flow with a Mach number M_∞=21 and unit Reynolds number Re_1∞=6×10⁵ m^?1. Data on the effect of surface curvature and temperature on disturbance characteristics are obtained. To cite this article: S.G. Mironov, V.M. Aniskin, C. R. Mecanique 332 (2004).     

Simulation du front d'écoulement dans les procédés de moulage des composites liquides

This work proposes a procedure of finite difference discretized in a system of curvilinear coordinates adapted to the shape of the saturated zone, to simulate a flow in the LCM (Liquid Composites Molding) process. Formulation and the numerical application of the procedure are described. We describe two configurations of injections. A good agreement is found between numerical, analytical and literature experimental results. To cite this article: M. Hattabi et al., C. R. Mecanique 333 (2005).     

Étude tridimensionnelle des contraintes de cisaillement à la paroi dans un tube de section droite non circulaireThree-dimensional study of wall shear stresses in a tube of noncircular cross-section

This paper describes numerical solutions of the Navier–Stokes equations for incompressible steady flow through a rigid smooth straight tube with an axially uniform non-circular cross section which mimics collapsed veins at peculiar values of the transmural pressure. One of the peculiar values of the transmural pressure produces a contact of the opposite walls along a straight segment. This article deals with the space variations of the wall shear stress induced along the wetted perimeter of the cross section as well as in the streamwise direction especially in the entry length. The motivation of this study is to provide the data for experimental works on flow-subjected endothelial cell culture when the space variations of the wall shear stress are non-uniform. To cite this article: S. Naili et al., C. R. Mecanique 330 (2002) 483–490.     

Numerical simulation of polyhedral crystal growth based on a mathematical model arising from non–local thermomechanics

In this work we present some results of the numerical simulation of the growth of a crystal from its melt, taking into account faceting. The simulation is based on a numerical solution of a three–dimensional generalized Stefan problem. That problem arises from a non–local thermomechanical theory applied to a continuous system with an interface and embodies ideas from the dislocation theory of crystal growth. In the model, the crystal surface is an isotherm and the growth velocity of a crystal face depends on the velocities of the other faces and on the whole crystal configuration as well as on the temperature gradient. A front fixing formulation of the model is considered. This is a conservative form of the Isotherm Migration Method [6, 7, 8, 9, 10, 11] in spherical coordinates. The numerical solution is based on an explicit finite difference discretization of the resulting non–linear equations. We develop a theoretical analysis of the interface equations that drive the crystal face motion. Numerical results, showing evolution of complex crystals with configuration changing during the growth, are in accord with experimental results. Furthermore, numerical experiments offer useful information on the influence of certain parameters in the model on the growth process. Received: March 21, 1996     

Flow stability analysis and excitation using pulsating jets

Classical flow stability applied to transition from laminar to turbulent flow may also describe the behavior of vorticity fluctuations created by a pulsating jet placed along a solid boundary. A numerical laminar flow experiment involving a pulsating jet placed along the surface of a duct with flow separation downstream, resulted in eliminating most part of the separated flow region. Applying the same approach to a turbulent flow, it was possible to develop a turbulent stability flow formulation and apply successfully turbulent pulsating jet flow separation control. To cite this article: D. Skamnakis, K. Papailiou, C. R. Mecanique 333 (2005).     

Visualisation de l'écoulement de Taylor–Dean ouvert

Results of flow visualisation in a Taylor–Dean open device are given. Observations made at the inlet, the core and the outlet of the flow show that different flow patterns can develop simultaneously. The formation and the growth of the structures observed versus control parameters are described. To cite this article: A. Ait Aider et al., C. R. Mecanique 333 (2005).     

一类广义Ball曲线的改进

Said将Ball基由三阶延伸到奇数阶。本文在任意阶上讨论广义Ball曲线性质及其求值的新一种递归算法。     

带税率的Cramér-Lundberg风险模型的总征税次数的分布函数(英文)

本文研究了带税率的Cramér-Lundberg风险模型.利用迭代算法及该过程具有的的强马氏性,得出了保险公司从开始营运到破产期间总赋税次数的概率函数.作为例子,本文给出了指数分布索赔假定下该概率函数的具体表达式.