Sourvinou-Inwood Christiane, Hylas, the Nymphs, Dionysos and Others. Myth, Ritual, Ethnicity

Le titre du dernier livre de Chr. Sourvinou-Inwood (C.S.-I.) laisse songeur : on comprend la relation d’Hylas, le premier nommé, avec les Nymphes qui l’ont enlevé, mais que vient faire ici Dionysos qui n’apparaît pas dans sa légende ? Et qui sont ces mystérieux « autres » qui suivent ? Le sous-titre lève un peu le voile en nous indiquant qu’il ne s’agit pas ici de traiter seulement du célèbre mythe (bien connu par l’iconographie, jusqu’au célèbre tableau de Waterhouse daté de 1896 et conservé..

Fluids-membrane interaction with a full Eulerian approach based on the level set method

A fully Eulerian approach to predict fluids-membrane behaviours is presented in this paper. Based on the numerical model proposed by Ii et al. (2012), we present a sharp methodology to account for the jump conditions due to hyperelastic membranes. The membrane is considered infinitely thin and is represented by the level set method. Its deformations are obtained from the transport of the components of the left Cauchy-Green tensor throughout time. Considering the linear or a hyperelastic material law, the surface stress tensor is computed and gives the force exerted by the membrane on the surrounding fluids. The membrane force is taken into account in the Navier-Stokes equations as jump conditions on the pressure and on the velocity derivatives by imposing suitable singular source terms in cells crossed by the interface. To prevent stability issues, an extension algorithm has been developed to remove the normal derivatives of the scalar fields specific to the membrane. In particular, a subcell resolution at the interface of the extrapolated variable is proposed for increasing the accuracy of the extension algorithm. These improvements are validated by comparing our numerical results with benchmarks from the literature. Moreover, a new benchmark is proposed for fluids with both different viscosities and different densities to target applications where a gas and a liquid phase are separated by a membrane

Direct numerical simulation of a bubble motion in a spherical tank under external forces and microgravity conditions

We present, in this paper, numerical simulations of bubble sloshing in a spherical tank, resulting from a tank rotation around a fixed axis in microgravity conditions. This configuration is of great interest in space applications where sloshing can have harmful effects on the stability of satellites. Depending on the dimensionless numbers characterising this phenomenon, our study is focused on the motion and the deformation of a bubble, initially at rest, which is set in motion when the manoeuvre is starting until it reaches a constant rotation speed around the axis. It is shown in this article that, during the first stage of the manoeuvre, the motion of the bubble is essentially driven by the inertial force that depends on the angular acceleration. Next, when the angular velocity is increasing, the centrifugal force being dominant, the trajectory of the bubble is pushed towards the direction between the centre of the tank and the axis of rotation. Finally, when the angular velocity becomes constant, the bubble, reaching a quasi-steady position, is deformed and pressed against the solid boundary of the tank. A quantified description of these phenomena is proposed through a parametric study varying the essential dimensionless numbers, i.e. the Bond number based on the angular velocity, and another Bond number based on the angular acceleration. As the temporal evolution of the forces acting on the satellite wall is of utmost importance for designing satellites and manoeuvres, we also present an analysis characterising the latter. We also detail the first comparisons between the numerical simulations and the Fluidics experiment performed in the International Space Station (ISS) in microgravity conditions. Thanks to these comparisons, we can validate the simulations in configurations of interest

Comparison between the FLUIDICS experiment and direct numerical simulations of fluid sloshing in spherical tanks under microgravity conditions

The fluids behaviour within a spherical tank under microgravity conditions is investigated through a comparison between the original data from the FLUIDICS experiment carried out in the ISS and Direct Numerical Simulations for two-phase flows. The study case consists in the rotation of a spherical tank around a fixed axis. The tank is filled with a liquid with physical properties similar to those of liquid propellants and gases used in the space industry. Two tanks with different filling ratios have been tested in space. Cameras and sensors allow extracting the fluids dynamics and the temporal evolution of the force and torque exerted by the fluids on the tank wall. Several manoeuvres corresponding to different angular velocities and angular accelerations are submitted on both tanks. The velocity profile is divided into four phases: from zero, the angular velocity around the vertical axis increases linearly until it reaches the required constant value for which the fluids stabilise in the second phase, then the angular velocity decreases until it recovers zero. Numerical simulations are computed with the home-made code DIVA which is based on the Level Set method coupled with the Ghost Fluid Method. The force in the radial direction gives the value of the centrifugal force during the constant angular velocity phase. The average centrifugal force is well predicted by the simulations, the comparison with the experimental data exhibits errors lower than 3% for the half-filled tank. Considering the vertical torque, the effect of the Euler acceleration is clearly visible through the important peaks of opposite sign observed during the acceleration and the deceleration phases. Moreover, the oscillations of the gas bubble during the second phase can be observed from the torque evolution. Their magnitude decreases throughout time until the steady state is reached. The measured and predicted temporal evolutions match together until the magnitude of the oscillations reaches the noise level of the data. The bubble oscillations are much more damped for the tank containing a larger amount of liquid (75%). The frequency of these oscillations are investigated applying the Fourier transform of the torque signals and by looking at the videos taken during the experiment. Similar oscillation frequencies are observed with the experimental setup and the numerical simulations, even for the manoeuvre with the lower Bond numbers. We verify that the oscillation frequency increases with the angular velocity. Finally, the comparison exhibits that the numerical simulations provide an accurate prediction of the fluids behaviours in microgravity conditions for this range of Bond numbers

Développer la médiation documentaire numérique

Depuis quelques années, les bibliothèques investissent fortement l'Internet : catalogues en ligne, sites Web devenant peu à peu des portails de services, blogs et réseaux sociaux. Si l'objectif est bien d'être présent dans l'univers numérique des usagers existants ou potentiels, les bibliothèques, aussi bien universitaires que de lecture publique, doivent garder leur spécificité sous peine d'être noyées dans le flot général. L'un des axes de travail pour ce faire est de transposer en ligne la médiation documentaire, c'est-à-dire repenser pour l'Internet tous les moyens à mettre en œuvre pour favoriser la rencontre d'un lecteur avec les documents susceptibles de l'intéresser ou de lui ouvrir de nouveaux horizons. L'ouvrage traite de ce nouvel enjeu en proposant d'une part, un cadre général sur la médiation documentaire numérique (quelle politique documentaire favoriser ? Comment scénariser son catalogue, médiatiser un fonds patrimonial ou de jeux vidéo ? Comment définir son projet et accompagner les équipes ?) et d'autre part, des exemples concrets destinés à servir d'inspiration pour améliorer ou se lancer dans ce continent en pleine construction (quels contenus produire ? Quels outils utiliser ? Comment rédiger un billet de blog, un article de magazine en ligne, des coups de cœurs 2.0 ?). Coordonné par Xavier Galaup, directeur-adjoint de la médiathèque départementale du Haut-Rhin, ce volume collectif, qui réunit des auteurs d'horizons divers (universitaire, bibliothécaire et libraire), s'adresse à tous les acteurs des domaines de la culture et de l'éducation

Les Nymphes entre maternité et courotrophie dans les Hymnes homériques

The study of four Homeric hymns reveals some versatility of Nymphs with regard to their maternal and courotrophic functions. In the Homeric Hymn to Hermes, Maia is both a mother and a nurse, combining biological and social motherhood. The Homeric Hymn to Aphrodite offers the first occurrence of nursing Nymphs, but one of the Idaean Nymphs is supposed to be Aeneas’ mother, as the role of Aphrodite remains concealed. The courotrophic function is also attested in the Homeric Hymn to Dionysus, but Nymphs continue to follow the god after raising him, taking part in his thiasos. Finally, the Homeric Hymn to Pan shows an example of biological motherhood without social motherhood, the young mother rejecting her child. Despite the variety of these different roles of mother and nurse, there is some constancy in the mode of action of the Nymphs, which seems to be characterized by a form of care in hiding, making these deities mediating entities protecting the transition between two statuses, from childhood to adulthood

Les Nymphes dans les rites du mariage

Marriage, where the Nymphs appear both as supernatural powers and as human numphai, is a rich intersection of literary, archaeological and epigraphic data concerning the cult of the Nymphs. Preliminary rites for the Nymphs might consist in proteleia sacrifices, loutrophoria and premarital baths. Nymphs are not usually present during the wedding day, except in those literary texts which cannot be considered as evidence of actual cult practice. Postnuptial offerings might also be made to these deities, as in the sanctuary of the Nymph in Athens, where several loutrophoroi were discovered, or in some Attic caves. Nymphs act primarily through the life-giving and nurturing qualities of fresh water, enhancing the beauty of the numphe, facilitating the transition between the two states, and increasing the fertility of the bride