A Positive and Entropy-Satisfying Finite Volume Scheme for the Baer-Nunziato Model

We present a relaxation scheme for approximating the entropy dissipating weak solutions of the Baer-Nunziato two-phase flow model. This relaxation scheme is straightforwardly obtained as an extension of the relaxation scheme designed in [16] for the isentropic Baer-Nunziato model and consequently inherits its main properties. To our knowledge, this is the only existing scheme for which the approximated phase fractions, phase densities and phase internal energies are proven to remain positive without any restrictive condition other than a classical fully computable CFL condition. For ideal gas and stiffened gas equations of state, real values of the phasic speeds of sound are also proven to be maintained by the numerical scheme. It is also the only scheme for which a discrete entropy inequality is proven, under a CFL condition derived from the natural sub-characteristic condition associated with the relaxation approximation. This last property, which ensures the non-linear stability of the numerical method, is satisfied for any admissible equation of state. We provide a numerical study for the convergence of the approximate solutions towards some exact Riemann solutions. The numerical simulations show that the relaxation scheme compares well with two of the most popular existing schemes available for the Baer-Nunziato model, namely Schwendeman-Wahle-Kapila's Godunov-type scheme [39] and Toro-Tokareva's HLLC scheme [42]. The relaxation scheme also shows a higher precision and a lower computational cost (for comparable accuracy) than a standard numerical scheme used in the nuclear industry, namely Rusanov's scheme. Finally, we assess the good behavior of the scheme when approximating vanishing phase solutions

Un modèle hyperbolique diphasique bi-fluide en milieu poreux

International audienceAn hyperbolic two-fluid model in porous medium We introduce an hyperbolic two-fluid two-pressure model to compute unsteady two-phase flows in porous media. The closure laws comply with the entropy inequality, and a unique set of jump conditions holds within each field.On introduit dans cette note un modèle d'écoulement bifluide hyperbolique pour simuler les écoulements diphasiques en milieu poreux, en configuration instationnaire. Les lois de fermeture proposées sont consistantes avec l'inégalité d'entropie, et les relations de saut sont uniques champ par champ

A rough scheme to couple free and porous media

International audienceThis paper is devoted to the computation of flows between free and porous media separated by a thin interface . The basic strategy relies on some ideas developed earlier by J.M. Greenberg and A.Y. Leroux on their work on well balanced schemes. This approach requires introducing a set of partial differential equations at the interface, in order to account for the sudden change of medium. The main features of the interface PDE are investigated. We afterwards propose to compute approximations of solutions with help of an approximate Godunov scheme. A linear interface Riemann solver is introduced, which aims at enforcing the continuity of the two (steady wave-) Riemann invariants. Numerical computations involving shock waves or rarefaction waves are examined and the agreement with the entropy inequality is tracked. Effects of the mesh refinement and the impact of the smoothing of the thin interface are also adressed in the paper

A new approach for three-phase flows

International audienceWe present here a new model to describe three-field patterns or three-phase flows. The basic ideas rely on the counterpart of the two-fluid two-pressure model which has been introduced in the DDT framework, and more recently extended to water-vapour simulations. We show the system is hyperbolic without any constraining condition on the flow patterns. A detailed investigation of the structure of the Riemann problem is achieved. Regular solutions of the whole are in agreement with physical requirements on void fractions, densities and internal energies for a rather wide class of equations of state. Even more, this approach enables to perform computations of standard single pressure three-phase flow models, using relaxation techniques and coarse meshes. A few computational results confirm the stability of the whole approach

An hyperbolic three-phase flow model

International audienceWe introduce an hyperbolic entropy-consistant model to describe three-phase flows, which ensures that void fractions, mass fractions and pressures remain positive through single waves occuring in the one dimensional solution of the Riemann problem

A class of compressible multiphase flow models

International audienceWe propose in this note a class of entropy-consistent hyperbolic models for multi-phase barotropic flows. Relevant closure laws are derived and discussed

Mouen – Rue Pierre-Castel

L’opération de diagnostic prescrite sur la seconde phase d’aménagement du lotissement du Lieu Castel à Mouen concernait une surface d’environ 2 ha située immédiatement à l’est des terrains actuellement en cours d’aménagement et étudiés en 2012. Les sondages de 2013 ont permis de repérer plusieurs trames de fossés, sans doute parcellaires, attribuables pour l’une à la Protohistoire et plus vraisemblablement à l’âge du Fer, et pour les deux autres, à la période gallo-romaine. Les fossés protohi..

Cagny – Extension Décathlon

Date de l'opération : 2007 (EX) Inventeur(s) : Hérard Agnès (INRAP) La société Décathlon ayant reçu l’autorisation de construire un entrepôt logistique sur les parcelles n° 62 et 142 de la section cadastrale D de la commune de Cagny, une opération de diagnostic archéologique a été confiée à l’INRAP en préalable à la réalisation de ce projet. Ce dernier concerne une surface de 170 193 m2 située à l’ouest de la commune, à l’angle de la route départementale 230 allant à Giberville et de la route..

Bernières-sur-Mer – Le Clos du Pavillon et Le Camp de Pie

Date de l'opération : 2007 (EX) Inventeur(s) : Hérard Agnès (INRAP) La société Investir Immobilier ayant reçu l’autorisation de construire un lotissement sur les parcelles n° 108 et 364p de la section cadastrale AH de la commune de Bernières-sur-Mer, une opération de diagnostic archéologique a été confiée à l’INRAP en préalable à la réalisation de ce projet. Ce dernier concerne une surface de 54 500 m2 située au nord-est de la commune, et accolée à une parcelle dans laquelle bon nombre de ves..