EUROPLEXUS is a computer code being jointly developed since 1999 by CEA (CEN Saclay, DMT) and EC (JRC Ispra, IPSC) under a collaboration contract. It stems from CEA’s CASTEM-PLEXUS (a program belonging to the CASTEM system) and the previous CEA- EC joint product PLEXIS-3C. The code analyses 1-D, 2-D or 3-D domains composed of solids (continua, shells or beams) and fluids. Fluid-structure interaction is also taken into account. The program uses an explicit algorithm (central-difference) for the discretization in time and therefore it is best adapted to rapid dynamic phenomena (fast transient dynamics) such as explosions, impacts, crashes etc. Geometric non linearity (large displacements, large rotations, large strains), and the non-linearity of materials (plasticity, viscoplasticity, etc) are fully taken into account. The spatial discretization is mainly based on the Finite Element or Finite Volume method. Other formulations such as SPH (Smoothed Particle Hydrodynamics), Spectral ELements, Dif- fuse Elements etc. are also available or under development. Numerous element types and a comprehensive library of material types for solids, fluid and special media (e.g. impedances) are available. Three main descriptions are available in the code: the Lagrangian description which is well suited for the structural domain, the Eulerian description useful for purely fluid problems, and the Arbitrary Lagrangian Eulerian (ALE) description which is typically used in fluid-structure interaction problems. EUROPLEXUS is interfaced to various pre- and post-processing programs that enable the meshing of the studied domain (e.g. CEA’s Cast3m) and the visualization of the results (e.g. Cast3m, ParaView or EUROPLEXUS itself). Different types of licenses are available of EUROPLEXUS. A limited version of the code can be downloaded. For research and education these licenses are mainly for free. Details can be found on the web page of EUROPLEXUS (http://www-epx.cea.fr/). This User’s manual is updated daily and can be downloaded from http://europlexus.jrc.ec.europa.eu/. A large bibliography concerning EUROPLEXUS as well as its ancestors is provided at the end of the present manual (see Section BIB). Many of the cited documents are available to EUROPLEXUS developers in electronic form on the EUROPLEXUS Consortium web site (https://europlexus.jrc.ec.europa.eu/).

A Finite-Volume scheme for the numerical computations of compressible single- and two-phase flows in flexible pipelines is proposed based on an approximate Godunov-type approach. The spatial discretization is here obtained using the HLLC scheme. In addition, the numerical treatment of abrupt changes in area and network including several pipelines connected at junctions is also considered. The proposed approach is based on the integral form of the governing equations making it possible to tackle general equations of state. A coupled approach for the resolution of fluid-structure interaction of compressible fluid flowing in flexible pipes is considered. The structural problem is solved using Euler-Bernoulli beam finite elements. The present Finite-Volume method is applied to ideal gas and two-phase steam-water based on the Homogeneous Equilibrium Model (HEM) in conjunction with a tabulated equation of state in order to demonstrate its ability to tackle general equations of state. The extensive application of the scheme for both shock tube and other transient flow problems demonstrates its capability to resolve such problems accurately and robustly. Finally, the proposed 1-D fluid-structure interaction model appears to be computationally efficient. Share Link : https://authors.elsevier.com/c/1Wlfs508HeRWN

The method presented below focuses on the numerical approximation of the Euler compressible system. It pursues a two-fold objective: being able to accurately follow slow material waves as well as strong shock waves in the context of low Mach number flows. The resulting implicit–explicit(IMEX) fractional step approach leans on a dynamic splitting designed to react to the time fluctuations of the maximal flow Mach number. When the latter rises suddenly, the IMEX scheme, so far driven by a material-wave Courant number, turn into a time-explicit approximate Riemann solver constrained by an acoustic-wave Courant number. It is also possible to enrich the dynamic splitting in order to capture high pressure jumps even when the flow Mach number is low. One-dimensional low Mach number test cases involving single or multiple waves confirm that the present approach is as accurate and efficient as an IMEX Lagrange-Projection method. Besides, numerical results suggest that the stability of the present method holds for any Mach number if the Courant number related to the convective subsystem arising from the splitting is of order unity.

Herein, a Mach-sensitive fractional step approach is proposed for Euler-like systems. The key idea is to introduce a time-dependent splitting which dynamically decouples convection from acoustic phenomenon following the fluctuations of the flow Mach number. By doing so, one seeks to maintain the accuracy of the computed solution for all Mach number regimes. Indeed, when the Mach number takes high values, a time-explicit resolution of the overall Euler-like system is entirely performed in one of the present splitting step. On the contrary, in the low-Mach number case, convection is totally separated from the acoustic waves production. Then, by performing an appropriate low-Mach correction on the acoustic step of the splitting, the numerical diffusion can be significantly reduced. A study made on both convective and acoustic subsystems of the present approach has revealed some key properties as hyperbolicity and positivity of the density and internal energy in the case of an ideal gas thermodynamics. The one-dimensional results made on a wide range of Mach numbers using an ideal and a stiffened gas thermodynamics show that the present approach is as accurate and CPU-consuming as a state of the art Lagrange-Projection-type method.

This paper is devoted to the computation of the fast depressurization of water using a two-fluid model. Such application, which is extensively studied in the nuclear field, involves many interactions between two phenomena, the mass transfer and the propagation of pressure waves. A simple but physically-based modelling of the mass transfer for the depressurization of water is proposed, which relies on the work of Bilicki & Kestin [1] in the homogeneous frame. Four different experiments have been chosen to assess the proposed model. Three of them study the depressurization of hot water in a pressurized pipe. The comparison between converged numerical results and the experimental data shows a good agreement and demonstrates the ability of the two-fluid-model to capture the proper mass transfer for a wide range of thermodynamical conditions. The last test-case is the HDR experiment which considers the depressurization of a full-scale vessel under the hypothesis of a Loss Of Coolant Accident. The results of an ALE computation show the ability of the proposed model to retrieve experimental data in both structure and fluid.