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Introduction
Current institution
Additional affiliations
January 2014 - October 2015
January 2009 - February 2015
January 2003 - December 2009
Education
June 2010 - February 2011
October 1993 - June 1996
October 1989 - October 1992
Publications
Publications (114)
We have developed a cell-centered Finite Volume discretization of the so-called Wilkins hypoelastic
model written under Lagrangian formalism [1]. In this framework, standard infinitesimal elastoplasticity
models are extended to the finite strain range by formulating constitutive law in terms of frame invariant
stress rates. In spite of its simplici...
We present a finite volume based cell-centered method for solving diffusion equations on three-dimensional unstructured grids with general tensor conduction. Our main motivation concerns the numerical simulation of the coupling between fluid flows and heat transfers. The corresponding numerical scheme is characterized by cell-centered unknowns and...
In this paper, we describe a cell-centered Lagrangian scheme devoted to the numerical simulation of solid dynamics on two-dimensional unstructured grids in planar geometry. This numerical method, utilizes the classical elastic-perfectly plastic material model initially proposed by Wilkins [M.L. Wilkins, Calculation of elastic–plastic flow, Meth. Co...
In this paper, we describe a second-order accurate cell-centered finite volume method for solving anisotropic diffusion on two-dimensional unstructured grids. The resulting numerical scheme, named CCLAD (Cell-Centered LAgrangian Diffusion), is characterized by a local stencil and cell-centered unknowns. It is devoted to the resolution of diffusion...
Instead of ensuring that fluxes across edges add up to zero, we split the edge in two halves and also associate different fluxes to each of its sides. This is possible due to non-standard Riemann solvers with free parameters. We then enforce conservation by making sure that the fluxes around a node sum up to zero, which fixes the value of the free...
Instead of ensuring that fluxes across edges add up to zero, we split the edge in two halves and also associate different fluxes to each of its sides. This is possible due to non-standard Riemann solvers with free parameters. We then enforce conservation by making sure that the fluxes around a node sum up to zero, which fixes the value of the free...
We construct an unconventional divergence preserving discretization of updated Lagrangian ideal magnetohydrodynamics (MHD) over simplicial grids. The cell-centered finite-volume (FV) method employed to discretize the conservation laws of volume, momentum, and total energy is rigorously the same as the one developed to simulate hyperelasticity equat...
The equations of Lagrangian gas dynamics fall into the larger class of overdetermined hyperbolic and thermodynamically compatible (HTC) systems of partial differential equations. They satisfy an entropy inequality (second principle of thermodynamics) and conserve total energy (first principle of thermodynamics). The aim of this work is to construct...
This paper describes a novel subface flux-based Finite Volume (FV) method for discretizing multi-dimensional hyperbolic systems of conservation laws of general unstructured grids. The subface flux numerical approximation relies on the notion of simple Eulerian Riemann solver introduced in the seminal work [G. Gallice; Positive and entropy stable Go...
In this paper, we present a conservative cell-centered Lagrangian Finite Volume scheme for solving the hyperelasticity equations on unstructured multidimensional grids. The starting point of the present approach is the cell-centered FV discretization named EUCCLHYD and introduced in the context of Lagrangian hydrodynamics. Here, it is combined with...
This talk presents the development of FV methods to solve the non-viscous and non-conductive part of the N-S equations, i.e. the two-dimensional Euler equations. It focuses on unstructured meshes and use the Lagrangian framework as a stepping stone to derive an approximate RS in the Eulerian framework. On the ground of this, direct estimations of o...
In this paper we propose to revisit the notion of simple Riemann solver in Lagrangian coordinates follow- ing Gallice ”Positive and entropy stable godunov-type schemes for gas dynamics and MHD equations in Lagrangian or Eulerian coordinates” in Numer. Math., 94, 2003. We interpret and supplement this work with an advanced study on the notions of wa...
In this paper we present a conservative cell-centered Lagrangian finite volume scheme for the solution of the hyper-elasticity equations on unstructured multidimensional grids. The starting point of the new method is the Eucclhyd scheme, which is here combined with the a posteriori Multidimensional Optimal Order Detection (MOOD) limiting strategy t...
This paper describes a novel subface flux-based Finite Volume (FV) method for discretizing multi-dimensional hyperbolic systems of conservation laws of general unstructured grids. The subface flux numerical approximation relies on the notion of simple Eulerian Riemann solver introduced in the seminal work [G. Gallice; Positive and entropy stable Go...
This paper deals with the Finite Volume discretization of a non linear diffusion equation with non source terms. This equation is of degenerate parabolic type. It describes the transport of turbulent kinetic energy in the more general framework of a turbulence model with a single equation. A specific analytic solution with compact support of this n...
The extension of the 3D cell-centered Finite Volume EUCCLHYD scheme to the hyperelasticity system is proposed here. This study is based on the left Cauchy-Green tensor B which enables to work in a fully updated Lagrangian formalism. The second order extension of this scheme is proposed using a MUSCL (Monotonic Upstream-centered Scheme for Conservat...
It is well known that gas dynamics equations may develop singularities,i.e., shock waves, at a finite time. The related discontinuous solutions are thus sought under a weak form which corresponds to the integral form of the underlying conservation laws of mass, momentum and total energy. Weak solutions being not uniquely defined, the physically rel...
The extension of the 3D cell-centered Finite Volume EUCCLHYD scheme to the hyperelasticity system is proposed here. This study is based on the left Cauchy-Green tensor B instead of the deformation gradient F which enables to work in a fully updated Lagrangian formalism. The second order extension of this scheme is proposed using a MUSCL procedure c...
High Energy Density Physics (HEDP) flows are multi-material flows characterized by strong shock waves and large changes in the domain shape due to rarefaction waves. Numerical schemes based on the Lagrangian formalism are good candidates to model this kind of flows since the computational grid follows the fluid motion. This provides accurate result...
In this paper we develop a conservative cell-centered Lagrangian finite volume scheme for the solution of the hydrodynamics equations on unstructured multidimensional grids. The method is derived from the Eucclhyd scheme discussed in [47,43,45. It is second-order accurate in space and is combined with the a posteriori Multidimensional Optimal Order...
The formation and the interaction of multiple cavities, induced by tightly focused femtosecond laser pulses, are studied by using a developed numerical tool, including the thermo-elasto-plastic material response. Simulations are performed in fused silica in cases of one, two, and four spots of laser energy deposition. The relaxation of the heated m...
The formation and the interaction of multiple cavities, induced by tightly focused femtosecond laser pulses, are studied by using a developed numerical tool, including the thermo-elasto-plastic material response. Simulations are performed in fused silica in cases of one, two, and four spots of laser energy deposition. The relaxation of the heated m...
The absorbed laser energy of a femtosecond laser pulse in a transparent material induces a warm dense matter region which relaxation may lead to structural modifications in the surrounding cold matter. The modeling of the thermo-elasto-plastic material response is addressed to predict such modifications. It has been developed in a 2D plane geometry...
The absorbed laser energy of a femtosecond laser pulse in a transparent material induces a warm dense matter region which relaxation may lead to structural modifications in the surrounding cold matter. The modeling of the thermo-elasto-plastic material response is addressed to predict such modifications. It has been developed in a 2D plane geometry...
In the context of High Energy Density Physics and more precisely in the field of laser plasma interaction, Lagrangian schemes are commonly used. The lack of robustness due to strong grid deformations requires the regularization of the mesh through the use of Arbitrary Lagrangian Eulerian methods. Theses methods usually add some diffusion and a loss...
The Finite Volume discretization of non-linear elasticity equations seems to be a promising alternative to the traditional Finite Element discretization as mentioned by Lee et al. [Computers and Structures (2013)]. In this work, we propose to solve the elastic response of a solid material by using a cell-centered Finite Volume Lagrangian scheme in...
This paper reviews recent developments in Arbitrary Lagrangian Eulerian (ALE) methods for modeling high speed compressible multimaterial flows in complex geometry on general polygonal meshes. We only consider the indirect ALE approach which consists of three key stages: a Lagrangian stage, in which the solution and the computational mesh are update...
We present the two main types of Finite Volume Lagrangian schemes named: staggered-grid hydrodynamics (SGH) and colocated Lagrangian hydrodynamics (CLH). Both are devoted to solve the hydrodynamic conservation laws and extended system in multidimension on general grid. They are funded on common paradigms, such as the need to solve the conservation...
One of the main issues in the field of numerical schemes is to ally robustness with accuracy. Considering gas dynamics, numerical approximations may generate negative density or pressure, which may lead to nonlinear instability and crash of the code. This phenomenon is even more critical using a Lagrangian formalism, the grid moving and being defor...
This paper is the second part of a series of two. It follows the part I, in which the positivity-preservation property of methods solving one-dimensional Lagrangian gas dynamics equations, from first-order to high-orders of accuracy, was addressed. This article aims at extending this analysis to the two-dimensional case. This study is performed on...
Solving the gas dynamics equations under the Lagrangian formalism enables to simulate complex flows with strong shock waves. This formulation is well suited to the simulation of multi-material compressible fluid flows such as those encountered in the domain of High Energy Density Physics (HEDP). These types of flows are characterized by complex 3D...
One of the main issues in the field of numerical schemes is to ally robustness with accuracy. Considering gas dynamics, numerical approximations may generate negative density or pressure, which may lead to nonlinear instability and crash of the code. This phenomenon is even more critical using a Lagrangian formalism, the grid moving and being defor...
The numerical simulation of the response of solid materials undergoing large strains is of particular
interest in many industrial applications such as high-velocity impacts [3]. In this presentation, we shall
describe a cell-centered Lagrangian scheme devoted to the numerical simulation of solid dynamics on
two-dimensional unstructured grids. This...
We use here a reconnection ALE (ReALE) strategy to solve hydrodynamic compressible flows in cylindrical geometries. The main difference between the classical ALE and the ReALE method is the rezoning step where we allow change in the topology. This leads for ReALE to a polygonal mesh, which follows more efficiently the flow. We present here a new di...
Based on the total Lagrangian kinematical description, a discontinuous Galerkin (DG) discretization of the gas dynamics equations is developed for two-dimensional fluid flows on general unstructured grids. Contrary to the updated Lagrangian formulation, which refers to the current moving configuration of the flow, the total Lagrangian formulation r...
Hydrodynamic instabilities play an important role in the target compression for inertial confine-ment fusion (ICF). We present the analytical solution of a perturbed isentropic implosion. We compare the analytical solution to the results obtained with perturbation and 2D Lagrangian hydrodynamic codes. We also compare results from 2D code and pertur...
This paper is devoted to the simulation of two-dimensional compressible fluid flows. We present a new second-order cell-centered scheme that solves the gas dynamics equations written in the Lagrangian formalism. The scheme is developed on general unstructured meshes consisting of arbitrary polygons. The robustness and accuracy of this new scheme ar...
This work presents a multi-dimensional cell-centered unstructured finite volume scheme for the solution of multimaterial compressible fluid flows written in the Lagrangian formalism. This formulation is considered in the Arbitrary-Lagrangian–Eulerian (ALE) framework with the constraint that the mesh velocity and the fluid velocity coincide. The lin...
We propose a new cell-centered diffusion scheme on unstructured meshes. The main feature of this scheme lies in the introduction of two normal fluxes and two temperatures on each edge. A local variational formulation written for each corner cell provides the discretization of the normal fluxes. This discretization yields a linear relation between t...
SUMMARYA complete reconnection‐based arbitrary Lagrangian–Eulerian (ReALE) strategy devoted to the computation of hydrodynamic applications for compressible fluid flows is presented here. In ReALE, we replace the rezoning phase of classical ALE method by a rezoning where we allow the connectivity between cells of the mesh to change. This leads to a...
SUMMARY The aim of the present work is the 3D extension of a general formalism to derive a staggered discretization for Lagrangian hydrodynamics on unstructured grids. The classical compatible discretization is used; namely, momentum equation is discretized using the fundamental concept of subcell forces. Specific internal energy equation is obtain...
We present a comparison of a classical arbitrary Lagrangian-Eulerian (ALE) method with a new multi-material reconnection-based arbitrary-Lagrangian-Eulerian (Re-ALE) strategy devoted to the computation of multi-material compressible fluid flows using the Moment Of Fluid (MOF) interface reconstruction. In ReALE we replace the rezoning phase of class...
A complete reconnection-based arbitrary-Lagrangian-Eulerian (ReALE) strategy devoted to the computation of hydrodynamic applications for compressible fluid flows is presented here. In ReALE we replace the rezoning phase of classical ALE method by a rezoning where we allow the connectivity between cells of the mesh to change. This leads to a polygon...
In this paper we present recent developments concerning a Cell-Centered
Arbitrary Lagrangian Eulerian (CCALE) strategy using the Moment Of Fluid (MOF)
interface reconstruction for the numerical simulation of multi-material
compressible fluid flows on general unstructured grids in cylindrical
geometries. Especially, our attention is focused here on...
The aim of the present work is to develop a general formalism to derive staggered discretizations for Lagrangian hydrodynamics on two-dimensional unstructured grids. To this end,wemake use of the compatible discretization that has been initially introduced by E. J. Caramana et al., in J. Comput. Phys., 146 (1998). Namely, momentum equation is discr...
We present a new hybrid conservative remapping algorithm for multimaterial Arbitrary Lagrangian–Eulerian (ALE) methods. The hybrid remapping is performed in two steps. In the first step, only nodes of the grid that lie inside subdomains occupied by single materials are moved. At this stage, computationally cheap swept-region remapping is used. In t...
We present cell-centered discontinuous Galerkin discretizations for two-dimensional scalar conservation laws on unstructured grids and also for the one-dimensional Lagrangian hydrodynamics up to third-order. We also demonstrate that a proper choice of the numerical fluxes allows to enforce stability properties of our discretizations.
We present an original Cell-Centered Arbitrary Lagrangian–Eulerian (CCALE) strategy using the Moment Of Fluid (MOF) interface reconstruction devoted to the numerical simulation of two-dimensional multi-material compressible fluid flows on general unstructured grids. Our methodology is assessed through several demanding two-dimensional tests and com...
We present a complete Arbitrary Lagrangian Eulerian (ALE) strategy devoted to the computation of multi-material fluid flows using the volume of fluid (VOF) interface reconstruction method applied to plasma physics and inertial confinement fusion (ICF). The interface tracking is coupled to a two-temperature hydrodynamics model in the framework of a...
New method for weighted condition number smoothing of general unstructured computational meshes is presented. Its core, proper discretization of weighted smoothness functional, is detailed, options of particular implementation are discussed and demonstrated on general convex polygonal cells in two dimensions. Possible applications of this algorithm...
Remapping is one of the essential parts of most arbitrary Lagrangian–Eulerian (ALE) methods. In this short paper we focus on multi-material fluid flows. We present a hybrid remapping method combining the swept remapping algorithm in pure regions with the intersection-based remapping algorithm close to material interfaces. We describe the hybrid rem...
We present a one-step high-order cell-centered numerical scheme for solving Lagrangian hydrodynamics equations on unstructured grids. The underlying finite volume discretization is constructed through the use of the sub-cell force concept invoking conservation and thermodynamic consistency. The high-order extension is performed using a one-step dis...
This paper deals with the extension to the cylindrical geometry of the recently introduced Reconnection algorithm for Arbitrary-Lagrangian–Eulerian (ReALE) framework. The main elements in standard ALE methods are an explicit Lagrangian phase, a rezoning phase, and a remapping phase. Usually the new mesh provided by the rezone phase is obtained by m...
We develop a general formalism to derive cell-centered Lagrangian scheme, wherein numerical fluxes are expressed in terms of sub-cell force. The general form of the sub-cell force is obtained by requiring the scheme to satisfy a semi-discrete entropy inequality. Sub-cell force and nodal velocity are computed consistently with cell volume variation...
We present an original and accurate cell-centered ALE (arbitrary Lagrangian–Eulerian) algorithm devoted to the simulation of multi-material fluid flows using VOF (Volume Of Fluid) interface reconstruction. Copyright © 2010 John Wiley & Sons, Ltd.
With the ongoing development of high energy laser facilities designed to achieve inertial confinement fusion, the ability to simulate debris ejection from metallic shells subjected to intense laser irradiation has become a key issue. We present an experimental and numerical study of fragmentation processes generating high velocity ejecta from laser...
The purpose of this document is to present some of the works undertaken at CELIA laboratory (CEA,
CNRS, Université Bordeaux I) in the field of numerical modeling of highly compressible fluid flows.
This activity within the team Interaction-Inertial Confinement Fusion-Astrophysics, had as main
objective the development of robust numerical schemes de...
This presentation summarizes the works done at CELIA Laboratory during the period 2003-2009 and dedicated to the numerical simulation of High Energy Density Physics. These works rely on the development of Co-Located Cell Centered Lagrangian Hydrodynamics.
In this paper, complementary techniques are combined to investigate
dynamic fragmentation and shrapnel generation in laser shock-loaded
samples of aluminium and gold, which will be two constituents of the
target assemblies designed for the inertial confinement fusion (ICF)
experiments to be performed on large scale laser facilities such as the
Nati...
Dynamic fragmentation of shock-loaded metals is an issue of considerable importance for both basic science and a variety of technological applications, such as inertial confinement fusion, which involves high energy laser irradiation of thin metallic shells. In this context, we present an experimental and numerical study of debris ejection in laser...
We present a new cell-centered multi-material arbitrary Lagrangian–Eulerian (ALE) scheme to solve the compressible gas dynamics equations on two-dimensional unstructured grid. Our ALE method is of the explicit time-marching Lagrange plus remap type. Namely, it involves the following three phases: a Lagrangian phase wherein the flow is advanced usin...
In this work we develop a general framework to derive and analyze staggered numerical scheme devoted to solve hydrodynamics equations.
We present a new reconnection-based arbitrary-Lagrangian–Eulerian (ALE) method. The main elements in a standard ALE simulation are an explicit Lagrangian phase in which the solution and grid are updated, a rezoning phase in which a new grid is defined, and a remapping phase in which the Lagrangian solution is transferred (conservatively interpolate...
This workshop follows on from the successful first one held in San Diego during the SIAM Annual Meeting 2008. It provides a forum for exploring the new trends in numerical methods devoted to the simulation of multi-material compressible fluid flows.
We present a general sub-cell force-based formalism to derive cell-centered schemes for two-dimensional Lagrangian hydrodynamics on unstructured grids. For a general polygonal grid, the discrete equations that govern the time rate of change of volume, momentum and total energy are obtained by means of a control volume formulation of the gas dynamic...
We develop a general framework to derive and analyze staggered numerical schemes devoted to solve hydrodynamics equations in 2D. In this framework a cell-centered multi-dimensional approximate Riemann solver is used to build a form of artificial viscosity that leads to a conservative, compatible and thermodynamically consistent scheme. A second ord...
We present a new hybrid remapping (conservative interpolation) algorithm for multimaterial Arbi- trary Lagrangian-Eulerian (ALE) methods. The hybrid remapping is performed in two steps. In the rst step, only nodes of the grid that lie inside subdomains occupied by single materials are moved. At this stage, computationally cheap swept-region remappi...
The goal of this paper is to present high-order cell-centered schemes for solving the equations of Lagrangian gas dynamics written in cylindrical geometry. A node-based discretization of the numerical fluxes is obtained through the computation of the time rate of change of the cell volume. It allows to derive finite volume numerical schemes that ar...
The European High Power laser Energy Research (HiPER) project aims at demonstrating the feasibility of high gain inertial
confinement fusion (ICF) using the fast ignitor approach. A baseline target has been recently developed by Atzeni et al. [Phys.
Plasmas 14, 052702 (2007)]. The radiative transport have a minor effect on the peak areal density bu...
Recently, a European collaboration has proposed the High Power Laser Energy Research (HiPER) facility, with the primary goal of demonstrating laser driven inertial fusion fast ignition. HiPER is expected to provide 250 kJ in multiple, 3ω (wavelength λ = 0.35 µm), nanosecond beams for compression and 70 kJ in 10–20 ps, 2ω beams for ignition. The bas...
We present a high-order cell-centered Lagrangian scheme for solving the two-dimensional gas dynamics equations on unstructured meshes. A node-based discretization of the numerical fluxes for the physical conservation laws allows to derive a scheme that is compatible with the geometric conservation law (GCL). Fluxes are computed using a nodal solver...
Hydrodynamics and robustness of three high yield targets within the HiPER project are presented. Using realistic illumination nonuniformity configuration, hydrodynamic perturbations sensitivity analysis is carried out. A rather simple hydrodynamic perturbation modeling sequence is validated thanks to 2D simulations. 1D simulations post-processed wi...
The Ligne d'Integration Laser (LIL) facility has been designed as a prototype for the Laser MegaJoule (LMJ) which is a cornerstone of the French 'Simulation Program'. This laser has been intensively used to test and improve the LMJ components. In addition, a large panel of plasma diagnostics has been installed and is currently used to perform laser...
In laser produced plasmas large self-generated magnetic fields have been measured. The classical formulas by Braginskii predict that magnetic fields induce a reduction of the magnitude of the heat flux and its rotation through the Righi-Leduc effect. In this paper a second order tensorial diffusion method used to correctly solve the Righi-Leduc eff...
We present an original and accurate unstructured cell-centred arbitrary Lagrangian–Eulerian algorithm devoted to the simulation of multi-material fluid flows. Copyright © 2007 John Wiley & Sons, Ltd.
This paper is devoted to the simulation of two-dimensional compressible fluid flows. We present a new second-order cell-centered scheme that solves the gas dynamics equations written in the Lagrangian formalism. The scheme is developed on general unstructured meshes consisting of arbitrary polygons. The robustness and accuracy of this new scheme ar...
The European High Power laser Energy Research (HiPER) project aims at demonstrating the feasibility of high gain inertial confinement fusion using the fast ignitor approach. A baseline target has been recently developed by Atzeni et al (2007 Phys. Plasmas 14 052702). We study here the robustness of this target during the compression phase and defin...
