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Nantes, France

Guilcher P.-M.,HydrOcean | Couty N.,HydrOcean | Brosset L.,Gaztransport and Technigaz | Le Touze D.,Ecole Centrale Nantes
International Journal of Offshore and Polar Engineering | Year: 2013

After years of efforts, HydrOcean and Ecole Centrale Nantes, supported by GTT, succeeded in the development of an SPH software gathering all functionalities for relevant simulations of sloshing impacts on membrane containment systems for LNG carriers. Based on Riemann solvers, SPH-Flow deals with two compressible fluids (liquid and gas) that interact with the impacted structure through a complete coupling. The liquid, the gas and the structure are modeled by different kinds of dedicated particles allowing sharp interfaces. An efficient parallelization scheme enables performing calculations with a sufficiently high density of particles to capture adequately the sharp impact pressure pulses. The development of the bi-fluid version led, in a first stage, to unstable solutions in the gaseous phase for pressures below the ullage pressure. This difficulty was presented at ISOPE-2010 and has been overcome since. Simulations of a unidirectional breaking wave impacting a rigid wall after propagating along a flume are presented in this paper. The physical phenomena involved in the last stage of the impacts are scrutinized and compared with experimental results from the Sloshel project. A comparison between calculated results at full scale and at scale 1:6 is proposed. Conclusions about scaling in the context of wave impacts are given. © The International Society of Offshore and Polar Engineers.


Guilcher P.M.,HydrOcean | Brosset L.,Gaztransport and Technigaz | Couty N.,HydrOcean | Le Touze D.,Ecole Centrale Nantes
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2012

After years of efforts (Deuff, 2007, Oger et al., 2009; Guilcher et al., 2010), HydrOcean and Ecole Centrale Nantes, supported by GTT, succeeded in the development of a SPH software gathering all functionalities for relevant simulations of sloshing impacts on membrane containment systems for LNG carriers. Based on Riemann solvers, SPH-Flow deals with two compressible fluids (liquid and gas) that interact with the impacted structure through a complete coupling. The liquid, the gas and the structure are modelled by different kinds of dedicated particles allowing sharp interfaces. An efficient parallelisation scheme enables to perform calculations with a sufficiently high density of particles to capture adequately the sharp impact pressure pulses. The development of the bi-fluid version led in a first stage to unstable solutions in the gaseous phase for pressures below the ullage pressure. This difficulty was presented in ISOPE 2010 (see Guilcher et al., 2010) and has been overcome since. Simulations of a unidirectional breaking wave impacting a rigid wall after propagating along a flume are presented in this paper. The physical phenomena involved in the last stage of the impacts are scrutinized and compared with experimental results from Sloshel project (see Lafeber et al., 2012b). A comparison between calculated results at full scale and at scale 1:6 is proposed. Conclusions about scaling in the context of wave impacts are given. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).


Oger G.,Ecole Centrale Nantes | Marrone S.,CNR Italian Ship Model Basin | Le Touze D.,Ecole Centrale Nantes | de Leffe M.,HydrOcean
Journal of Computational Physics | Year: 2016

This paper addresses the accuracy of the weakly-compressible SPH method. Interpolation defects due to the presence of anisotropic particle structures inherent to the Lagrangian character of the Smoothed Particle Hydrodynamics (SPH) method are highlighted. To avoid the appearance of these structures which are detrimental to the quality of the simulations, a specific transport velocity is introduced and its inclusion within an Arbitrary Lagrangian Eulerian (ALE) formalism is described. Unlike most of existing particle disordering/shifting methods, this formalism avoids the formation of these anisotropic structures while a full consistency with the original Euler or Navier-Stokes equations is maintained. The gain in accuracy, convergence and numerical diffusion of this formalism is shown and discussed through its application to various challenging test cases. © 2016 Elsevier Inc.


Barras G.,Directorate General of Armaments | Souli M.,Lille Laboratory of Mechanics | Aquelet N.,Livermore Software Technology Corporation | Couty N.,HydrOcean
Ocean Engineering | Year: 2012

The paper deals with numerical methodology to model and study the bubble dynamics produced by an underwater explosion when it occurs in infinite medium, i.e. no interaction with any surrounding obstacle as the free surface, the seabed or deformable structures (surface ship or submarine). Numerical simulation of this class of problems requires large mesh domain and long time scale. In order to reduce the computing time we use the bi-dimensional axisymmetric Multi-Material Arbitrary Lagrange Euler formulation developed by the authors. Comparisons with empirical and theoretical formula are performed in order to corroborate the numerical results. Particularly, the spatial convergence, the influence of the domain size and the boundary conditions are studied in order to propose a consistent methodology with the explosion bubble phenomena. © 2011 Elsevier Ltd. All rights reserved.


Maruzewski P.,Ecole Polytechnique Federale de Lausanne | Le Touze D.,Ecole Centrale Nantes | Oger G.,HydrOcean | Avellan F.,Ecole Polytechnique Federale de Lausanne
Journal of Hydraulic Research | Year: 2010

Numerical simulations of water entries based on a three-dimensional parallelized Smoothed Particle Hydrodynamics (SPH) model developed by Ecole Centrale Nantes are presented. The aim of the paper is to show how such SPH simulations of complex 3D problems involving a free surface can be performed on a super computer like the IBM Blue Gene/L with 8,192 cores of Ecole polytechnique federale de Lausanne. The present paper thus presents the different techniques which had to be included into the SPH model to make possible such simulations. Memory handling, in particular, is a quite subtle issue because of constraints due to the use of a variable-h scheme. These improvements made possible the simulation of test cases involving hundreds of million particles computed by using thousands of cores. Speedup and efficiency of these parallel calculations are studied. The model capabilities are illustrated in the paper for two water entry problems, firstly, on a simple test case involving a sphere impacting the free surface at high velocity; and secondly, on a complex 3D geometry involving a ship hull impacting the free surface in forced motion. Sensitivity to spatial resolution is investigated as well in the case of the sphere water entry, and the flow analysis is performed by comparing both experimental and theoretical reference results. © 2010 International Association of Hydraulic Engineering and Research.

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