Nantes, France


Nantes, France
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Agency: European Commission | Branch: H2020 | Program: RIA | Phase: MG-3.1-2016 | Award Amount: 6.64M | Year: 2016

SARAH is concerned with establishing novel holistic, simulation-based approaches to the analysis of aircraft ditching. It is build up from a consortium of experts from OEM industries, experienced suppliers of simulation technologies, established research institutions and representatives of the certification authorities. Results of SARAH are expected to support a performance-based regulation and certification for next generation aircraft and helicopter and to enhance the safe air transport as well as to foster the trustworthiness of aviation services. Aircrafts and helicopters often travel above water and thus have to prove a safe landing under emergency conditions. The specific challenge is to minimize the risk of injury to passengers and to enable safe evacuation. Accordingly, the motion of the aircraft/helicopter along with the forces acting on the structure are studied for controlled water impact during the design phase of an aircraft. Ditching has close links with crash simulation, but also distinctive features. Examples refer to hydrodynamic slamming loads on airborne vehicles and complex hydromechanics (partially at very large forward speeds) as well as the interaction of multi-phase fluid dynamics (involving air, water, and vapor phases) and structure mechanics. Design for ditching involves more than the analysis of loads and subsequent strengthening of the structure. It often requires adjustment campaigns for the handling of the vehicle during approach and the identification of favorable approach/flight-path conditions in line with the pilots flying capabilities to minimize the remaining kinetic energy of the vehicle to be transferred into the water. In conclusion, a pressing need for more advanced studies to support the development of next-generation, generalized simulation-based ditching-analysis practices is acknowledged by all stakeholders. The public interest in safety makes this proposal an ideal candidate for a European research proposal.

Agency: European Commission | Branch: H2020 | Program: RIA | Phase: MG-6.2-2014 | Award Amount: 7.55M | Year: 2015

SYNCHRO-NET will demonstrate how a powerful and innovative SYNCHRO-modal supply chain eco-NET can catalyse the uptake of the slow steaming concept and synchro-modality, guaranteeing cost-effective robust solutions that de-stress the supply chain to reduce emissions and costs for logistics operations while simultaneously increasing reliability and service levels for logistics users. The core of the SYNCHRO-NET solution will be an integrated optimisation and simulation eco-net, incorporating: real-time synchro-modal logistics optimisation (e-Freight-enabled); slow steaming ship simulation & control systems; synchro-modal risk/benefit analysis statistical modelling; dynamic stakeholder impact assessment solution; and a synchro-operability communications and governance architecture. Perhaps the most important output of SYNCHRO-NET will be the demonstration that slow steaming, coupled with synchro-modal logistics optimisation delivers amazing benefits to all stakeholders in the supply chain: massive reduction in emissions for shipping and land-based transport due to modal shift to greener modes AND optimised planning processes leading to reduced empty kms for trucks and fewer wasted repositioning movements. This will lead to lower costs for ALL stakeholders shipping companies and logistics operators will benefit from massive reduction in fuel usage, faster turnaround times in ports & terminals and increased resource utilisation/efficiency. Customers and end users will have greater control of their supply chain, leading to more reliable replenishment activity and therefore reduced safety stocks and expensive warehousing. Authorities and governmental organisations will benefit from a smoother, more controlled flow of goods through busy terminals, and reduction of congestion on major roads, thus maximising the utilisation of current infrastructure and making the resourcing of vital activities such as import/export control, policing and border security less costly.

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.

Oger G.,École Centrale Nantes | Marrone S.,CNR Italian Ship Model Basin | Le Touze D.,École 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.

Maruzewski P.,Ecole Polytechnique Federale de Lausanne | Le Touze D.,École 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.

Fourey G.,École Centrale Nantes | Oger G.,HydrOcean | Le Touze D.,École Centrale Nantes | Alessandrini B.,École Centrale Nantes
IOP Conference Series: Materials Science and Engineering | Year: 2014

The Smoothed Particle Hydrodynamics (SPH) method presents different key assets for modelling violent Fluid-Structure Interactions (FSI). First, this method is a meshless method, which drastically reduces the complexity of handling the fluid-structure interface when using SPH to model the fluid and coupling it with a Finite Element Method (FEM) for the solid. Second, the method is Lagrangian and large deformations of the fluid domain can thus be followed, which is especially interesting for simulating violent interactions in presence of a free surface, or which induce large deformations, rotations, and translations of the solid. Third, the SPH method being explicit, the time scale of the SPH resolution in the fluid domain is naturally adapted to the FEM resolution in the solid. Free-surface FSIs can also be simulated without including the air phase when it does not play a significative role. For violent interactions where the fluid compressibility matters, it is also intrinsically modelled by the SPH method. The paper details the SPH method used and the coupling. The FEM solver is a standard open source solver for solid mechanics. Validation test cases are then presented in detail. They include the hydrodynamic impact of elastic wedges at high speed, where local pressures and wedge deformations are compared to experimental data. © 2010 IOP Publishing Ltd.

Brosset L.,Gaztransport and Technigaz | Ghidaglia J.-M.,Ecole Normale Superieure de Cachan | Guilcher P.-M.,HydrOcean | Tarnec L.L.,Ecole Normale Superieure de Cachan
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2013

Recent experimental (Lafeber et al., 2012b) and numerical (Bredmose et al. (2008), Guilcher et al. (2012)) studies showed that the behaviour of gas pockets entrapped by a breaking wave when impacting a wall is well described by the piston model first modelized with a single Ordinary Differential Equation (ODE) by Bagnold under the assumption of a perfect gas and isentropic conditions (Bagnold, 1939). In Bagnold's original work, the solid piston was only animated by an initial velocity. A dimensionless form of the piston dynamics was proposed. Therefore, the problem depended only on two dimensionless numbers: The isentropic constant of the gas γ̃g and Bagnold number S̃g. As for a sloshing impact inside the tank of LNG vessels, an inertial acceleration is always involved during the impacts and as several authors observed some evidence of the influence of liquid compressibility during wave impact tests (Brosset et al., 2011) or simulations of such tests (Bredmose et al., 2009), a 1D model of the liquid piston problem including a constant inertial acceleration is proposed based on isentropic compressible Euler equations, as an extension of the previous 0D model. A dimensionless form of the equations is proposed relying on six dimensionless numbers, including the initial Bagnold number, Froude number and the dimensionless compressibility index of the liquid. From this model can be derived a 0D model of the solid piston problem assuming that the liquid is incompressible and the density is constant into the gas. It simplifies to the initial Bagnold model when considering no acceleration. Two different computing programs have been developed separately by ENS-Cachan/Eurobios and by HydrOcean based on the general 1D model, giving equivalent results. A parametric study is performed with the first one looking at the influence of each dimensionless number on the maximum pressure at wall. Three different regimes are observed, each of them governed by a restricted list of dimensionless numbers. A phenomenological study is performed with the second program looking in depth to the physics involved in the three different regimes. The relevance of the model for applications to real gas pocket wave impacts is discussed. The scaling of the 1D liquid piston model is studied giving insight on the scaling process when several similarity laws are at work. Copyright © 2013 by the International Society of Offshore and Polar Engineers (ISOPE).

Guilcher P.M.,HydrOcean | Brosset L.,Gaztransport and Technigaz | Couty N.,HydrOcean | Le Touze D.,École 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).

Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: SST.2008.4.1.1. | Award Amount: 4.02M | Year: 2009

The increase in world trade has largely contributed to the explosion in sea traffic. As a result, the market demand is leading to Ultra Large Container Ships (ULCS), which have a capacity up to 14,000 TEU with length up to 400 m, without changes of the operational requirements (speed around 27 knots). The particular structural design of the container ships, leads to open midship sections, resulting in increased sensitivity to torsional and horizontal bending loads which is much more complex to model. At the same time, due to their large dimensions, the ULCS become much softer and their structural natural frequencies become significantly lower so that the global hydroelastic structural responses (springing & whipping) can become a critical issue in the ship design and should be properly modelled by the simulation tools. On the other hand, it appears that the existing simulation tools do not provide the definite answer to all these design issues and there is a clear need for their improvement. The particular importance of whipping and the insufficient knowledge in its modelling is clearly reflected in the recent MAIB (Marine Accident Investigation Branch) report, following the loss of theMSC Napoli container ship: It is likely that the hull of MSC Napoli was subjected to additional load due to whipping. it is apparent that whipping effect is currently very difficult to reliably calculate or model. In view of the potential increase in wave loading due to whipping effect, further research is required to ensure that the effect is adequately accounted for in ship design and structural analyses, and that sufficient allowance is made for the effect when determining design margins. The final goal of the project is to deliver clearly validated design tools and guidelines, capable of analysing all hydro-structure interaction problems relevant to ULCS.

Agency: European Commission | Branch: FP7 | Program: CP | Phase: ICT-2007.8.0 | Award Amount: 2.49M | Year: 2009

The objective of NextMuSE is to initiate a paradigm shift in the technology of Computational Fluid Dynamics (CFD) and Computational Multi-Mechanics (CMM) simulation software which is used to model physical processes in research and technology development across a range of industries. NextMuSE relies on a mesh-free method, Smoothed Particle Hydrodynamics (SPH), which is fundamentally different from conventional techniques and can overcome their shortcomings. The NextMuSE paradigm is defined by two characteristics: - accurate robust multi-mechanics modelling in applications where traditional methods fail (e.g. simultaneous fluid and solid mechanics in a ship under extreme wave loading). - an immersive, interactive user interface (ICARUS) to allow the user-engineer to manage and partially automate the extremely complex inputs and outputs of such multi-mechanics simulations. The objectives will be achieved through 7 work packages. 1: Key enhancements of core SPH algorithms. 2: Adapted physical modelling of fluids: turbulence, multiphase flow. 3: Modelling of fluid-structure interaction. 4: High-performance computing: highly efficient scalable algorithms for very large simulations. 5: Development of an immersive and highly visual simulation/design environment to interact with the technology. 6: Realistic representative applications in the marine, energy and biomedical industries. 7: Dissemination, communication and exploitation. This project will remove technology roadblocks and enable an enhanced and extended role for ICT and HPC in socio-economically important engineering RTD and innovation sectors (including energy, healthcare and transport). Although there are challenging scientific bottlenecks, risk is managed and minimised through the design of the work plan and the selection of the consortium. The risk is balanced by the potential reward for this project, which is a proof-of-concept for a paradigm shift which will open the way for advanced immersive HPC simulation tools, seamlessly integrated into the RTD process for the most challenging engineering problems.

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