CNRS Optimisation and Reliability in Structural Mechanics lab

Rouen, France

CNRS Optimisation and Reliability in Structural Mechanics lab

Rouen, France
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Teodorescu I.,Technical University of Civil Engineering Bucharest | Tapusi D.,Technical University of Civil Engineering Bucharest | Erbasu R.,Technical University of Civil Engineering Bucharest | Bastidas-Arteaga E.,University of Nantes | Aoues Y.,CNRS Optimisation and Reliability in Structural Mechanics lab
Energy Procedia | Year: 2017

The mechanical and physical properties of wood structural elements and of wood structures are strongly affected by the combination of humidity, temperature variation and biological attack. The aim of this study is to develop a design model able to estimate timber elements decay function of the exploitation climatic conditions (temperature and humidity). The deterioration program may be applied on any type of wood element and is indicating the necessity of increasing the cross section dimensions if and when the specific humidity and temperature become of significant influence. The results of this study are of great importance as the behavior of a non-treated timber element can be surveyed when directly influenced by changes in climatic conditions (relative humidity and temperature). © 2017 The Authors.


Mycek P.,Duke University | Pinon G.,CNRS Laboratory of Waves and Complex Media | Lothode C.,CNRS Optimisation and Reliability in Structural Mechanics lab | Dezotti A.,University of Liverpool | And 2 more authors.
Applied Mathematical Modelling | Year: 2017

This paper presents a numerical investigation for the computation of wind or marine current turbines in a farm. A 3D unsteady Lagrangian vortex method is used together with a panel method in order to take into account for the turbines. In order to enforce the boundary condition onto the panel elements, a linear matrix system is defined. Solving general linear matrix systems is a topic with important scientific literature. But the main concern here is the application to a dedicated matrix which is non-sparse, non-symmetric, neither diagonally dominant nor positive-definite. Several iterative approaches were tested and compared. But after some numerical tests, a Bi-CGSTAB method was finally chosen. The main advantage of the presented method is the use of a specific preconditioner well suited for the desired application. The chosen implementation proved to be very efficient with only 3 iterations of our preconditioned Bi-CGSTAB algorithm whatever the turbine geometrical configuration. Although developed for wind or marine turbines, the proposed algorithm is absolutely not restricted to these cases, and can be applied to many others. At the end of the paper, some applications (specifically, wake computations) in a farm are presented, along with a quantitative assessment of the computational time savings brought by the iterative approach. © 2016


Mycek P.,CNRS Laboratory of Waves and Complex Media | Mycek P.,French Research Institute for Exploitation of the Sea | Gaurier B.,French Research Institute for Exploitation of the Sea | Germain G.,French Research Institute for Exploitation of the Sea | And 3 more authors.
International Journal of Marine Energy | Year: 2013

The understanding of interaction effects between marine energy converters represents the next step in the research process that should eventually lead to the deployment of such devices. Although some a priori considerations have been suggested recently, very few real condition studies have been carried out concerning this issue. Trials were run on 1/30th scale models of three-bladed marine current turbine prototypes in a flume tank. The present work focuses on the case where a turbine is placed at different locations in the wake of a first one. The interaction effects in terms of performance and wake of the second turbine are examined and compared to the results obtained on the case of one single turbine. Besides, a three-dimensional software, based on a vortex method is currently being developed, and will be used in the near future to model more complex layouts. The experimental study shows that the second turbine is deeply affected by the presence of an upstream device and that a compromise between individual device performance and inter-device spacing is necessary. Numerical results show good agreement with the experiment and are promising for the future modelling of turbine farms. © 2013 Elsevier Ltd. All rights reserved.


Mycek P.,CNRS Laboratory of Waves and Complex Media | Mycek P.,French Research Institute for Exploitation of the Sea | Gaurier B.,French Research Institute for Exploitation of the Sea | Germain G.,French Research Institute for Exploitation of the Sea | And 3 more authors.
Renewable Energy | Year: 2014

The ambient turbulence intensity in the upstream flow plays a decisive role in the behaviour of horizontal axis marine current turbines.Experimental trials, run in the IFREMER flume tank in Boulogne-Sur-Mer (France) for two different turbulence intensity rates, namely 3% and 15%, are presented. They show, for the studied turbine configuration, that while the wake of the turbine is deeply influenced by the ambient turbulence conditions, its mean performances turn out to be slightly modified.The presented conclusions are crucial in the view of implanting second generation turbines arrays. In addition, complete and detailed data sets (wake profiles and performance graphs) are made available to the scientific community in order to encourage further comparisons. © 2014 Elsevier Ltd.


Mycek P.,CNRS Laboratory of Waves and Complex Media | Mycek P.,French Research Institute for Exploitation of the Sea | Gaurier B.,French Research Institute for Exploitation of the Sea | Germain G.,French Research Institute for Exploitation of the Sea | And 3 more authors.
Renewable Energy | Year: 2014

The future implantation of second generation marine current turbine arrays depends on the understanding of the negative interaction effects that exist between turbines in close proximity. This is especially the case when the turbines are axially aligned one behind another in the flow. In order to highlight these interaction effects, experiments were performed in a flume tank on 3-bladed 1/30th scale prototypes of horizontal axis turbines.This work focuses on the interactions between two horizontal axis marine current turbines, axially aligned with the upstream flow. Thrust and power coefficients function of the rotation speed of the downstream device are presented. Besides, the wake of each turbine is characterised so as to explain their behaviour.A large range of inter-device distances is considered, as well as two upstream turbulence intensity conditions, namely 3% and 15%. This latter parameter deeply influences the behaviour of a marine current turbine and thus plays a preponderant role in the interactions effects between two devices. Indeed, this study points out that, for the considered turbine and blade geometry, higher ambient turbulence intensity rates (15%) reduce the wake effects, and thus allows a better compromise between inter-device spacing and individual performance. © 2014 Elsevier Ltd.


Cherfils J.M.,CNRS Laboratory of Waves and Complex Media | Pinon G.,CNRS Laboratory of Waves and Complex Media | Rivoalen E.,CNRS Laboratory of Waves and Complex Media | Rivoalen E.,CNRS Optimisation and Reliability in Structural Mechanics lab
Computer Physics Communications | Year: 2012

JOSEPHINE is a parallel Smoothed Particle Hydrodynamics program, designed to solve unsteady free-surface flows. The adopted numerical scheme is efficient and has been validated on a first case, where a liquid drop is stretched over the time. Boundary conditions can also be modelled, as it is demonstrated in a second case: the collapse of a water column. Results show good agreement with both reference numerical solutions and experiments. The use of parallelism allows significant reduction of the computational time, even more with large number of particles. JOSEPHINE has been written so that any untrained developers can handle it easily and implement new features. © 2012 Elsevier B.V. All rights reserved.


Poupardin A.,CNRS Laboratory of Waves and Complex Media | Perret G.,CNRS Laboratory of Waves and Complex Media | Pinon G.,CNRS Laboratory of Waves and Complex Media | Bourneton N.,CETE | And 2 more authors.
European Journal of Mechanics, B/Fluids | Year: 2012

This paper presents the vortex dynamics generated by the interaction of a submerged horizontal plate, considered as a vortex generator, and a monochromatic wave. The velocity and vorticity fields are determined experimentally using PIV technique for different resolutions in order to study the global flow around the plate and the formation and advection of vortices upstream and downstream of the plate. The global flow around the plate shows great discrepancies with the potential flow solution: two recirculation cells are formed beneath the plate, the global flow is non-symmetric and the advection of vortices induces strong velocities not represented by the potential flow theory. The formation of vortices at the edges of the plate is characterised. At each period, one vortex is formed at the edge followed by the formation of an opposite sign vortex. The upstream and downstream vortex pairs are then advected in front of the plate and toward the bottom respectively, over a distance of about one third the plate length. The lifetime of vortices is about two wave periods. This study will help us validate a numerical software to be used for analysing the influence of various parameters on the dynamics. These results will be presented in the second part of this paper. © 2012 Elsevier Masson SAS. All rights reserved.


Huang C.,CNRS Optimisation and Reliability in Structural Mechanics lab | El Hami A.,CNRS Optimisation and Reliability in Structural Mechanics lab | Radi B.,French National Institute for Agricultural Research
Engineering Optimization | Year: 2016

This article proposed a metamodel-based inverse method for material parameter identification and applies it to elastic–plastic damage model parameter identification. An elastic–plastic damage model is presented and implemented in numerical simulation. The metamodel-based inverse method is proposed in order to overcome the disadvantage in computational cost of the inverse method. In the metamodel-based inverse method, a Kriging metamodel is constructed based on the experimental design in order to model the relationship between material parameters and the objective function values in the inverse problem, and then the optimization procedure is executed by the use of a metamodel. The applications of the presented material model and proposed parameter identification method in the standard A 2017-T4 tensile test prove that the presented elastic–plastic damage model is adequate to describe the material's mechanical behaviour and that the proposed metamodel-based inverse method not only enhances the efficiency of parameter identification but also gives reliable results. © 2016 Informa UK Limited, trading as Taylor & Francis Group


Pinon G.,CNRS Laboratory of Waves and Complex Media | Mycek P.,CNRS Laboratory of Waves and Complex Media | Mycek P.,French Research Institute for Exploitation of the Sea | Germain G.,French Research Institute for Exploitation of the Sea | And 2 more authors.
Renewable Energy | Year: 2012

This paper presents numerical computations of three bladed horizontal axis marine current turbines in a uniform free upstream current. The unsteady evolution of the turbine wake is taken into account by some three-dimensional software, developed to assess the disturbances generated in the sea. An unsteady Lagrangian method is considered for these computations using " Vortex Method" ; a velocity-vorticity numerical implementation of the Navier-Stokes equations. The vortex flow is discretised with particles carrying vorticity, which are advected in a Lagrangian frame. The present paper aims at presenting results on both power and thrust coefficient (C P and C T) predictions and wake characterisation, up to ten diameters downstream of the turbine. Moreover, two different marine current turbines configurations are considered: one is taken from literature [1] and the second one is an open-modified version of turbine inspired from previous works [2]. © 2012 Elsevier Ltd.


Zidani H.,CNRS Optimisation and Reliability in Structural Mechanics lab | Zidani H.,Sina | Pagnacco E.,CNRS Optimisation and Reliability in Structural Mechanics lab | Sampaio R.,Pontifical Catholic University of Rio de Janeiro | And 2 more authors.
Engineering Optimization | Year: 2013

In this article two linear problems with random Gaussian loading are transformed into multi-objective optimization problems. The first problem is the design of a pillar geometry with respect to a compressive random load process. The second problem is the design of a truss structure with respect to a vertical random load process for several frequency bands. A new algorithm, motivated by the Pincus representation formula hybridized with the Nelder-Mead algorithm, is proposed to solve the two multi-objective optimization problems. To generate the Pareto curve, the normal boundary intersection method is used to produce a series of constrained single-objective optimizations. The second problem, depending on the frequency band of excitation, can have as Pareto curve a single point, a standard Pareto curve, or a discontinuous Pareto curve, a fact that has been reported here for the first time in the literature, to the best of the authors knowledge. © 2013 Taylor & Francis Group, LLC.

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