Publications

2013

• Climatologie des états de mer en Atlantique nord-est : analyse du climat actuelet des évolutions futures sous scénarios de changement climatique par descente d'échelle dynamique et statistique
  
  • Laugel Amélie
  , 2013. L'analyse de la climatologie des aléas océano-météorologiques tels que les états de mer est fondamentale pour comprendre l'évolution et la dynamique des zones côtières, estimer les risques naturels survenant lors d'événements de tempête majeurs, définir les moyens optimaux de protection des ports et infrastructures onshore et offshore, caractériser la ressource houlomotrice pour des projets de récupération d'énergie des vagues, comprendre les processus d'érosion et accrétion des plages, etc. Pour répondre à ces problématiques dans un contexte de questionnement croissant sur les conséquences potentielles associées au changement climatique, le travail de thèse s'inscrit dans une démarche double : (i) approfondissement de la connaissance du climat de vagues actuel le long des côtes Atlantique, Manche et Mer du Nord en France d'une part, et (ii) estimation des évolutions futures potentielles de cette climatologie des vagues pour différents scénarios d'évolution climatique. L'estimation de l'impact du changement climatique sur le climat de vague se compose de trois éléments principaux : (i) une connaissance détaillée de la variabilité climatique actuelle des états de mer, (ii) l'utilisation de scénarios de changement climatique à l'horizon 2100 et (iii) la définition d'une méthodologie de descente d'échelle adaptée. Pour appréhender ces sujets, l'Atlas Numérique d'Etats de Mer Océanique et Côtier ANEMOC-2 a été construit à l'aide du modèle spectral de 3ème génération TOMAWAC (Benoit et al., 1996) sur la période 1979-2009 et le climat de vagues futur a été simulé à l'horizon 2100 par des méthodes de descente d'échelle dynamique et statistique en considérant les scénarios de changement climatique du quatrième rapport du GIEC (IPCC, 2007).En particulier, un travail original de comparaison de projections d'états de mer par approche dynamique et par approche statistique des types de temps a été réalisé sur la période 2061-2100 pour les scénarios B1, A1B et A2 simulés par le modèle ARPEGE-CLIMAT de Météo-France (Salas-Mélia, et al. 2005). Les résultats des deux approches (à savoir hauteur significative, période moyenne, direction moyenne et flux d'énergie des vagues) ont été comparés en termes de valeurs moyennes, écarts-types, distributions jointes et variabilités saisonnière et interannuelle. Ce travail a abouti à une estimation de l'impact du changement climatique sur la climatologie des états de mer le long des côtes Atlantique, Manche et Mer du Nord françaises sur la période 2061-2100 en tenant compte des incertitudes intrinsèques aux méthodes de descente d'échelle et aux scénarios de changement climatique. En hiver par exemple, nous observons une augmentation des valeurs moyennes et de la variabilité des paramètres de hauteur significative, période moyenne et flux d'énergie des vagues, notamment en Mer du Nord (pour les scénarios B1, A1B et A2) et dans le Golfe de Gascogne pour le scénario B1. En complément, ces paramètres d'états de mer ont tendance à diminuer dans le Golfe de Gascogne pour les saisons printemps, été et automne. Enfin, les paramètres d'états de mer associés aux hauteurs de vagues du quantile 95 tendent à augmenter sur une large emprise de l'Atlantique nord-est (10.70675/8c696ce0zf650z4f80zaffazdfee30454086)
  DOI : 10.70675/8c696ce0zf650z4f80zaffazdfee30454086
• On the modelling of WECs in wave models using far field coefficients
  
  • Babarit Aurélien
  • Matt Folley
  • Charrayre François
  • Peyrard Christophe
  • Benoit Michel
  , 2013. Time domain (phase resolved) and spectral (phase averaged) wave models are the usual numerical tools for studying wave climate evolution, coastal processes and environmental impacts at regional scale. However, it is not straightforward to model a WEC or a WEC array in such models. At present there have been attempts in which the WECs are modelled as sinks and sources coefficients, these coefficients having been calibrated empirically. This method only partially addresses the underlying physics. In contrast, this paper presents a method which is seen as superior because it addresses better the problem, particularly in case of oscillating WECs or OWCs. The method couples the BEM approach and phase resolved or phase averaged approaches. It makes use of far field coefficients from BEM (also know as the Kochin function) which can be integrated in wave propagation models. First, the theory for the calculation of the far field coefficients is recalled as well as the underlying assumptions. Then, a methodology for coupling with phase resolved wave models is proposed. It makes use of domain decomposition. Comparison of results obtained with the proposed coupled method with direct approach shows excellent agreement, which confirms the potential of the method. Eventually, a methodology for coupling with spectral wave models is envisaged.
• Physical modelling of an array of 25 heaving wave energy converters to quantify variation of response and wave conditions
  
  • Troch Peter
  • Stratigaki Vasiliki
  • Stallard Tim
  • Forehand David
  • Folley Matt
  • Kofoed Jens-Peter
  • Benoit Michel
  • Babarit Aurélien
  • Gallach-Sánchez David
  • de Bosscher Lieselot
  • Rauwoens Pieter
  • Elsässer Björn
  • Lamont-Kane Paul
  • Mccallum Peter
  • Mcnatt Cameron
  • Angelelli Elisa
  • Percher Arthur
  • Carpintero Moreno Efrain
  • Bellew Sarah
  • Dombre Emmanuel
  • Charrayre François
  • Vantorre Marc
  • Kirkegaard Jens
  • Carstensen Stefaan
  , 2013. Experiments have been performed in the Shallow Water Wave Basin of DHI, in Denmark, on large arrays of up to 25 heaving point absorbers for a range of layout configurations and wave conditions. Float response and modification of the wave field are measured to provide data suitable for the evaluation of array interaction models and environmental scale models. Each wave energy converter unit has a diameter of 0.315 m and power absorption is due to friction of both a power take off system and bearings. Response is measured on all floats and surge force on five floats. Wave gauges are located within and around the array. Wave conditions studied include regular waves and both long- and short-crested irregular waves. A rectilinear arrangement of support structures is employed such that several float configurations can be studied. A summary is presented of the experimental arrangement with particular emphasis on the individual wave energy converters and wave conditions employed. Reasonable agreement is observed between measured response for single floats and power output and float response predicted using a linear time domain model. For an array of 25 floats, up to 16.3% reduction of significant wave height is observed down-wave and 10.8% increase observed up-wave for unidirectional irregular waves due to wave radiation by the heaving WECs. Spectra at different locations within and around the array show the wave field modifications.
• Large-scale morphodynamic modelling of the Gironde estuary, France
  
  • Huybrechts Nicolas
  • Villaret Catherine
  Proceedings of the ICE - Maritime Engineering, Thomas Telford, 2013, 166 (2), pp.51-62. Previous attempts at morphodynamic modelling in complex estuarine configuration employ simplifying methods in order to reduce computational cost. Thanks to tremendous progress in numerical and parallelism methods, the open source finite-element Telemac system is applied to represent the medium term bed evolution in the largest estuary in France, the Gironde macro-tidal estuary. A depth-averaged approach is selected here as a good compromise between model accuracy and computational cost. Computations are performed using as bed material either uniform sand or graded sand. Both approaches are compared on measurements of suspended load and bed changes. The suspended rates are better reproduced by the graded sediment assumption and the morphodynamic model results show qualitative agreement with observations of the bed evolution in the central part of the estuary. (10.1680/maen.2012.18)
  DOI : 10.1680/maen.2012.18
• An AHP-derived method for mapping the physical vulnerability of coastal areas at regional scales
  
  • Le Cozannet Gonéri
  • Garcin Manuel
  • Bulteau Thomas
  • Mirgon Carola
  • Yates Marissa L.
  • Méndez Marta
  • Baills Audrey
  • Idier Déborah
  • Oliveros Carlos
  Natural Hazards and Earth System Sciences, Copernicus Publ. / European Geosciences Union, 2013, 13, pp.1209-1227. Assessing coastal vulnerability to climate change at regional scales is now mandatory in France since the adoption of recent laws to support adaptation to climate change. However, there is presently no commonly recognised method to assess accurately how sea level rise will modify coastal processes in the coming decades. Therefore, many assessments of the physical component of coastal vulnerability are presently based on a combined use of data (e.g. digital elevation models, historical shoreline and coastal geomorphology datasets), simple models and expert opinion. In this study, we assess the applicability and usefulness of a multi-criteria decision-mapping method (the analytical hierarchy process, AHP) to map physical coastal vulnerability to erosion and flooding in a structured way. We apply the method in two regions of France: the coastal zones of Languedoc-Roussillon (north-western Mediterranean, France) and the island of La Réunion (south-western Indian Ocean), notably using the regional geological maps. As expected, the results show not only the greater vulnerability of sand spits, estuaries and low-lying areas near to coastal lagoons in both regions, but also that of a thin strip of erodible cliffs exposed to waves in La Réunion. Despite gaps in knowledge and data, the method is found to provide a flexible and transportable framework to represent and aggregate existing knowledge and to support long-term coastal zone planning through the integration of such studies into existing adaptation schemes. (10.5194/nhess-13-1209-2013)
  DOI : 10.5194/nhess-13-1209-2013
• Modelling sedimentation-consolidation in the framework of a one-dimensional two-phase flow model
  
  • Chauchat Julien
  • Guillou Sylvain
  • Pham van Bang Damien
  • Nguyen Kim Dan
  Journal of Hydraulic Research, Taylor & Francis, 2013, 51 (3), pp.293-305. A one-dimensional vertical two-phase flow model for sedimentation-consolidation process is presented. The model is based on solving the continuity and momentum equations for both fluid and solid phases. In the non-cohesive case, the momentum transfer between the two phases is reduced to the drag force around a single particle modified to take the hindrance effects into account. In the cohesive case, Darcy-Gersevanov's law is used for the closure of the momentum transfer between the two phases and the concept of "effective stress" is introduced to take into account the bed structuring. These closure laws are validated against high resolution experimental data in terms of settling curves and concentration profiles. The reliability of the model is illustrated from an analysis of the momentum balances at different stages during the process. Finally, the proposed closure laws and numerical algorithms are shown to be able to quantitatively reproduce sedimentation of non-cohesive and sedimentation- consolidation of cohesive sediments, including mud. (10.1080/00221686.2013.768798)
  DOI : 10.1080/00221686.2013.768798
• Multidecadal Atoll Shoreline Change on Manihi and Manuae, French Polynesia
  
  • Yates Marissa L.
  • Le Cozannet Gonéri
  • Garcin Manuel
  • Salai Emilie
  • Walker Patrice
  Journal of Coastal Research, Coastal Education and Research Foundation, 2013, 29 (4), pp.870-882. As interest in the impact of sea-level rise on atoll islands increases, this study contributes to the growing database of observations of shoreline changes on South Pacific Islands, where few observations are currently available. Historical aerial photographs and recent satellite images were used to evaluate multidecadal surface area and shoreline changes on two atolls in French Polynesia: Manihi and Manuae. During the 40- to 50-year study period, atoll island surface area primarily increased or remained stable on Manihi and decreased on Manuae. Distinct ocean and lagoon shoreline changes were observed in different geographical regions of each atoll. On Manihi, ocean shoreline accretion rates were larger on the NW rim than the SE rim. On Manuae, atoll islands on the NE rim were eroding on the lagoon side and accreting on the ocean side, whereas islands on the SE rim showed the opposite trend. Sea-level rise is often thought to cause atoll erosion, but in this study, lagoon and ocean shorelines both eroded and accreted over a period when sea-level rise rates were greater than the global mean. Surface area changes related directly to anthropogenic activities were identified on only two of the 47 atoll islands. After completing a classification of the incident wave field, it was hypothesized that waves have an important role in controlling the shoreline change variability. Additional field surveys and in situ observations are needed to validate this hypothesis and to understand better island response to changing forcing factors. (10.2112/JCOASTRES-D-12-00129.1)
  DOI : 10.2112/JCOASTRES-D-12-00129.1
• Unified semi-analytical wall boundary conditions for inviscid, laminar or turbulent flows in the meshless SPH method
  
  • Ferrand Martin
  • Laurence Dominique R.
  • Rogers Benedict D.
  • Violeau Damien
  • Kassiotis Christophe
  International Journal for Numerical Methods in Fluids, Wiley, 2013, 71 (476-472), pp.Online. Wall boundary conditions in smoothed particle hydrodynamics (SPH) is a key issue to perform accurate simulations. We propose here a new approach based on a renormalising factor for writing all boundary terms. This factor depends on the local shape of a wall and on the position of a particle relative to the wall, which is described by segments (in two-dimensions), instead of the cumbersome fictitious or ghost particles used in most existing SPH models. By solving a dynamic equation for the renormalising factor, we significantly improve traditional wall treatment in SPH, for pressure forces, wall friction and turbulent conditions. The new model is demonstrated for cases including hydrostatic conditions for still water in a tank of complex geometry and a dam break over triangular bed profile with sharp angle where significant improved behaviour is obtained in comparison with the conventional boundary techniques. The latter case is also compared with a finite volume and volume-of-fluid scheme. The performance of the model for a two-dimensional laminar flow in a channel is demonstrated where the profiles of velocity are in agreement with the theoretical ones, demonstrating that the derived wall shear stress balances the pressure gradient. Finally, the performance of the model is demonstrated for flow in a schematic fish pass where both the velocity field and turbulent viscosity fields are satisfactorily reproduced compared with mesh-based codes. (10.1002/fld.3666)
  DOI : 10.1002/fld.3666
• A new model for shallow viscoelastic fluids
  
  • Bouchut François
  • Boyaval Sébastien
  Mathematical Models and Methods in Applied Sciences, World Scientific Publishing, 2013, 23 (8), pp.1479-1526. We propose a new reduced model for gravity-driven free-surface flows of shallow elastic fluids. It is obtained by an asymptotic expansion of the upper-convected Maxwell model for elastic fluids. The viscosity is assumed small (of order epsilon, the aspect ratio of the thin layer of fluid), but the relaxation time is kept finite. Additionally to the classical layer depth and velocity in shallow models, our system describes also the evolution of two scalar stresses. It has an intrinsic energy equation. The mathematical properties of the model are established, an important feature being the non-convexity of the physically relevant energy with respect to conservative variables, but the convexity with respect to the physically relevant pseudo-conservative variables. Numerical illustrations are given, based on a suitable well-balanced finite-volume discretization involving an approximate Riemann solver. (10.1142/S0218202513500140)
  DOI : 10.1142/S0218202513500140
• Physical model experiments for sediment supply to the old Rhine through induced bank erosion
  
  • Die Moran A.
  • El Kadi Abderrezzak K.
  • Mosselman E.
  • Habersack H.
  • Lebert F.
  • Aelbrecht D.
  • Laperrousaz E.
  International Journal of Sediment Research, 2013, 28 (4), pp.431-447. A mobile-bed, undistorted physical model (1: 40) has been used to investigate different sediment supply strategies to the Old Rhine through bank protection removal and modifications of groyne dimensions and configuration, which cause bank erosion. This trained channel was previously the main bed of the upper Rhine downstream of Basel (Switzerland), but it has an artificially low flow regime since the construction of the Grand Canal d'Alsace, a navigation canal, and a flow control dam at Kembs (France). Training works and subsequent channel incision have also greatly reduced sediment transport rates and created a heavily armoured bed. The modelled pilot site has a groyne field on the left bank. Results show that the currently existing groynes at the site are not effective in creating high bank-side velocities conducive to bank erosion, even for flow rates significantly higher than the mean annual flow rate. The river bank has also proved to be more resistant than previously thought, allowing long stretches of bank protection to be safely removed. The physical model testing process has produced a new configuration for the groyne field, where two higher, larger island groynes are placed further apart than the three existing attached groynes. This innovative approach has proved effective, causing bank erosion for flow rates below the mean annual flow rate, with consistent erosion being observed. It has also been found that such a configuration does not pose a hazard for the Grand Canal d'Alsace, which is situated next to the Old Rhine, through excessive bank erosion during high flow events.
• Hindered settling of sand-mud flocs mixtures: From model formulation to numerical validation
  
  • Van L. A.
  • Pham van Bang Damien
  Advances in Water Resources, Elsevier, 2013, 53, pp.1-11. Mixtures of non-cohesive and cohesive sediment are frequently encountered in natural environments such as estuaries. Depending on the concentration of both species, mixed sediment can record segregation effect or not, behaves like a non-cohesive sediment or like a cohesive sediment. The present study deals with the segregation effect between mud flocs and sand grains during hindered settling. Simulations of this process under various conditions of mixture are proposed by using two coupled mass conservation equations which are solved by a high order numerical model. Specific closure equations are proposed herein for the hindered settling of sand-mud mixed sediment. Comparisons between simulations and experiments are presented on vertical concentration profiles during the segregation process. Obviously, the model enables the description of hindered settling for pure non-cohesive (or pure cohesive) case and the segregation for bi-disperse suspensions. © 2012 Elsevier Ltd. (10.1016/j.advwatres.2012.09.009)
  DOI : 10.1016/j.advwatres.2012.09.009
• A Weighted Average Flux (WAF) scheme applied to shallow water equations for real-life applications
  
  • Ata Riadh
  • Pavan Sara
  • Khelladi S.
  • Toro E. F.
  Advances in Water Resources, Elsevier, 2013, 62, pp.155-172. This work focuses on the application of a Weighted Average Flux (WAF) approximation to the shallow water equations with friction and real bathymetry on unstructured two dimensional grids. The scheme obtained must satisfy severe numerical criteria so it can be implemented in the TELEMAC code, widely used in industry.Despite its interesting numerical properties (at least in theory, which includes second order in time and space), WAF approximation is rarely applied to unstructured meshes. Here, we provide a general method for applying the WAF scheme to a homogenous equation. The general and efficient discretization of the topographic source term (through hydrostatic reconstruction) and friction (with a semi-implicit way) is also presented. We applied the approximation using the HLLC Riemann solver within a vertex-centered finite volume framework. The discretization obtained is validated with several theoretical and real benchmarks. The WAF-HLLC scheme proposed is also compared to several other well-known schemes such as HLLC, Roe and Kinetic type schemes. The results obtained show that the behavior of the scheme is encouraging as they demonstrate well-balanceness, strict mass conservation, positivity of water depth, efficient treatment of wetting and drying phenomena, good shock-capturing and low numerical diffusion. Nevertheless, the second order of accuracy in space is not attained with sufficient rigor and remains an open problem requiring more detailed study. © 2013 Elsevier Ltd. (10.1016/j.advwatres.2013.09.019)
  DOI : 10.1016/j.advwatres.2013.09.019
• Large-scale morphodynamic modeling of the Gironde estuary, France
  
  • Huybrechts N.
  • Villaret C.
  Proceedings of the Institution of Civil Engineers: Maritime Engineering, 2013, 166 (2), pp.51-62. Previous attempts at morphodynamic modelling in complex estuarine configuration employ simplifying methods in order to reduce computational cost. Thanks to tremendous progress in numerical and parallelism methods, the open source finite-element Telemac system is applied to represent the medium term bed evolution in the largest estuary in France, the Gironde macro-tidal estuary. A depth-averaged approach is selected here as a good compromise between model accuracy and computational cost. Computations are performed using as bed material either uniform sand or graded sand. Both approaches are compared on measurements of suspended load and bed changes. The suspended rates are better reproduced by the graded sediment assumption and the morphodynamic model results show qualitative agreement with observations of the bed evolution in the central part of the estuary. (10.1680/maen.2012.18)
  DOI : 10.1680/maen.2012.18
• A projection method-based model with the exact C-property for shallow-water flows over dry and irregular bottom using unstructured finite-volume technique
  
  • Shi Y. E.
  • Ray R. K.
  • Nguyen K. D.
  Computers and Fluids, Elsevier, 2013, 76, pp.178-195. A numerical model is presented for simulating shallow-water flows over dry and irregular bottom. The model is based on a projection method, which consists of combining the momentum and continuity equations in order to establish a Poisson-type equation for the water surface level. The computed domain is discretised by finite volumes on an unstructured grid. A 2nd-order upwind scheme coupled with a Least Square technique is used for handling advection terms. The present model ensures the exact C-property that has been theoretically and numerically demonstrated in this paper. Wetting and drying treatment technique used in the model has been also validated by several benchmark tests. The accuracy, stability and reliability of the present model are verified by comparing numerical results with observed data for the Malpasset dam-break event. © 2013 Elsevier Ltd. (10.1016/j.compfluid.2013.02.002)
  DOI : 10.1016/j.compfluid.2013.02.002
• Investigation of wall bounded flows using SPH and the unified semi-analytical wall boundary conditions
  
  • Mayrhofer A.
  • Rogers B. D.
  • Violeau D.
  • Ferrand M.
  Computer Physics Communications, Elsevier, 2013, 184 (11), pp.2515-2527. Semi-analytical wall boundary conditions present a mathematically rigorous framework to prescribe the influence of solid walls in smoothed particle hydrodynamics (SPH) for fluid flows. In this paper they are investigated with respect to the skew-adjoint property which implies exact energy conservation. It will be shown that this property holds only in the limit of the continuous SPH approximation, whereas in the discrete SPH formulation it is only approximately true, leading to numerical noise. This noise, interpreted as a form of "turbulence", is treated using an additional volume diffusion term in the continuity equation which we show is equivalent to an approximate Riemann solver. Subsequently two extensions to the boundary conditions are presented. The first dealing with a variable driving force when imposing a volume flux in a periodic flow and the second showing a generalization of the wall boundary condition to Robin type and arbitrary-order interpolation. Two modifications for free-surface flows are presented for the volume diffusion term as well as the wall boundary condition. In order to validate the theoretical constructs numerical experiments are performed showing that the present volume flux term yields results with an error 5 orders of magnitude smaller then previous methods while the Robin boundary conditions are imposed correctly with an error depending on the order of the approximation. Furthermore, the proposed modifications for free-surface flows improve the behavior at the intersection of free surface and wall as well as prevent free-surface detachment when using the volume diffusion term. Finally, this paper is concluded by a simulation of a dam break over a wedge demonstrating the improvements proposed in this paper. © 2013 Elsevier B.V. All rights reserved. (10.1016/j.cpc.2013.07.004)
  DOI : 10.1016/j.cpc.2013.07.004
• Comparison of local indices for regional frequency analysis with an application to extreme skew surges
  
  • Weiss J.
  • Bernardara P.
  Water Resources Research, American Geophysical Union, 2013, 49 (5), pp.2940-2951. Regional frequency analysis (RFA) is a valuable and well-known method which allows using all the information at the regional scale to improve the actual estimation of the probability of occurrence of extreme events at a given site. In the framework of the index flood method, a local index, representing the local specificities of a given site, is used to normalize at-site observations for the estimation of the regional distribution. It is an essential feature of this model, contrasting with common characteristics shared between the sites of the homogenous region. However, the specification of the local index can be a crucial point. In particular, the performance of the quantile estimator derived from a RFA can depend on the specification of the local index. Four regionalization models are proposed, where the local index is specified by different statistics in each model, and their performances are assessed through Monte Carlo simulations of several regional scenarios. Some guidelines are provided for the selection of the local index which is most adapted to the observed situation (including regional scenarios characterized by some degrees of asymmetry, homogeneity and inter-site correlation). A practical application on extreme skew storm surges is provided to illustrate the results. ©2013. American Geophysical Union. All Rights Reserved. (10.1002/wrcr.20225)
  DOI : 10.1002/wrcr.20225
• A posteriori analysis of Chorin-Temam scheme for Stokes equations
  
  • Boyaval Sébastien
  • Picasso M.
  Comptes Rendus. Mathématique, Académie des sciences (Paris), 2013, 351 (23-24), pp.931-936. We consider Chorin-Temam scheme (the simplest pressure-correction projection method) for the time-discretization of an unstationary Stokes problem. Inspired by the analyses of the Backward Euler scheme performed by C.Bernardi and R.Verfürth, we derive a posteriori estimators for the error on the velocity gradient in L2 norm. Our invesigation is supported by numerical experiments. (10.1016/j.crma.2013.10.026)
  DOI : 10.1016/j.crma.2013.10.026
• Validation expérimentale d'un modèle double-couche pour des vagues côtières non-linéaires et fortement dispersives
  
  • Benoit Michel
  • Chazel Florent
  Revue Paralia, Editions Paralia CFL, 2013, 6, pp.7.1-7.16. Le modèle original proposé par les auteurs (CHAZEL et al., 2009) pour les vagues en zone côtière est mis en œuvre et validé sur deux cas expérimentaux. Nous considérons d'abord les expériences de DINGEMANS (1994), étudiant la propagation de vagues régulières au-dessus d'une barre trapézoïdale immergée. Les résultats numériques démontrent une excellente capacité du modèle à reproduire les effets de levée, les interactions fortement non-linéaires, ainsi que la génération puis la propagation de composantes harmoniques d'ordres élevés après la barre. Ensuite, nous vérifions la capacité du modèle à propager des vagues irrégulières non-déferlantes sur une bathymétrie plus complexe (essai 26 de BECQ-GIRARD et al., 1999). L'analyse et la comparaison des spectres de variance montrent que les résultats du modèle sont également en très bon accord avec les mesures expérimentales. (10.5150/revue-paralia.2013.007)
  DOI : 10.5150/revue-paralia.2013.007
• Numerical modelling of wave current interactions at a local scale
  
  • Teles M. J.
  • Pires-Silva A. A.
  • Benoit M.
  Ocean Modelling, Elsevier, 2013, 68, pp.72-87. The present work is focused on the evaluation of wave-current interactions through numerical simulations of combined wave and current flows with the Code_Saturne (Archambeau et al., 2004), an advanced CFD solver based on the RANS (Reynolds Averaged Navier-Stokes) equations. The objectives of this paper are twofold. Firstly, changes in the mean horizontal velocity and the horizontal-velocity amplitude profiles are studied when waves are superposed on currents. The influence of various first and second order turbulence closure models is addressed. The results of the numerical simulations are compared to the experimental data of Klopman (1994) and Umeyama (2005). Secondly, a more detailed study of the shear stresses and the turbulence viscosity vertical profile changes is also pursued when waves and currents interact. This analysis is completed using the data from Umeyama (2005). A relationship between a non-dimensional parameter involving the turbulence viscosity and the Ursell number is subsequently proposed. © 2013 Elsevier Ltd. (10.1016/j.ocemod.2013.04.006)
  DOI : 10.1016/j.ocemod.2013.04.006
• Experimental evidence of the modulation of a plane wave to oblique perturbations and generation of rogue waves in finite water depth
  
  • Toffoli A.
  • Fernandez L.
  • Monbaliu J.
  • Benoit M.
  • Gagnaire-Renou E.
  • Lefevre J. M.
  • Cavaleri L.
  • Proment D.
  • Pakozdi C.
  • Stansberg C. T.
  • Waseda T.
  • Onorato M.
  Physics of Fluids, American Institute of Physics, 2013, 25 (9). We present a laboratory experiment in a large directional wave basin to discuss the instability of a plane wave to oblique side band perturbations in finite water depth. Experimental observations, with the support of numerical simulations, confirm that a carrier wave becomes modulationally unstable even for relative water depths k(0)h < 1.36 (with k the wavenumber of the plane wave and h the water depth), when it is perturbed by appropriate oblique disturbances. Results corroborate that the underlying mechanism is still a plausible explanation for the generation of rogue waves in finite water depth. (C) 2013 AIP Publishing LLC. (10.1063/1.4821810)
  DOI : 10.1063/1.4821810
• Morphodynamic modeling using the Telemac finite-element system
  
  • Villaret C.
  • Hervouet J. M.
  • Kopmann R.
  • Merkel U.
  • Davies A. G.
  Computers & Geosciences, Elsevier, 2013, 53, pp.105-113. The open-source finite-element system Telemac has been applied to simulate various complex hydrodynamic and morphodynamic situations including waterways, curved channels, recirculating flows and wave-induced littoral transport. In the applications presented here, the sediment transport model is mainly restricted to the transport of non-cohesive sediments, which relies on classical semi-empirical concepts including sand grading effects, parameterization of secondary currents and wave effects. In comparison with other comprehensive modeling systems (Delft-3D, Mike-21, etc.), the main originality lies in the efficiency and flexibility of the finite elements. Thanks to the optimization of numerical schemes, parallelism, as well as tremendous progress in the performance of computers, bed evolution can be calculated on basin scale (10-100. km) and for the medium term (years to decades), without the use of hydrodynamic filtering methods. As a novelty in release 6.0, we present a method of feedback for the bed roughness, which reduces uncertainty in the prediction of both transport rates and flow velocities. © 2011 Elsevier Ltd. (10.1016/j.cageo.2011.10.004)
  DOI : 10.1016/j.cageo.2011.10.004