Publications

2012

• Numerical modelling of sand-mud mixtures settling and transport processes : application to morphodynamic of the Gironde estuary (France)
  
  • Van Lan Anh
  , 2012. This study attempts to model sediment transport rates and the resulting bed evolution in a complex estuarine environment: the Gironde estuary, characterized by a high hetereogeneity in the sediment bed composition, with the presence of both cohesive and non-cohesive sediments and sand/mud mixtures. Our main objective is to extend an existing 2D morphodynamic model developped by Huybrechts et al (2012b) for non-cohesive sediments, to account for the presence of mud and to draw some preliminary step for a fully mixte sediment morphodynamic model. Our framework is the finite element Telemac system (release 6.1), where the two-dimensional (depth averaged) approach has been selected for large scale and medium term simulations.The first part of this work is devoted to the understanding of sedimentation-consolidation processes for pure mud, combining laboratory experiments and 1D vertical models. Cohesive processes are then integrated in the 2D (depth-averaged) large scale morphodynamic model of the Gironde estuary developed by Huybrechts et al. (2012b). Erosion/deposition experiments were performed at the RWTH laboratory (University of Aachen, Germany) to calibrate the erosion and deposition law parameters. Moreover, the effect of consolidation is taken into account through the implementation of a 1DV Gibson-based sedimentation-consolidation model (Thiebot et al., 2011) using analytical closure equations for permeability and effective stress. Special attention is paid to the initialisation of the bed structure. Comparisons between measurements and model results are achieved on both suspended sediment concentration records and on medium term (5-year) bed evolutions.In the second part, a new 1DV model for the hindered settling of sand-mud mixtures has been developed based on the background of non-cohesive bi-disperse models. The numerical solution has been constructed by considering a high-order of accuracy in space via a Weighted Essentially Non Oscillatory (WENO) reconstruction technique and in time via a local space-time Discontinuous Galerkin (DG).The model is then validated against a large range of experimental data (mono-disperse sand, mud, non-cohesive bi-disperse and non-cohesive/cohesive mixture) (10.70675/20b9e715z81c2z4c80zb4baz758beaaba171)
  DOI : 10.70675/20b9e715z81c2z4c80zb4baz758beaaba171
• Numerical wave modeling in conditions with strong currents: dissipation, refraction, and relative wind. Journal of Physical Oceanography
  
  • Ardhuin Fabrice
  • Roland Aron
  • Dumas Franck
  • Bennis Anne-Claire
  • Sentchev Alexei
  • Forget Philippe
  • Wolf Judith
  • Girard Françoise
  • Osuna Pedro
  • Benoit Michel
  Journal of Physical Oceanography, American Meteorological Society, 2012, 42 (12), pp.2101-2120. Currents effects on waves have led to many developments in numerical wave modeling over the past two decades, from numerical choices to parameterizations. The performance of numerical models in conditions with strong currents is reviewed here, and observed strong effects of opposed currents and modulations of wave heights by tidal currents in several typical situations are interpreted. For current variations on small scales, the rapid steepening of the waves enhances wave breaking. Using different parameterizations with a dissipation rate proportional to some measure of the wave steepness to the fourth power, the results are very different, none being fully satisfactory, which points to the need for more measurements and further refinements of parameterizations. For larger-scale current variations, the observed modifications of the sea state are mostly explained by refraction of waves over currents and relative wind effects, that is, the wind speed relevant for wave generation is the speed in the frame of reference moving with the near-surface current. It is shown that introducing currents in wave models can reduce the errors on significant wave heights by more than 30% in some macrotidal environments, such as the coast of Brittany, in France. This large impact of currents is not confined to the locations where the currents are strongest, but also downwave from strong current gradients. (10.1175/JPO-D-11-0220.1)
  DOI : 10.1175/JPO-D-11-0220.1
• Modélisation du transport des nappes d'hydrocarbures en zone continentale et estuarienne
  
  • Goeury Cédric
  , 2012. L'application de la Directive Cadre sur l'Eau et l'obligation de surveillance de la qualité d'eau pour la consommation humaine et les activités récréatives ou industrielles, telles que la production d'eau potable, entraînent une forte demande pour des systèmes d'évaluation et de suivi de la qualité de l'eau. Le projet de recherche MIGR'HYCAR (http://www.migrhycar.com) a donc été mis en place pour répondre à un besoin opérationnel et à un défaut d'outils d'aide à la décision adaptés face aux déversements d'hydrocarbures en eaux continentales (rivières, lacs et estuaires) qui représente plus de 50% des déversements accidentels en France. Au cours du projet de recherche MIGR'HYCAR, un modèle mathématique de dérive de nappe d'hydrocarbures, composé d'un modèle lagrangien couplé à un modèle eulérien, a été développé dans la plate-forme hydro-informatique TELEMAC (http://www.opentelemac.org). Le modèle lagrangien décrit le mouvement de la nappe en surface en considérant celle-ci comme un ensemble de particules. Ainsi le modèle développé est capable de modéliser les principaux phénomènes agissant sur une nappe d'hydrocarbures une fois celle-ci déversée : convection, diffusion, échouage, re-largage, étalement, évaporation, dissolution et volatilisation. Bien que le phénomène de dissolution ne concerne qu'un très faible volume d'hydrocarbures, ce processus peut avoir des conséquences importantes du point de vue de la toxicité. Afin de suivre l'évolution du pétrole dissous, un modèle eulérien de suivi de traceurs a été adopté. La quantité de traceur dépend directement de la masse dissoute des particules lagrangiennes. Cette approche permet le suivi des hydrocarbures dissous dans la colonne d'eau. Des cinétiques effectuées en laboratoire ont pour but la calibration du modèle numérique. En complément de cas tests issus de la littérature et de cas réels, des résultats expérimentaux issus d'expérimentations effectuées en canal d'essai doivent permettre de vérifier et valider la qualité des simulations numériques sur des situations où les conditions ne sont que partiellement contrôlées (10.70675/9ed57b7czb112z45f6z98a1zfb78a0146ab6)
  DOI : 10.70675/9ed57b7czb112z45f6z98a1zfb78a0146ab6
• A one dimensional (1-D) numerical modelling of pesticide transfer through the wetland drainage channels of Breton-Vendéen marsh (west coast of France)
  
  • Gille Julian
  • El Kadi Abderrezzak K.
  • Zaoui F.
  • Robin Marc
  • Gaillard Stephan
  , 2012. Predicting pollutant transport in coastal ecosystems has become an important topic in many industrial and environmental projects, because of the degradation of water quality and conflicts related to multiple use of coastal resources. Most numerical studies on coastal catchment do not consider flow and pollutant fluxes through wetlands, or simulates theses transfers using “black box” based on linear regressions that greatly simplifies the complexity of the underlying processes. This paper presents a numerical study on the simulation of pesticide transport and degradation in the artificial wetland drainage channels of the Breton-Vendéen marsh (west coast of France). The one-dimensional (1-D), open source MASCARET modelling tool is used. The 1-D unsteady water flow through a network of open channels is represented by the shallow water equations. The water quality module of MASCARET simulates solute transport processes, consisting of advection, dispersion and mass reduction/generation by physical, chemical and biological mechanisms. Results show that the 1-D model is a reliable tool for simulating pollutant transfer through the coastal wetlands drainage channels. Moreover, it is possible to link landward and seaward models to MASCARET, which allows simulating water and pollutant propagation from watershed to coastal sea through wetland drainage channels with a high level of confidence
• A fast Monte-Carlo method with a Reduced Basis of Control Variates applied to Uncertainty Propagation and Bayesian Estimation
  
  • Boyaval Sébastien
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2012, 241-244, pp.190-205. The Reduced-Basis Control-Variate Monte-Carlo method was introduced recently in [S.Boyaval and T. Lelievre, CMS, 8 2010] as an improved Monte-Carlo method, for the fast estimation of many parametrized expected values at many parameter values. We provide here a more complete analysis of the method including precise error estimates and convergence results. We also numerically demonstrate that it can be useful to some parametrized frameworks in Uncertainty Quantification, in particular (i) the case where the parametrized expectation is a scalar output of the solution to a Partial Differential Equation (PDE) with stochastic coefficients (an Uncertainty Propagation problem), and (ii) the case where the parametrized expectation is the Bayesian estimator of a scalar output in a similar PDE context. Moreover, in each case, a PDE has to be solved many times for many values of its coefficients. This is costly and we also use a reduced basis of PDE solutions like in [S. Boyaval, C. Le Bris, Nguyen C., Y. Maday and T. Patera, CMAME, 198 2009]. This is the first combination of various Reduced-Basis ideas to our knowledge, here with a view to reducing as much as possible the computational cost of a simple approach to Uncertainty Quantification. (10.1016/j.cma.2012.05.003)
  DOI : 10.1016/j.cma.2012.05.003
• A one-dimensional two-phase flow approach for sedimentation-consolidation modelling
  
  • Chauchat Julien
  • Guillou Sylvain
  • Pham van Bang Damien
  • Nguyen Kim Dan
  , 2012, pp.249-256. A 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. 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 account for the bed structuring. These closure laws are validated against high resolution experimental data in terms of settling curves and concentration profiles. The good agreement obtained between numerical results and experimental data shows the predictive capability of the two-phase model. (10.5150/jngcgc.2012.025-c)
  DOI : 10.5150/jngcgc.2012.025-c
• Future extreme water levels and floodplains in Gironde Estuary considering climate change
  
  • Laborie Vanessya
  • Hissel François
  • Sergent Philippe
  , 2012.
• Efficient coupling algorithm for free-surface flow impacting complex structures
  
  • Kassiotis Christophe
  • Matthies Hermann G.
  • Ibrahimbegovic Adnan
  , 2012, pp.184-185.
• Sea level rise with respect to other causes of coastal erosion: examples in the Pacific
  
  • Le Cozannet Gonéri
  • Cazenave Anny
  • Salas y Melia David
  • Wöppelmann Guy
  • Donato Vincent
  • Walker Patrice
  • Rogel Philippe
  • Garcin Manuel
  • Yates Marissa L.
  , 2012. Sea level changes show significant regional variability due to variations in ocean temperature. In some oceanic regions, sea level has risen quicker than the global average. However, we show from some examples in the Pacific Ocean that even in those case, shoreline changes are often still controlled by other factors such as waves, extreme events or direct and indirect anthropogenic actions. This statement favors adaptation strategies that focus initially on reducing vulnerability to current hazards such as temporary flooding. This study was carried out in the framework of the CECILE project, which is supported by the French Agency for Research (ANR).
• A fully nonlinear implicit model for wave interactions with submerged structures in forced or free motion
  
  • Guerber Etienne
  • Benoit Michel
  • Grilli Stephan T.
  • Buvat Clément
  Engineering Analysis with Boundary Elements, Elsevier, 2012, 36, pp.1151-1163. The purpose of this work is to develop advanced numerical tools for modeling two-way fully nonlinear interactions of ocean surface waves (irregular waves in the general situation) with submerged structures undergoing large amplitude motion, that could represent Wave Energy Converters (WECs). In our modeling approach, an existing two-dimensional Numerical Wave Tank (NWT), based on potential flow theory, is extended to include a submerged horizontal cylinder of arbitrary cross-section. The mathematical problem and related numerical solution are first introduced. Then, conservation of volume and conservation of energy are checked, respectively, in the case of a circular cylinder in a prescribed large amplitude motion and in the case of a circular cylinder in a free motion. Interactions between waves and a submerged circular cylinder computed by the model are then compared to mathematical solutions for two situations: a cylinder in prescribed motion and a freely moving cylinder. (10.1016/j.enganabound.2012.02.005)
  DOI : 10.1016/j.enganabound.2012.02.005
• Tsunami impact on coastal structures: partitioned solution procedure for fluid-structure interaction with free-surface flow
  
  • Ibrahimbegovic Adnan
  • Kassiotis Christophe
  • Matthies Hermann G.
  , 2012, pp.546-555.
• Sediment transport modelling : Relaxation schemes for Saint-Venant -- Exner and three layer models
  
  • Audusse Emmanuel
  • Chalons Christophe
  • Delestre Olivier
  • Goutal Nicole
  • Jodeau Magali
  • Sainte-Marie Jacques
  • Giesselmann Jan
  • Sadaka Georges
  , 2012. In this note we are interested in the modelling of sediment transport phenomena. We mostly focus on bedload transport and we do not consider suspension sediment processes. We first propose a coupled numerical scheme for the classical Saint-Venant -- Exner model. It is based on a relaxation approach and it works with all sediment flux function. We exhibit that this coupled approach is more stable than the splitting approach that is mostly used in industrial softwares. Then we derive an original three layers model in order to overcome the difficulties that are encountered when using the classical Exner approach and we write a related relaxation model.
• Transport of isotropic particles in a partially obstructed channel flow
  
  • Joly Antoine
  • Violeau Damien
  • Moulin Frédéric
  • Astruc Dominique
  • Kassiotis Christophe
  Journal of Hydraulic Research, Taylor & Francis, 2012, 50 (3), pp.324-337. The transport of particles in turbulent flows is a common problem in hydraulic engineering. In this paper, the focus is set on a numerical model used to simulate the transport of small bodies (debris, algae, etc.) along a coastline. In this problem, the particles are larger than the small turbulent eddies, but smaller than the large turbulent eddies, and sufficiently diluted within the flow so that each particle does not affect the flow or the motion of other particles. A mixed Eulerian-Lagrangian approach was chosen in order to model a large flow area with sufficient information for the turbulent diffusion. This model is validated through an experiment on particles released into a partially obstructed channel flow. The measurements are then compared with simulations using two Eulerian industrial codes, Telemac-2D and OpenFoam. Finally, an application to algae bloom transport in a harbour is presented. (10.1080/00221686.2012.686457)
  DOI : 10.1080/00221686.2012.686457
• Modélisation spectrale des états de mer par un calcul quasi-exact des interactions non-linéaires vague-vague
  
  • Gagnaire-Renou Elodie
  • Benoit Michel
  La Houille Blanche - Revue internationale de l'eau, EDP Sciences, 2012, 2012 (3), pp.51-60. (10.1051/lhb/2012023)
  DOI : 10.1051/lhb/2012023
• Diffusion in grid turbulence of isotropic macro-particles using a Lagrangian stochastic method: theory and validation.
  
  • Joly Antoine
  • Moulin Frédéric
  • Violeau Damien
  • Astruc Dominique
  Physics of Fluids, American Institute of Physics, 2012, 24, pp.103303. The prediction of solid bodies transport (such as algae, debris, sediment grains, or corrosion deposits) is a necessary requirement in many industrial or environmental processes. The physical processes involved cover a wide range of processes, from tidal flow to turbulent eddies and particle drag. A stochastic model was therefore developed to link the different scales of the physical processes where it was assumed that the particles are dilute enough that they do not affect the flow or the motion of other particles while being large enough that each particle does not follow exactly the fluid motions (i.e., macro-particles). The stochastic model is built in such a way that it uses Reynolds-averaged fluid properties to predict trajectories of individual particles. This model was then tested using experimental measurements obtained for isotropic particles released in semi-homogeneous turbulence. The turbulent flow was generated using a pair of oscillating grids and was characterized using particle image velocimetry measurements. The trajectories of the particles were measured using a pair of high resolution cameras. The comparison between the experimental data and different numerical models gives satisfactory results. (10.1063/1.4757653)
  DOI : 10.1063/1.4757653
• A family of explicit algebraic models for Reynolds stresses and passive scalar fluxes
  
  • Ferrand Martin
  • Violeau Damien
  Journal of Hydraulic Research, Taylor & Francis, 2012, 50 (5), pp.494-505. (10.1080/00221686.2012.725995)
  DOI : 10.1080/00221686.2012.725995
• Development of a point absorber wave energy converter for investigation of array wake effects in large scale experiments
  
  • Stratigaki Vasiliki
  • Troch Peter
  • Stallard Tim
  • Forehand David
  • Vantorre Marc
  • Kofoed Jens-Peter
  • Babarit Aurélien
  • Benoit Michel
  , 2012. Wave energy from ocean waves is absorbed by using Wave Energy Converters (WECs). In order to extract a considerable amount of wave power at a location, in a cost-effective way, large numbers of WECs have to be arranged in arrays using a particular geo m etric configuration. Interactions between the individual WECs ("near field effects") affect the overall power production of the array. In addition, the wave height reduction behind an entire WEC array ("far field effects") may affect other users in the sea, the environment or even the coastline. Several numerical studies on large WEC arrays have already been performed, but large scale experimental studies, focussing on "near-field" and "far-field" wake effects of large WEC arrays are not available in literature. Within the HYDRALAB IV FP7 European programme, the WECwakes research project has been introduced, in order to perform experiments on large arrays of point absorber WECs, using different geometric configurations and inter-WEC spacings. The selected facility is the Shallow Water Wave Basin of the Danish Hydraulic Institute (DHI), in Denmark. The results from the WECwakes experimental tests will be useful in the validation and extension of the recently developed numerical models, as well as in providing insight to optimizing the geometric configurations of WEC arrays for real applications. The latter, also, aims at cost-effective configurations of WEC arrays for power production, and at quantifying the related environmental impact. The present paper focuses on the preparation of the WECwakes project and the development of the used WEC models.
• Optimized Predictive Two-Dimensional Hydrodynamic Model of the Gironde Estuary in France.
  
  • Huybrechts Nicolas
  • Villaret Catherine
  • Lyard Florent
  Journal of Waterway, Port, Coastal, and Ocean Engineering, American Society of Civil Engineers, 2012, 138 (4), pp.312-322. A two-dimensional hydrodynamic model of the macrotidal Gironde estuary (France) is developed and shown to predict the tide propagation with an accuracy of < 10 cm on water level. The 170-km-long computational domain represents, in detail, the central part of the estuary, characterized by a complex multichannel geometry. This model provides an efficient and accurate operational tool by using an optimized finite-element numerical scheme. Particular attention is paid to the offshore boundary conditions and to the calibration procedure. On the offshore boundary, the tidal signal is decomposed into harmonics whose main amplitudes and phases are obtained from a regional tidal model covering the North East Atlantic. Sensitivity studies are conducted to determine the influence of the harmonics number and harmonic constants on tidal prediction at the mouth. Differences up to 20 ∼ 30 cm in water level at the estuary mouth are observed between the scenarios for the tidal forcing. The calibration of the friction coefficient is thus linked to the tidal forcing scenario. A calibration procedure for the friction coefficient is also presented that can be applied to estuarine conditions. The van Rijn method is applied to predict a first set of values for the friction coefficients as a function of grain size and flow parameters. These predicted mean (time-averaged) coefficients are then adjusted with a maximum of 15% to reproduce in a best way water level and velocity measurements. (10.1061/(ASCE)WW.1943-5460.0000129)
  DOI : 10.1061/(ASCE)WW.1943-5460.0000129
• Simulation of dredged sediment releases into homogeneous water using a two-phase model
  
  • Nguyen Duc Hau
  • Pham van Bang Damien
  • Lévy Florence
  • Guillou Sylvain
  • Nguyen Kim Dan
  • Chauchat Julien
  Advances in Water Resources, Elsevier, 2012, 48, pp.102-112. (10.1016/j.advwatres.2012.03.009)
  DOI : 10.1016/j.advwatres.2012.03.009
• Sediment transport modelling : relaxation schemes for Saint-Venant - Exner and three layer models
  
  • Audusse Emmanuel
  • Chalons Christophe
  • Delestre Olivier
  • Goutal Nicole
  • Jodeau Magali
  • Sainte-Marie Jacques
  • Giesselmann Jan
  • Sadaka Georges
  ESAIM: Proceedings, EDP Sciences, 2012, 38, pp.78-98. In this note we are interested in the modelling of sediment transport phenomena. We mostly focus on bedload transport and we do not consider suspension sediment processes. We first propose a numerical scheme for the classical Saint-Venant - Exner model. It is based on a relaxation approach for the whole system and it works with all sediment flux function. The stability of the scheme is investigated and some numerical tests are proposed. We exhibit that this coupled approach is more stable than the splitting approach that is mostly used in industrial softwares. Then we derive an original three layers model in order to overcome the difficulties that are encountered when using the classical Exner approach and we present a related relaxation model. (10.1051/proc/201238005)
  DOI : 10.1051/proc/201238005
• Seasonal autoregressive modelling of skew storm surge series
  
  • Weiss Jérôme
  • Bernadara Pietro
  • Andreewsky Marc
  • Benoit Michel
  Ocean Modelling, Elsevier, 2012, 47, pp.41-54. (10.1016/j.ocemod.2012.01.005)
  DOI : 10.1016/j.ocemod.2012.01.005
• Dam-break flows over mobile beds: experiments and benchmark tests for numerical models
  
  • Soares-Frazao Sandra
  • Canelas Ricardo
  • Cao Zhixian
  • Cea Luis
  • Chaudhry Hanif
  • Die Moran Andres
  • El Kadi Kamal
  • Ferreira Rui
  • Cadorniga Ignacio
  • Gonzalez-Ramirez Noemi
  • Greco Massimo
  • Huang Wei
  • Imran Jasim
  • Le Coz Jérôme
  • Marsooli Reza
  • Paquier André
  • Pender Gareth
  • Pontillo Marianeve
  • Puertas Jeronimo
  • Spinewine Benoit
  • Swartenbroekx Catherine
  • Tsubaki Ryota
  • Villaret Catherine
  • Wu Weiming
  • Yue Zhiyuan
  • Zech Yves
  Journal of Hydraulic Research, Taylor & Francis, 2012, 50 (4), pp.364-375. In this paper, the results of a benchmark test launched within the framework of the NSF–PIRE project “Modelling of Flood Hazards and Geomorphic Impacts of Levee Breach and Dam Failure” are presented. Experiments of two-dimensional dam-break flows over a sand bed were conducted at Université catholique de Louvain, Belgium. The water level evolution at eight gauging points was measured as well as the final bed topography. Intense scour occurred close to the failed dam, while significant deposition was observed further downstream. From these experiments, a benchmark was proposed to the scientific community, consisting of blind test simulations, that is, without any prior knowledge of the measurements. Twelve different teams of modellers from eight countries participated in the study. Here, the numerical models used in this test are briefly presented. The results are commented upon, in view of evaluating the modelling capabilities and identifying the challenges that may open pathways for further research. (10.1080/00221686.2012.689682)
  DOI : 10.1080/00221686.2012.689682