Publications

2022

• Simulation of wave-structure interaction by a two-way coupling between a fully nonlinear potential flow model and a Navier-Stokes solver
  
  • Landesman Paul
  , 2022. This thesis deals with the development and application of a two-way coupling procedure between a fully nonlinear potential flow model and a Navier-Stokes solver to study wave-structure interaction applied to offshore wind turbines. The coupling strategy relies on a domain decomposition method, in which the wave fieldclose to the structure of interest is simulated with the Navier-Stokes solver Code Saturne,an open-source Finite Volume code capturing the free surface with a Volume of Fluidmethod. Away from the structure, where viscous and turbulent effects may be neglected, the potential code, solving the Laplace equation for the velocity potential with a boundaryintegral formulation, is applied to model the large scale wave field.Generation and absorption of waves in this three-dimensional hybrid numerical wave tanktake place in the outer potential domain. The potential and Navier-Stokes codes exchange data in the region around their common boundaries. The coupling may thus be referredto as “two-way”, enabling one to propagate waves in and out of the viscous subdomain, and making the hybrid algorithm suitable to study wave diffraction on fixed offshore windturbines, while keeping the viscous subdomain as small as possible. Each code uses its own mesh and time step. Subdomains are overlapping, therefore a velocity continuity conditionand a free surface continuity condition have to be verified on two distinct coupling surfacesat any time.Parallel implementation of the coupling strategy with communications between the modelsrelying on the Message Passing Interface (MPI) library allows calculations to be run onlarge spatial and temporal scales on distributed memory clusters. The coupling algorithmis tested for various incident wave conditions, including solitary waves and regular nonlinear waves. It is then applied to the simulation of wave loads exerted on a vertical monopileand numerical results are compared with experimental measurements performed in a waveflume considering various values of the period and steepness of incident waves. Attention is paid to the analysis of high-order components of the nonlinear horizontal force.
• Unified depth-limited wave breaking detection and dissipation in fully nonlinear potential flow models
  
  • Mohanlal Sunil
  • Harris Jeffrey
  • Yates Marissa
  • Grilli Stephan
  , 2022. A new method is proposed for simulating the energy dissipation resulting from depth-limited wave breaking, in combination with a universal breaking onset criterion, in two-dimensional (2D) fully nonlinear potential flow (FNPF) models, based on a non-dimensional breaking strength parameter. Two different 2D-FNPF models are used, which solve the Laplace equation based on Chebyshev polynomial expansions or a boundary element method. In these models, impending breaking waves are detected in real time using a universal breaking onset criterion proposed in earlier work, based on the ratio of the horizontal particle velocity at the crest u, relative to the crest velocity c, B = u/c > 0.85. For these waves wave energy is dissipated locally using an absorbing surface pressure that is calibrated using an inverted hydraulic jump analog. This approach is first validated for periodic spilling breakers over plane beaches and bars, for which results are shown to be in good agreement with experimental data. Recasting this breaking dissipation model in terms of a non-dimensional breaking strength, the hydraulic jump analog is shown to provide results similar to those of a constant breaking strength model, and to yield good agreement for periodic plunging breakers as well. The same approach is then applied to irregular waves shoaling over a submerged bar, and shown to agree well with experimental data for the wave height, asymmetry, skewness, and kurtosis. Future work will extend this 2D breaker model to cases of three-dimensional (3D) breaking waves, simulated in existing 3D-FNPF models, in shallow or deep water conditions.
• Sensitivity of a one-line longshore shoreline change model to the mean wave direction
  
  • Chataigner T.
  • Yates Marissa L.
  • Le Dantec N.
  • Harley M.D.
  • Splinter K.D.
  • Goutal N.
  Coastal Engineering, Elsevier, 2022, 172, pp.104025. (10.1016/j.coastaleng.2021.104025)
  DOI : 10.1016/j.coastaleng.2021.104025
• Real time instability of flow close to a scour affected abutment
  
  • Chevalier Christophe
  • Larrarte Frédérique
  Environmental Fluid Mechanics, Springer Verlag, 2022, 22, pp.495–510. For centuries, the interaction between the transport and hydrographic networks represents a signifcant issue in a country such as France. For example, the French railway network includes 1700 river-crossing structures and an important length of embankments either forming river banks or adjacent to watercourses exposed to scouring processes. Recently, various cases highlight the importance and vulnerability of civil transport works in relation to their environmental hazards, e.g. foods, and therefore the need to develop integrated observation tools and warning systems in the aim both of optimizing the management system and of increasing the knowledge on real scour processes. This paper relies to a French research project named SSHEAR which objective is to improve understanding of the scouring process through the use of innovative observation tools and physical and numerical hydraulic modelling. This part of the project aims at improving continuous monitoring in order to follow the evolution of the scour processes of a given bridge or abutment. After a presentation of the experimental site, the instrumentation is described as well as its in situ implementation. The data analysis process is given and results are commented before the presentation of some perspectives part. (10.1007/s10652-022-09842-9)
  DOI : 10.1007/s10652-022-09842-9
• Hybrid simulation of turbulent flow interactions with submerged structures by combining a potential flow solver and a Lattice-Boltzmann LES model
  
  • O'Reilly Christopher M
  • Grilli Stephan T
  • Janssen Christian F
  • Dahl Jason M
  • Harris Jeffrey C.
  , 2022. We develop a 3D Lattice Boltzmann Method (LBM) with Large Eddy Simulation (LES), and a wall model, to simulate interactions of fully turbulent flows with ocean structures. The LBM is based on a hybrid method, combining inviscid (far-field) and viscous (near-field) perturbation flows. The inviscid flow is solved with potential flow theory. The near-field perturbation flow, which satisfies perturbation Navier- Stokes (NS) equations, is solved with a novel perturbation LBM model (pLBM), based on a collision operator using perturbation equilibrium distribution functions (DFs). The pLBM, previously applied to direct NS modeling (DNS) is extended to highly turbulent flows using a LES, and a wall model representing viscous/turbulent sub-layer near solid boundaries. The pLBM is first validated for turbulent channel flows, for moderate to large Reynolds numbers, Re in [3.7 x 10^4; 1.2 x 10^6], and we find the modeled plate friction coefficient and near-field turbulence properties agree well with both experiments and DNS results. We then simulate the flow past a NACA-0012 foil using both a regular LBM-LES and the pLBM-LES models, for Re = 1.44 X 10^6. A good agreement with experiments and results of other numerical methods is found for the computed lift and drag forces, and pressure distribution on the foil. The pLBM results are either nearly identical or slightly improved, relative to LBM results, but are obtained with a significantly smaller computational domain and hence computing cost, thus demonstrating the benefits of the new hybrid approach.
• Three-dimensional hydrodynamic model of the Rance estuary (France) influenced by the world’s second largest tidal power plant
  
  • Rtimi Rajae
  • Sottolichio Aldo
  • Tassi Pablo
  • Bertier Christine
  • Le Brun Matthieu
  • Vandenhove Marine
  • Parquet Luca
  LHB Hydroscience Journal, Taylor & Francis Group, 2022, 108 (1). (10.1080/27678490.2021.2016025)
  DOI : 10.1080/27678490.2021.2016025
• Assessment of one-way coupling methods from a potential to a viscous flow solver based on domain- and functional-decomposition for fixed submerged bodies in nonlinear waves
  
  • Robaux Fabien
  • Benoit Michel
  European Journal of Mechanics - B/Fluids, Elsevier, 2022, 95, pp.315-334. To simulate the interaction of ocean waves with marine structures, coupling approaches between a potential flow model and a viscous model are investigated. The first model is a fully nonlinear potential flow (FNPF) model based on the Harmonic Polynomial Cell (HPC) method, which is highly accurate and best suited for representing long distance wave propagation. The second model is a CFD code, solving the Reynolds-Averaged Navier-Stokes (RANS) equations within the \openfoam toolkit, more suited to represent viscous and turbulent effects at local scale in the body vicinity. Two one-way coupling strategies are developed and compared in two dimensions, considering fully submerged and fixed structures. A domain decomposition (DD) strategy is first considered, introducing a refined mesh in the body vicinity on which the RANS equations are solved. Boundary conditions and interpolation operators from the FNPF results are developed in order to enforce values at its outer boundary. The second coupling strategy considers a decomposition of variables (functional decomposition, FD) on the local grid. As the FNPF simulation provides fields of variables satisfying the irrotational Euler equations, complementary velocity and pressure components are introduced as the difference between the total flow variables and the potential ones. Those complementary variables are solutions of modified RANS equations. Extensive comparisons are presented for nonlinear waves interacting with a horizontal cylinder of rectangular cross-section. The loads exerted on the body computed from the four simulation methods (standalone FNPF, standalone CFD, DD and FD coupling schemes) are compared with experimental data. It is shown that both coupling approaches produce an accurate representation of the loads and associated hydrodynamic coefficients (inertia and drag) over a large range of incident wave steepness and Keulegan-Carpenter number, for a small fraction of the computational time needed by the complete CFD simulation. (10.1016/j.euromechflu.2022.05.011)
  DOI : 10.1016/j.euromechflu.2022.05.011
• A new methodology for the assessment of flood hazard in urban areas due to levee breaches
  
  • Bacchi Vito
  • Goeury Cédric
  • Zaoui Fabrice
  • El Kadi Abderrezzak Kamal
  • Bacchi Sophie
  • Pavan Sara
  , 2022, pp.6672-6679. The objective of this study is to propose a new methodology for the assessment of flood hazard induced by the formation of levee breaches due to overtopping flows. The proposed methodology relies on the definition of a new breach model and on the flood hazard assessment (i.e. water height in area of interest) through a deterministic simulation. The methodology is implemented in the open-source hydrodynamic suite of solvers TELEMAC-MASCARET (www.opentelemac.org) and applied to the Loire river using the two-dimensional (2D) depth-averaged hydrodynamic code TELEMAC-2D. We chose a flood scenario corresponding to a return period of around 500 years and we compared results to those obtained by performing 3,000 Monte-Carlo simulations using uniform distribution of the model parameters. Results suggest that the deterministic simulation should be completed by a set of well-chosen deterministic scenarios in order to cover the large uncertainty showed by the computational costly Monte-Carlo simulations. (10.3850/IAHR-39WC2521711920221210)
  DOI : 10.3850/IAHR-39WC2521711920221210
• Comparer les tempêtes sur le temps long en quantifiant les dommages : proposition d’un nouvel outil
  
  • Athimon Emmanuelle
  • Maanan Mohamed
  • Pouzet Pierre
  Bulletin de l'Association de géographes français, Association de Géographes Français, 2022, 98 (3/4), pp.402-420. De nombreuses démarches d’évaluation et de classification des tempêtes de latitudes moyennes récentes ou passées existent. Aucune ne fait cependant consensus et des critiques importantes peuvent leur être adressées. En outre, la difficulté d’étudier les tempêtes en tant que telles avant la seconde moitié du XXe siècle et l’adoption de moyens d’analyse atmosphérique sophistiqués justifie de travailler à l’établissement d’un nouvel outil capable d’engager la comparaison entre tempêtes passées et actuelles. Cette recherche propose a) une nouvelle approche de quantification des dommages générés par les tempêtes des XIVe-XVIIIe siècles, b) une mise en application avec discussion des limites, c) une réflexion sur la construction d’un prototype d’évaluation des tempêtes à travers la théorisation d’une échelle d’intensité. En combinant l’estimation de l’importance des dégâts et le cadre spatial, la démarche permet notamment d’affecter un codage « pondéré » qui réduit les risques de sur ou sous-interprétation. Appliqué pour des tempêtes et submersions marines survenues dans l’ouest de la France aux XIVe-XVIIIe siècles, l’indicateur d’évaluation de l’intensité a été pensé pour être modulable et adaptable à plus grande échelle spatiale et temporelle (10.4000/bagf.8308)
  DOI : 10.4000/bagf.8308
• Nonlinear time-domain wave-structure interaction: a parallel fast integral equation approach
  
  • Harris Jeffrey C
  • Dombre Emmanuel
  • Benoit Michel
  • Grilli Stephan T.
  • Kuznetsov Konstantin I
  International Journal for Numerical Methods in Fluids, Wiley, 2022, 94, pp.188-222. We report on the development and validation of a new Numerical Wave Tank (NWT) solving fully nonlinear potential flow (FNPF) equations, as a more efficient variation of Grilli et al.'s NWT [Grilli et al., A fully nonlinear model for three-dimensional overturning waves over arbitrary bottom, International Journal for Numerical Methods in Fluids 35 (2001) 829-867], which was successful at modeling many wave phenomena, including landslide-generated tsunamis, rogue waves, and the initiation (10.1002/fld.5051)
  DOI : 10.1002/fld.5051
• Géohistoire des tempêtes et submersions marines depuis 1 000 ans : quelles interprétations climatiques dans l’ouest de la France ?
  
  • Pouzet Pierre
  • Athimon Emmanuelle
  • Maanan Mohamed
  Bulletin de l'Association de géographes français, Association de Géographes Français, 2022, 98 (3/4), pp.348-365. Dans le contexte actuel lié au changement climatique, l’étude des risques côtiers implique la considération des fluctuations historiques de l’aléa pour comprendre les paramètres océano-climatiques guidant sa variabilité. Grâce au couplage entre données sédimentologiques et historiques, quinze tempêtes intenses ont été extraites d’un carottage prélevé aux Traicts du Croisic, tandis que 128 évènements impactant ont été recensés par les sources historiques durant le dernier millénaire. La synthèse des travaux sédimentologiques et historiques réalisée dans l’ouest de la France met en lumière trois périodes tempétueuses communes estimées à environ 1330 – 1360 ap. J.-C., 1570 – 1620 ap. J.-C. et 1690 – 1720 ap. J.-C. Ces trois périodes s’inscrivent durant des phases de péjoration climatique, ou de tendance froide. Si l’activité tempétueuse semble être accrue durant les phases positives d’Oscillation Nord Atlantique (ONA), aucune corrélation stricte n’est établie. La variation de position du “rail des dépressions” expliquerait également certaines trajectoires. Pour relativiser ces résultats et proposer de nouvelles perspectives pour améliorer la gestion des risques côtiers en France, les limites de cette étude sont également discutées. Cette approche doit notamment gagner en exhaustivité pour préciser la chronologie tempétueuse, mais également l’étendre sur la totalité de la façade atlantique française et ainsi considérer l’ensemble des mécanismes susceptibles de guider leur formation en Europe de l’Ouest. (10.4000/bagf.8168)
  DOI : 10.4000/bagf.8168
• Submersions marines sur le littoral atlantique français : 700 ans d’archives sociétales et environnementales pour une meilleure connaissance et gestion du risque
  
  • Maanan Mohamed
  • Athimon Emmanuelle
  • Pouzet Pierre
  Bulletin de l'Association de géographes français, Association de Géographes Français, 2022, 98 (3/4), pp.366-384. Cette recherche, financée par la Fondation de France, avait pour objectifs :1) de retracer l’histoire des submersions marines dans l’ouest de la France à l’aided’approches pluridisciplinaires, 2) d’évaluer les impacts quantitatifs et qualitatifs deces évènements sur les sociétés littorales, et 3) de définir la notion de « résiliencesociétale » sous le prisme historique. La méthodologie repose sur une approcheinterdisciplinaire intégrant la sédimentologie (21 carottes sédimentaires ont étéprélevées) et l’histoire du climat (19 691 documents historiques ont été dépouillés etanalysés). Le cadre spatio-temporel de l'étude sur la façade atlantique française etcouvre une période allant du XIVe siècle à nos jours. Le couplage des donnéessédimentologiques avec les archives historiques a permis de caractériser quinzetempêtes avec submersions marines. Les résultats de cette recherche témoignent del’adaptabilité des populations et de leur tolérance au risque de submersion marine àtravers l’histoire. Ces différentes approches permettent d’accroître la connaissance desaléas côtiers, de contribuer à leur prévention et de proposer des outils prospectifs pourla gestion des risques littoraux. (10.4000/bagf.8226)
  DOI : 10.4000/bagf.8226