Michel BENOIT

Current position

Michel BENOIT Senior scientist at EDF R&D (Electricité de France) at the Laboratoire National d’Hydraulique et Environnement (LNHE) and Saint-Venant Hydraulics Laboratory (LHSV).

Previous positions

Full Professor at Ecole Centrale Méditerranée (ECM) and Senior Researcher at IRPHE lab (Research Institute on Out-of-Equilibrium Phenomena) UMR 7342 (Aix Marseille Univ, CNRS, Ecole Centrale Méditerranée).
Head of the team Structures-Atmosphere-Ocean (SAO) (01/09/2015 – 31/08/2020)
Professor of Fluid Mechanics and Ocean Engineering at Ecole des Ponts, Marne-la-Vallée (France).
Founder and head of Saint-Venant Hydraulics Laboratory (LHSV), Université Paris Est (EDF R&D, Ecole des Ponts, Cerema) (15/01/2008 – 31/08/2015).
Research-engineer at EDF R&D LNHE (01/09/1990 – 31/08/2015)

Research activities and professional skills

Ocean and coastal waves: free surface gravity waves, wind waves and oceanic sea states, tides and storm surges, tsunamis. Wave-current-atmosphere interactions. Nonlinear wave-wave interactions. Freak waves.
Fluid mechanics for geophysical flows: river, coastal and marine hydrodynamics, physical oceanography (waves, tides, currents). Ocean hazards.
Wave-structure interaction applied to various kinds of marine and coastal structures: rubble-mound breakwaters, monopiles and floaters for offshore wind turbines, jackets, jetties, quays, seawalls, etc.
Numerical modelling of water waves, by using either phase-averaged approaches (developper of Tomawac spectral 3rd generation wave model) or phase-resolving approaches: Boussinesq and Serre-Green-Naghdi-type models, high-order spectral method (HOS), fully nonlinear potential flow solver whispers3D, etc.
Analysis and characterization of multidirectional sea states in wave basins and in the ocean.

Publications

Author or co-author of: Publications Michel BENOIT

75 journal articles
1 collective book (textbook on fluid mechanics)
8 book chapters
130+ articles in conference proceedings.
Total number of citations: 4343
(300-350 citations/year over the last 5 years).

Current H-index: 33
I10 index: 79
(Google Scholar, 12/05/2026)

Selected publications

Effect of directionality on extreme wave formation during nonlinear shoaling
- Zhang Jie
- Ma Yuxiang
- Sun Jiawen
- Huang Limin
- Benoit Michel
- Mendes Saulo
Journal of Fluid Mechanics, Cambridge University Press (CUP) , 2026, 1031, pp.R2 . Recent studies have shown that, in coastal waters where water depth decreases significantly due to rapid bathymetric changes, the non-equilibrium dynamics (NED) substantially increases the occurrence probability of extreme (rogue) waves. Nevertheless, research on depth-induced NED has been predominantly confined to unidirectional irregular waves, while the role of directionality remains largely unexplored. The scarce studies on multidirectional waves mainly rely on numerical simulations and have yielded conflicting results. In this work, we report on an experimental investigation of wave directionality on the depth-induced non-equilibrium wave statistics. High-order statistical moments, skewness and kurtosis, are used as proxies for the non-equilibrium wave response. Our results indicate that the directional spreading has a minor effect on decreasing the maximum values of these statistical moments. In contrast, the incidence direction plays a significant role in the non-equilibrium wave response, which is attributed to the effective bottom slope. (10.1017/jfm.2026.11352)
DOI : 10.1017/jfm.2026.11352
Numerical Modelling of Nearshore Wave Transformation and Overtopping with Weakly-Dispersive Wave Models
- Coulaud Guillaume
- Teles Maria
- Benoit Michel
, 2026, 42, pp.63-69 . We investigate the performance of a numerical model based on fully nonlinear depth-averaged equations for simulating wave propagation, transformation and overtopping over coastal structures. The model is based on the weakly-dispersive Serre-Green-Naghdi equations, solved with a high-order finite-volume/finite-difference scheme. Wave breaking is modelled either by locally switching to the nonlinear shallow water equations or by adding a diffusive-like term to dissipate energy, with a turbulent viscosity computed from the turbulent kinetic energy. Contrary to the former approach, the latter allows to perform computations with fine meshes, which is necessary to compute wave run-up and overtopping accurately. The model is used to reproduce experiments of solitary and irregular wave propagation, breaking, run-up and overtopping, with satisfactory results. (10.1007/978-3-032-15477-4_11)
DOI : 10.1007/978-3-032-15477-4_11
Wave overtopping of rock-armored breakwaters in bimodal long-crested sea state conditions
- Villefer Antoine
- Violeau Damien
- Teles Maria João
- Luneau Christopher
- Benoit Michel
Coastal Engineering Journal, World Scientific Publishing , 2026, pp.1-17 . The mean wave overtopping rate is an essential parameter to design coastal protections. Estimating it with a high precision is primordial to find a balance between a satisfactory safety level and a limited impact on the environment and construction costs. A series of laboratory experiments was conducted in a wave flume to estimate the wave overtopping discharge over a rock-armored breakwater in bimodal sea state conditions (combining swell and wind waves). Both simulated swell and wind wave systems were long-crested and colinear. Preliminary tests were performed on a smooth breakwater to validate the experimental set-up. Some trends in the results with the smooth slope can be characterized by the representative wave steepness. These trends are confirmed and amplified in the presence of the armor rubble slope. In that case, the measured wave overtopping rate can be significantly overestimated by existing prediction formulas, especially for sea state conditions with a high representative wave steepness, corresponding to a high wind-wave proportion in the sea state energy. We suggest two methods to take into account the effect of sea-state bimodality via the representative wave steepness to improve the wave overtopping rate estimations for smooth and armored rubble breakwaters. (10.1080/21664250.2026.2638069)
DOI : 10.1080/21664250.2026.2638069
Nonlinear statistics evolution of extreme wave fields over strongly reflective plane beaches
- Zhang Jie
- Benoit Michel
- Mendes Saulo
Ocean Engineering, Elsevier , 2026, 350, pp.124183 . The description of complex wave processes, in addition to the shoaling problem, is often cumbersome even for the evolution of regular waves. For reflection under the regime of wave breaking, the surf similarity is generally accepted as the leading parameter controlling the reflection rates and types of breakers. While little is known about the effect of reflection rates on the formation of extreme nonlinear waves, some debate has arisen regarding whether high reflection rates enhance the nonlinearity at the tail of the wave height distribution through its Gram-Charlier approximation proxies (excess kurtosis and skewness). In this work, we provide theoretical evidence that at very steep beaches of smooth composition, the reflection rate nearing unity will tend to stabilize the excess kurtosis otherwise generated by shoaling and controlled in magnitude by the bottom slope magnitude. We further verified this result through fully nonlinear numerical simulations, reaching a good agreement. (10.1016/j.oceaneng.2026.124183)
DOI : 10.1016/j.oceaneng.2026.124183
Bayesian optimization for re-analysis and calibration of extreme sea state events simulated with a spectral third-generation wave model
- Goeury Cédric
- Fouquet Thierry
- Teles Maria
- Benoit Michel
, 2026 . Accurate hindcasting of extreme sea state events is essential for coastal engineering, risk assessment, and climate studies. However, the reliability of numerical wave models remains limited by uncertainties in physical parameterizations and model inputs. This study presents a novel calibration framework based on Bayesian Optimization (BO), leveraging the Tree structured Parzen Estimator (TPE) to efficiently estimate uncertain sink term parameters, specifically bottom friction dissipation, depth induced breaking, and wave dissipation from strong opposing currents, in the ANEMOC-3 hindcast wave model. The proposed method enables joint optimization of continuous parameters and discrete model structures, significantly reducing discrepancies between model outputs and observations. Applied to a one month period encompassing multiple intense storm events along the French Atlantic coast, the calibrated model demonstrates improved agreement with buoy measurements, achieving lower bias, RMSE, and scatter index relative to the default sea-state solver configuration. The results highlight the potential of BO to automate and enhance wave model calibration, offering a scalable and flexible approach applicable to a wide range of geophysical modeling problems. Future extensions include multi-objective optimization, uncertainty quantification, and integration of additional observational datasets. (10.48550/arXiv.2601.00628)
DOI : 10.48550/arXiv.2601.00628
Resolved DEM-CFD coupling for wave-armour blocks interactions
- Barcet Matthieu
- Benguigui William
- Laviéville Jérôme
- Benoit Michel
- Wachs Anthony
- Fede Pascal
- Bonometti Thomas
Ocean Engineering, Elsevier , 2025, 337, pp.121865 . The present work aims to tackle breakwater stability challenges through an innovative numerical deterministic method using a resolved DEM-CFD (Discrete Element Method—Computational Fluid Dynamics) strategy, which simulates the individual motions of armour units within a fluid solver. To achieve this, a coupling between a DEM code and a CFD code is implemented and validated. The fluids (air and water) are solved using a Eulerian–Eulerian CFD solver, and the contacts between blocks are solved using a DEM code. The solids are defined within the fluid solver using a discrete forcing approach and are therefore fully resolved. In this way, the fluid solver enables the prediction of object motions with complex shapes such as tetrapods. To couple the codes, forces exerted on the solids are calculated in the fluid solver and sent to the DEM solver. Then, contact and gravity forces are computed and added to the fluid forces. The DEM solver then computes the new positions and velocities of the bodies, which are retrieved by the fluid solver. An experimental study is performed on a fixed and instrumented idealized breakwater to evaluate the wave forces acting on a coastal structure. The experiments are then numerically reproduced to validate the numerical model. Simulations of the impact of solitary waves on a row of mobile isolated tetrapods laid on a horizontal berm are then performed using the DEM-CFD coupling. The importance of initial placement and friction parameters is investigated to show the sensitivity to these parameters. (10.1016/j.oceaneng.2025.121865)
DOI : 10.1016/j.oceaneng.2025.121865
L'hydrodynamique des vagues du large jusqu'à la côte : modélisation et impacts
- Benoit Michel
- Harris Jeffrey
- Yates Marissa
Transitions. Les nouvelles Annales des Ponts et Chaussées, École des Ponts ParisTech et Presses des Ponts , 2025 (5), pp.44-48 .
Numerical modelling of nearshore wave transformation, breaking and overtopping of coastal protections with the enhanced Serre-Green–Naghdi equations
- Coulaud Guillaume
- Teles Maria
- Benoit Michel
Coastal Engineering, Elsevier , 2025 . Admissible average overtopping discharges in given storm conditions are typically used to design coastal protections, in particular dykes or breakwaters. These discharges are usually estimated using semi-empirical formulas relying on wave conditions at the toe of the structure. These formulas, unfortunately, only work for simple configurations, invariant alongshore, and can be insufficient for complex sea states. Therefore, numerical modelling could be a more flexible alternative for estimating these discharges. This work presents the development and validation of a Boussinesq-type numerical model solving the fully-nonlinear weakly-dispersive enhanced Serre-Green-Naghdi equations for the simulation of random wave overtopping over impermeable structures in one horizontal dimension. Wave breaking is modelled with an eddy viscosity approach based on the turbulent kinetic energy, which is robust and accurate at describing energy dissipation in the surf zone. Two distinct experimental datasets, with 184 trials in total and very dissimilar wave conditions and foreshore seabed profiles, are used to validate the model regarding wave propagation, shoaling, breaking and overtopping. Both unimodal and bimodal sea states are considered. Average overtopping discharges in configurations with deep and very shallow foreshores, as well as for breaking and non-breaking waves, are well reproduced by the model. For instance, typical mean relative errors on the simulated mean overtopping rates are found to lie within ±20% compared with the measurements, at least for the largest discharges of the considered campaigns. The scatter of simulated discharges is somewhat higher for lower discharges, but the results remain in an acceptable range. (10.1016/j.coastaleng.2025.104857)
DOI : 10.1016/j.coastaleng.2025.104857
On a high-order shallow-water wave model with canonical non-local Hamiltonian structure
- Papoutsellis Christos
- Benoit Michel
Physica D: Nonlinear Phenomena, Elsevier , 2025, 479, pp.134691 . We derive and study a new family of non-local partial differential equations (PDEs) that model free-surface long gravity waves over a flat bottom. To derive the model equations we approximate the velocity potential as a series of vertical polynomials derived from the shallow-water expansion of the Dirichlet-to-Neumann problem in the Hamiltonian formulation of free-surface potential flow and invoke Luke's variational principle. The resulting evolution equations exhibit a non-local Hamiltonian structure being coupled with a system of linear elliptic spatial PDEs on the horizontal plane. A key advantage of this approach is that it directly yields canonical Hamiltonian equations, which are well-suited for numerical solutions using standard methods. This class of model equations offers high-order shallow-water approximations of the water-wave problem. It contains terms whose spatial derivatives are at most of order two, distinguishing it from asymptotic methods involving higher-order mixed spatio-temporal derivatives. We explore the first non-trivial member of this family, highlighting its connections to other mathematical models and emphasizing its practical utility. We then analyze and discuss its linear dispersive properties and demonstrate that it does not exhibit a specific type of instability known as wave-trough instability. Additionally, we demonstrate its effectiveness in simulating the long-distance steady propagation of strongly non-linear solitary waves and the head-on collision of two counter-propagating solitary waves. In the latter case, comparisons with experimental data confirm the model's ability to capture complex wave dynamics, including wave transformation in the presence of strong non-linearity and dispersion. The extension of this approach to accommodate variable bottom topography is briefly discussed. (10.1016/j.physd.2025.134691)
DOI : 10.1016/j.physd.2025.134691
A comparison of eight weakly dispersive Boussinesq-type models for non-breaking long-wave propagation in variable water depth
- Coulaud Guillaume
- Teles Maria
- Benoit Michel
Coastal Engineering, Elsevier , 2025, 195, pp.104645 . Weakly dispersive Boussinesq-type models are extensively used to model long-wave propagation in coastal areas and their interaction with coastal infrastructures. Many equations falling in this category have been formulated during the last decades, but few detailed comparisons between them can be found in the literature. In this work, we investigate theoretically and with computational experiments eight variants of the most popular models used by the coastal engineering community. Both weakly nonlinear and fully nonlinear models are considered, hoping to understand better when the additional complexity of the latter class of models is necessary or justified. We provide an overview and discuss the properties of these models, including the linear dispersion relation in uniform water depth, the second-order nonlinear coupling coefficient, the shoaling gradient, and the sensitivity to wave trough instabilities. The models are then numerically discretised using the same general strategy in a single numerical code, using fourth-order methods for time and space discretisation. Their capacity to simulate coastal wave propagation and their transformation when approaching the shore is assessed on three challenging one-dimensional benchmarks. It appears that fully nonlinear models are more consistent than their weakly nonlinear counterparts, which can occasionally perform better but show different behaviours depending on the case. (10.1016/j.coastaleng.2024.104645)
DOI : 10.1016/j.coastaleng.2024.104645
Effect of shoaling length on rogue wave occurrence
- Zhang Jie
- Mendes Saulo
- Benoit Michel
- Kasparian Jérôme
Journal of Fluid Mechanics, Cambridge University Press (CUP) , 2024, 997, pp.A69 . The impact of shoaling on linear water waves is well known, but it has only been recently found to significantly amplify both the intensity and frequency of rogue waves in nonlinear irregular wave trains atop coastal shoals. At least qualitatively, this effect has been partially attributed to the ‘rapid’ nature of the shoaling process, i.e. shoaling occurs over a distance far shorter than that required for waves to modulate themselves and adapt to the reduced water depth. Through a theoretical model and highly accurate nonlinear simulations, we disentangle the respective effects of the length and angle of a shoal's slope. We investigate the effects of the shoaling process rapidness on the evolution of key statistical and spectral sea-state parameters. We let the wave field evolve over a slope with constant angle in all cases while we vary the slope length. Our results indicate that the non-equilibrium dynamics is not affected by the slope length, because further extending the slope length does not influence the magnitude of the statistical and spectral measures as long as the non-equilibrium dynamics dominates the wave evolution. Thus, the shoaling effect on rogue waves is deduced to be mainly driven by the slope magnitude rather than the slope length. (10.1017/jfm.2024.687)
DOI : 10.1017/jfm.2024.687
Kinematics of nonlinear waves over variable bathymetry. Part II: Statistical distributions of orbital velocities and accelerations in irregular long-crested seas
- Zhang Jie
- Ma Yuxiang
- Benoit Michel
Coastal Engineering, Elsevier , 2024, 193, pp.104589 . In coastal areas, variable bottom effects significantly enhance wave nonlinearity and complicate wave propagation. It is of practical interest to characterize the nonlinear effect on the statistics of free surface displacements and particle kinematics. In this work, we take advantage of a fully nonlinear potential flow model to investigate the statistics of unidirectional irregular waves propagating over an uneven bottom. By confronting the simulated results with existing experimental results (free surface elevation and horizontal velocity beneath the mean sea level) in the temporal, spectral, and statistical domains, we show the high fidelity of the model in predicting the nonlinear irregular wave kinematics. As the relative importance of low-frequency harmonics becomes lower for acceleration, the model performance in predicting the measured horizontal acceleration is even better than that for the measured horizontal velocity. The empirical statistical distributions of velocity and acceleration in both horizontal and vertical directions are compared with both the normal (Gaussian) and the log-normal (LN) distributions. The latter requires skewness as an input in addition to the mean and standard deviation of the signal. We notice that, unlike the free surface displacement generally of positive skewness, the signal of velocities and accelerations are sometimes characterized by negative skewness. In such cases, the negative LN distribution should be adopted. Although the LN distribution has rarely been used for short-term statistics of wave elevation and kinematics, the detailed comparisons presented here demonstrate very good performance for all kinematic variables. In particular, in the area following a rapid reduction of water depth, where the sea-state is out-of-equilibrium, the heavy tails in the distributions are well reproduced by the LN model, indicating some generality and merits of this model. (10.1016/j.coastaleng.2024.104589)
DOI : 10.1016/j.coastaleng.2024.104589
Kinematics of nonlinear waves over variable bathymetry. Part I: Numerical modelling, verification and validation
- Benoit Michel
- Zhang Jie
- Ma Yuxiang
Coastal Engineering, Elsevier , 2024, 193, pp.104577 . Fluid particle kinematics due to wave motion (i.e. orbital velocities and accelerations) at and beneath the free surface is involved in many coastal and ocean engineering applications, e.g. estimation of wave-induced forces on structures, sediment transport, etc. This work presents the formulations of these kinematics fields within a fully nonlinear potential flow (FNPF) approach. In this model, the velocity potential is approximated with a high-order polynomial expansion over the water column using an orthogonal basis of Chebyshev polynomials of the first kind. Using the same basis, original analytical expressions of the components of velocity and acceleration are derived in this work. The estimation of particle accelerations in the course of the simulation involves the time derivatives of the decomposition coefficients, which are computed with a high-order backward finite-difference scheme in time. The capability of the numerical model in computing the particle kinematics is first validated for regular nonlinear waves propagating over a flat bottom. The model is shown to be able to predict both the velocity and acceleration of highly nonlinear and nearly breaking waves with negligible error compared to the corresponding stream function wave solution. Then, for regular waves propagating over an uneven bottom (bar-type bottom profile), the simulated results are confronted with existing experimental data, and very good agreement is achieved up to the sixth-order harmonics for free surface elevation, velocity and acceleration. (10.1016/j.coastaleng.2024.104577)
DOI : 10.1016/j.coastaleng.2024.104577
Wave–structure interaction by a two–way coupling between a fully nonlinear potential flow model and a Navier–Stokes solver
- Landesman Paul
- Harris Jeffrey
- Peyrard Christophe
- Benoit Michel
Ocean Engineering, Elsevier , 2024, 308, pp.118209 . A two-way domain decomposition coupling procedure between a fully nonlinear potential flow model and a Navier–Stokes solver capturing the free surface with a Volume of Fluid method is used to study wave–structure interaction applied to offshore wind turbines. Away from the structure, the large-scale inviscid wave field is modeled by the potential code. Wave generation and absorption in this 3D hybrid model take place in the outer potential domain. The codes exchange data in the region around their common boundaries. Through the two-way coupling, waves propagate in and out of the viscous subdomain, making the hybrid algorithm suitable to study wave diffraction on marine structures, while keeping the viscous subdomain small. Each code uses its own mesh and time step. Subdomains are overlapping, therefore continuity conditions on velocity and free surface have to be verified on two distinct coupling surfaces at any time. Parallel implementation with communications between the models relying on the Message Passing Interface library allows calculations on large spatial and temporal scales. The coupling algorithm is first tested for regular nonlinear waves and then applied to simulate wave loads exerted on a vertical monopile in 3D. Attention is paid to the high-order components of the horizontal force. (10.1016/j.oceaneng.2024.118209)
DOI : 10.1016/j.oceaneng.2024.118209
Statistical distributions of free surface elevation and wave height for out-of-equilibrium sea-states provoked by strong depth variations
- Zhang Jie
- Ma Yuxiang
- Benoit Michel
Ocean Engineering, Elsevier , 2024, 293, pp.116645 . As unidirectional irregular wave trains propagate over a steep shoal, the sea-state becomes out-of-equilibrium and is continuously affected by the non-equilibrium dynamics (NED) over dozens of characteristic wavelengths. Using the set of accurate numerical simulations of Zhang et al. (2022), the NED effects on the probability distributions of free surface elevation and wave height, the statistical moments and maximum wave statistics are investigated, in both near-field and far-field regions after the water depth transition. The primary contribution of this work is to assess the applicability and limitations of several popular statistical distribution models in describing non-equilibrium statistics. In addition, a new distribution of the free surface elevation in a lognormal shape is proposed, which predicts the non-equilibrium free surface statistics with satisfactory performance and characterizes well the skewness–kurtosis relationship in the short scale. It is shown that the statistics in the far-field region are significantly influenced by the near-field wave-wave interaction, and beyond the capability of all statistical models considered here. Despite this complexity, the sea-state in the far-field region exhibits lower freak wave probability than a Gaussian sea-state. Implications of these findings for engineering practices are discussed. (10.1016/j.oceaneng.2023.116645)
DOI : 10.1016/j.oceaneng.2023.116645
Equilibration process of out-of-equilibrium sea-states induced by strong depth variation: Evolution of coastal wave spectrum and representative parameters
- Zhang Jie
- Benoit Michel
- Ma Yuxiang
, 2022, pp.104099 . Recent studies showed both experimental and numerical evidence that the occurrence probability of freak waves could be significantly enhanced as results of non-equilibrium dynamics induced by strong depth variations. The sea-state is characterized by strong non-Gaussian behavior in a short spatial extent after the depth transition, covering a few wavelengths. In this work, we investigate the complete equilibration process of an out-of-equilibrium sea-state via high-fidelity numerical simulations. In the simulations, the region after the depth transition is set as long as around one hundred wavelengths, such that the spectral adaptation develops and terminates eventually. The results are analyzed with spectral, cross-spectral and statistical approaches. It is shown that there are two stages with different spatial scales in the equilibration process. In the short scale, the sea-state is characterized by significant changes in wave statistics, freak wave occurrence probability is intensified. In the long scale, the wave spectrum undergoes strong modulation, the spectral peak disintegrate into a relative broad band, and low-frequency waves are enhanced as well. We show evidence that the spectral changes in the long scale are due to interactions of free components. The wave nonlinearity is shown to be positively correlated to the magnitude of the dynamical responses, but irrelevant to the length of the spatial scales in the equilibration process. In the established shallow-water equilibrium, the freak wave occurrence probability becomes less than Gaussian expectation and the waves are asymmetric in the vertical direction and symmetric in the horizontal. (10.1016/j.coastaleng.2022.104099)
DOI : 10.1016/j.coastaleng.2022.104099
Enhanced extreme wave statistics of irregular waves due to accelerating following current over a submerged bar
- Zhang Jie
- Ma Yuxiang
- Tan Ting
- Dong Guohai
- Benoit Michel
Journal of Fluid Mechanics, Cambridge University Press (CUP) , 2023, 954, pp.A50 . We present experimental results of irregular long-crested waves propagating over a submerged trapezoidal bar with the presence of a background current in a wave flume. We investigate the non-equilibrium phenomenon (NEP) induced by significant changes of water depth and mean horizontal flow velocity as wave trains pass over the bar. Using skewness and kurtosis as proxies, we show evidence that an accelerating following current could increase the sea-state non-Gaussianity and enhance both the magnitude and spatial extent of the NEP. We also find that below a ‘saturation relative water depth’ $k_p h_2 \approx 0.5$ ( $k_p$ being the peak wavenumber in the shallow area of depth $h_2$ ), although the NEP manifests, the decrease of the relative water depth does not further enhance the maximum skewness and kurtosis over the bar crest. This work highlights the nonlinear physics according to which a following current could provoke higher freak wave risk in coastal areas where modulation instability plays an insignificant role. (10.1017/jfm.2022.1022)
DOI : 10.1017/jfm.2022.1022
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
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
Experimental and numerical characterization of swell type waves effect on wind sea growth with fetch
- Villefer Antoine
- Benoit Michel
- Violeau Damien
- Teles Maria João
- Harris Jeffrey C.
- Branger Hubert
- Luneau Christopher
, 2021 .
Influence of swell on wind-wave growth with fetch: an experimental and numerical study
- Villefer Antoine
- Teles Maria João
- Benoit Michel
- Violeau Damien
- Harris Jeffrey C.
- Branger Hubert
, 2021 .
Comparing methods of modeling depth-induced breaking of irregular waves with a fully nonlinear potential flow approach
- Simon Bruno
- Papoutsellis Christos
- Benoit Michel
- Yates Marissa L.
Journal of Ocean Engineering and Marine Energy, Springer , 2019 . The modeling of wave breaking dissipation in coastal areas is investigated with a fully nonlinear and dispersive wave model. The wave propagation model is based on potential flow theory, which initially assumes non-overturning waves. Including the impacts of wave breaking dissipation is however possible by implementing a wave breaking initiation criterion and dissipation mechanism. Three criteria from the literature, including a geometric, kinematic, and dynamic-type criterion, are tested to determine the optimal criterion predicting the onset of wave breaking. Three wave breaking energy dissipation methods are also tested: the first two are based on the analogy of a breaking wave with a hydraulic jump, and the third one applies an eddy viscosity dissipative term. Numerical simulations are performed using combinations of the three breaking onset criteria and three dissipation methods. The simulation results are compared to observations from four laboratory experiments of regular and irregular waves breaking over a submerged bar, irregular waves breaking on a beach, and irregular waves breaking over a submerged slope. The different breaking approaches provide similar results after proper calibration. The wave transformation observed in the experiments is reproduced well, with better results for the case of regular waves than irregular waves. Moreover, the wave statistics and wave spectra are predicted well in general, and in particular for regular waves. Some differences are observed for irregular wave cases, in particular in the low-frequency range. This is attributed to incomplete absorption of the long waves in the numerical model. Otherwise, the wave spectra in the range [0.5fp, 5fp] are reproduced well, before, inside, and after the breaking zone for the three irregular wave experiments. (10.1007/s40722-019-00154-7)
DOI : 10.1007/s40722-019-00154-7
Modelling of depth-induced wave breaking in a fully nonlinear free-surface potential flow model
- Papoutsellis Christos
- Yates Marissa L.
- Simon Bruno
- Benoit Michel
Coastal Engineering, Elsevier , 2019, 154, pp.103579 . (10.1016/j.coastaleng.2019.103579)
DOI : 10.1016/j.coastaleng.2019.103579
Development and validation of a 3D RBF-spectral model for coastal wave simulation
- Raoult Cécile
- Benoit Michel
- Yates Marissa L.
Journal of Computational Physics, Elsevier , 2019, 378, pp.278-302 . With the objective of simulating wave propagation in the nearshore zone for engineering-scale applications, a two dimensional (2DV) model based on the Euler-Zakharov equations (Yates and Benoit, 2015; Raoult et al., 2016) is extended to three dimensions (3D). To maintain the flexibility of the approach with the goal of applying the model to irregularly shaped domains, the horizontal plane is discretized with scattered nodes. The horizontal derivatives are then estimated using the Radial Basis Function-Finite Difference (RBF-FD) method, while a spectral approach is used in the vertical dimension. A sensitivity analysis examined the robustness of the RBF-FD approach as a function of RBF parameters when estimating the derivatives of a representative function. For a targeted stencil size between 20 and 30 nodes, Piecewise-Smooth (PS) polyharmonic spline (PHS) functions are recommended, avoiding the use of Infinitely-Smooth (IS) RBFs, which are less appropriate for the desired applications because of their dependence on a shape parameter. Comparisons of simulation results to observations from two wave basin experiments show that nonlinear effects induced by complex bottom bathymetries (10.1016/j.jcp.2018.11.002)
DOI : 10.1016/j.jcp.2018.11.002
A 3D parallel boundary element method on unstructured triangular grids for fully nonlinear wave-body interactions
- Dombre E.
- Harris J.C.
- Benoit Michel
- Violeau D.
- Peyrard C.
Ocean Engineering, Elsevier , 2019, 171, pp.505-518 . This paper presents the development and validation of a three-dimensional numerical wave tank devoted to studying wave-structure interaction problems. It is based on the fully nonlinear potential flow theory, here solved by a boundary element approach and using unstructured triangular meshes of the domain's boundaries. Time updating is based on a second-order explicit Taylor series expansion. The method is parallelized using the Message Passing Interface (MPI) in order to take advantage of multi-processor systems. For radiation problems, with cylindrical bodies moving in prescribed motion, the free-surface is updated with a fully Lagrangian scheme, and is able to reproduce reference results for nonlinear forces exerted on the moving body. For diffraction problems, semi-Lagrangian time-updating is used, and reproduces nonlinear effects for diffraction on monopiles. Finally, we study the nonlinear wave loads on a fixed semi-submersible structure, thereby illustrating the possibility to apply the proposed numerical model for the design of offshore structures and floaters. (10.1016/j.oceaneng.2018.09.044)
DOI : 10.1016/j.oceaneng.2018.09.044