Publications

2026

• 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
• The contribution of sensitivity analysis and data assimilation to tidal-stream resource assessment: The example of the Alderney Race
  
  • Thiébot Jérôme
  • Goeury Cédric
  • Travert Jean-Paul
  • Sebastian Anju
  • Salomon Julien
  Applied Ocean Research, Elsevier, 2026, 168. Highly accurate modeling of tidal current is crucial in the assessment of tidal-stream resource. We use a method for refining the predictions of a two-dimensional tidal model applied to estimate the resource of the Alderney Race (English Channel). The first phase consists in identifying the input parameters which have the greatest influence on the model’s performance. The sensitivity analysis relies on the Sobol’ indices. It is found that the adjustment of the phase of the M₂ (lunar semidiurnal) constituent is the most efficient way to reduce model’s errors. Bottom friction and amplitudes of M₂ and S₂ (solar semidiurnal) are also influential on model performance. The second phase relies on data assimilation. The 3DVar algorithm is used to adjust the calibration parameters so that they reduce the errors between model predictions and depth-averaged current speed measured by ADCPs. The method, although common in other coastal engineering applications, is tested in the context of estimating tidal resource. It gives promising results as it reduces root mean square errors in current speed by 19%. This corresponds to a reduction of root mean square error in power density of 31% at the ADCP locations. By comparing maps of power density before and after the model calibration, we show that the adjustment of model parameters significantly modifies the resource assessment in the Alderney Race. (10.1016/j.apor.2026.104970)
  DOI : 10.1016/j.apor.2026.104970
• 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
• SPH modelling of water flow inside a fixed and undeformable porous medium using a Riemann based formulation
  
  • de Sousa Coline
  • Lallemand Marin
  • Oger Guillaume
  • Michel Julien
  • Le Touzé David
  • Violeau Damien
  Journal of Computational Physics, Elsevier, 2026, 549, pp.114588. A weakly-compressible Smoothed Particle Hydrodynamics (SPH) model for the simulation of water seepage in a fixed and undeformable porous matrix is proposed in this paper. Within this model, the macroscopic governing equations of mass and momentum are expressed using an averaging process on an elementary volume of porous medium. A first set of particles is used for modelling the fluid, while a second one is employed for the porous structure to compute the volume fraction involved in the volume-averaged equations. The stabilization of the fluid model, based on a Riemann solver, is free of any diffusion parameter and results in regular and accurate pressure fields. Moreover, a Boundary Integral Method is chosen in this work to handle wall boundary conditions, with use of the so-called Español and Revenga laplacian operator. To the authors’ knowledge, both this stabilization and wall treatment technique have never been applied yet to this field of application. The validation of the present model on three test-cases demonstrates its strong reliability, showing good agreement with numerical and experimental results from the literature. (10.1016/j.jcp.2025.114588)
  DOI : 10.1016/j.jcp.2025.114588
• Stroke rate and arm coordination management in swimming in a double Paralympic triathlete champion
  
  • Seifert Ludovic
  • Guignard Brice
  • Létocart Adrien
  • Regaieg Mohamed Amin
  • Guimard Alexandre
  • Chollet Didier
  • Carmigniani Rémi Arthur
  • Pouleau Nicolas
  • Charentus Arnaud
  • Leprêtre Pierre-Marie
  Journal of Sports Science and Medicine, University of Uludag, 2026 (25), pp.211-220. The 2024 Paris Paralympic triathlon required swimming with and against the current which requested to adapt stroke mechanics. To understand how a Paralympic triathlete champion might adapt his stroke mechanics under varying current conditions, this study aimed to 1) determine the range and optimal stroke rate (SR) and index of coordination (IdC); 2) examine the flexibility of SR, IdC and associated total energy expenditure. The para triathlete performed two front crawl tests: 10 times 25m incremented in swimming speed (S), from which S-SR and S-IdC relationships have been modelled to detect two regimes of functioning and the most effective SR; then, 6 times 50 m at the speed of the 800 m freestyle using 6 different SR conditions: spontaneous SR (SR_s), SR_s imposed by tempo trainer, SR_s+3, SR_s+6, SR_s-3 and SR_s-6 cycles. Total energy expenditure was computed from post-exercise oxygen uptake and blood lactate measurements. In test 1, the highest effective SR equals 44 cycle.min^-1, which corresponds to the preferred SR in 800 m freestyle competition. In test 2, the para triathlete struggled to perform the high SR conditions, which was associated to higher total energy expenditure; conversely, the para triathlete naturally decreased SR. It is advised to modulate SR around the preferred SR to optimise efficiency under varying current conditions. (10.52082/jssm.2026.211)
  DOI : 10.52082/jssm.2026.211
• Monitoring of Riverine Aquatic Vegetation Using Satellite PlanetScope Imagery: Feasibility, Limitations and Prospects
  
  • Rasse Léo
  • Godfroy Julien
  • Nogaro Géraldine
  • Cordier Florian
  • Feldis Danaë
  • Meunier Sophie
  • Puijalon Sara
  • Piégay Hervé
  Ecohydrology, Wiley, 2026, 19 (1), pp.E70178. Spectral interference induced by the water and the spatial resolution of many satellite images (≥ 10 m) limit the efficiency of remote sensing for monitoring riverine aquatic plant stands. In this study, the potential of using PlanetScope satellite images (3 m in spatial resolution, ~daily acquisition) for monitoring seasonal and interannual aquatic vegetation surface area was evaluated. Airborne images (≤ 0.2 m) acquired on four dates on three aquatic plant stands were used to create, through visual interpretation, reference maps indicating whether the pixels of each PlanetScope image acquired at ±8 days correspond to aquatic vegetation or nonvegetated aquatic areas. For each PlanetScope image, the green normalized difference vegetation index (GNDVI) was calculated and centred on the mean (GNDVI centred ) to distinguish aquatic vegetation from nonvegetated aquatic areas while minimizing variations in their spectral signature over time. Reference maps from the date when aquatic vegetation was the least developed were used to calculate the GNDVI centred classification threshold. To reduce classification errors from radiometric inconsistencies, the frequency at which pixels of PlanetScope images acquired at ±8 days from airborne images were classified as aquatic vegetation was also calculated. Aquatic vegetation was then empirically defined as pixels with a frequency ≥ 85%. Although the classification of PlanetScope images indicates that low abundances of aquatic vegetation cannot be detected, our results show that large changes in stand surface area can be monitored using a multidate classification threshold, thus providing new opportunities for the monitoring of riverine aquatic vegetation on large scales. (10.1002/eco.70178)
  DOI : 10.1002/eco.70178
• 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