Publications

2026

• Multi-material flow with a new viscoelastic model
  
  • Boyaval Sébastien
  , 2026. We study a new quasilinear system of balance laws (i.e. conservative first-order PDEs with source terms) for the numerical simulation by a front-capturing approach of viscoelastic athermal multi-material flows with sharp interfaces (like a mixture of immiscible fluids and solids). It naturally extends with an energy balance that is meaningful to stability and thermodynamics. In particular, the unequivocal definition of solutions to Cauchy problems can be guaranteed in some cases, thanks to a symmetric-hyperbolic formulation.
• Recovery of directional wave spectrum from sparse data with compressed sensing
  
  • Jiang Qingyu
  • Kalisch Henrik
  • Benoit Michel
  • Holand Karoline
  • Sprenger Patrick
  Frontiers in Marine Science, Frontiers Media, 2026, 13. Compressed sensing provides an efficient framework for reconstructing wave signals from reduced measurements. For multi-channel buoy data, the three displacement components exhibit intrinsic correlations, as wave motion contributes simultaneously to all directions according to linear wave theory. Meanwhile, conventional compressed sensing methods based on ℓ 1 -shrinkage tend to underestimate signal energy when sparsity is not strictly satisfied, leading to biased spectral estimation. This paper introduces a group sparsity constraint to promote joint sparse spectral representations across channels. An energy constraint is proposed in the form of a soft lower bound, enabling an isotropic rescaling of the recovered spectrum while preserving its sparse structure. The resulting model is solved using the alternating direction method of multipliers. Experiments with multi-channel buoy records indicate that the main spectral features can be recovered under the tested conditions, although weak spurious peaks may appear in the estimated directional spectra and reconstruction across long contiguous gaps remains challenging. These results suggest that the proposed approach can enable data compression by retaining a subset of the original measurements. (10.3389/fmars.2026.1909682)
  DOI : 10.3389/fmars.2026.1909682
• Predicting microbiological contamination in urban rivers: an event-based indicator approach applied to the Seine river during the 2024 Paris olympic and paralympic games
  
  • Guillot - Le Goff Arthur
  • Cartier Yoann
  • Vinçon-Leite Brigitte
  • Boyaval Sébastien
  • Carmigniani Rémi
  Journal of Hydrology, Elsevier, 2026, 674, pp.135504. Urban rivers are subject to microbiological contamination following the discharge of wastewater after heavy rains. These peaks of faecal contamination lead to health risks, particularly in urban bathing areas. To prevent these risks, European legislation requires early warning systems to be operated. This study proposes a new methodology for implementing an early warning system based on high-frequency measurements of bacteriological contamina tion proxies and hydro-meteorological data. By analysing these high-frequency data collected over three summer seasons (2021-2023) in the Seine River, Paris, France, the proposed framework defines rainfall events and their impact on microbial water quality. Dimensionality reduction techniques, including Principal Component Analysis (PCA) and Manifold ISOMAP, are applied and compared to identify key explanatory characteristics and build a predictive model. A global rain parameter (GRP) is derived, which effectively classifies rainfall events based on their potential impact on water quality. The method was successfully tested during the 2024 Paris Olympic and Paralympic Games, demonstrating its potential for real-time water quality management. (10.1016/j.jhydrol.2026.135504)
  DOI : 10.1016/j.jhydrol.2026.135504
• Automatic calibration and simultaneous estimation of bottom friction and open boundary conditions in a tidal model
  
  • Sebastian Anju
  • Thiébot Jérôme
  • Goeury Cédric
  • Travert Jean-Paul
  • Poizot Emmanuel
  • Gregoire Gwendoline
  Applied Ocean Research, Elsevier, 2026, 173, pp.105145. Data assimilation for parameter estimation in the context of coastal models generally utilises traditional variational or stochastic methods. While these methods are well established and effective in coastal applications, they often rely on gradient information and may suffer from convergence to local minima in highly nonlinear systems with larger parameter sets. In contrast, global optimisation techniques have gained increasing attention due to their ability to explore complex, multimodal and high-dimensional parameter spaces without requiring derivative information. In this paper, we explored the efficiency of a global optimisation method called Particle Swarm Optimisation within a data assimilation framework for the simultaneous estimation of bottom friction and boundary condition control parameters in a tidal model. The results from the twin experiments show that the method is efficient for parameter estimation without the need to remove the less sensitive parameters through sensitivity analysis. The method is also compared to a variational method to confirm this applicability. The optimal parameters from the calibration have been used to validate the model predictions at independent observation points, improving the predictions even in non-assimilated areas. Furthermore, with the assimilation of real data, joint estimation of calibration parameters with spatially varying bottom friction and correction in the amplitude and phase of the predominant tidal constituents lead to more accurate predictions of water elevation from the model. (10.1016/j.apor.2026.105145)
  DOI : 10.1016/j.apor.2026.105145
• Experimental Validation of an Enhanced Serre–Green–Naghdi Model for Wave Transformation and Breaking in the Nearshore Zone
  
  • Coulaud Guillaume
  • Teles Maria
  • Benoit Michel
  Water Waves, Springer, 2026. A one-dimensional numerical model based on enhanced Serre-Green-Naghdi equations is presented and validated against a broad set of laboratory experiments of nearshore wave transformation, breaking and run-up on slopes. The model uses a hybrid finite volume/finite difference numerical scheme with high-order MUSCL-type reconstructions, a hydrostatic reconstruction for well-balancedness and positivity of the water depth, and a third-order strongstability-preserving Runge-Kutta time integration. Wave breaking is modelled via an eddy viscosity approach based on a depth-integrated one-equation turbulence model for the turbulent kinetic energy. The model is validated against five sets of laboratory experiments covering the shoaling, breaking and run-up of different types of waves: solitary, regular and irregular waves. Bed profiles with gentle or mild plane slopes, as well as steep fringing reef profiles, are considered. The validation dataset encompasses both spilling and plunging breaker types. The model demonstrates its ability to accurately reproduce not only detailed wave characteristics (wave shoaling, breaking point location, spectrum transformation, wave height decay in the surf zone, nonlinear wave shape statistics and high-order statistical moments of the free surface elevation), but also the variations of the mean water level (wave set-down and set-up), the generation and propagation of infragravity waves and the run-up on the beach slope. (10.1007/s42286-026-00148-7)
  DOI : 10.1007/s42286-026-00148-7
• Dedicated VPP for Olympic Windfoil to Assess the Impact of Athlete Morphology
  
  • Hochhausen Martin
  • Sacher Matthieu
  • Augier Benoît
  • Bot Patrick
  • Carmigniani Rémi Arthur
  • Odier Philippe
  • Cohen Caroline
  , 2026, pp.265. Debuting as a new discipline at the 2024 Olympics in Marseille, the IQFoil has revolutionized windsurfing with its high-speed, hydrofoil-equipped boards that “fly” above the water. This technological evolution has forced athletes to rethink their approach to training and competition, with weight playing a crucial role in performance. Many have deliberately increased their body mass to improve stability and maintain high speeds in varying wind conditions. This strategic adaptation underscores the complexity of the sport, where aerodynamics, hydrodynamics, and physical strength must be finely balanced to achieve maximum speed and e!ciency. Using an optimized Velocity Prediction Program (VPP), the present study reveals the advantage of taller, heavier riders and explores strategies for lighter athletes to compensate, such as increasing counter-heel of the board and reducing sail counter-heel.
• Coupled CFD–DEM modelling of damage to a breakwater armour layer made of Antifer cubes exposed to regular waves
  
  • Barcet Matthieu
  • Benguigui William
  • Laviéville Jérome
  • Benoit Michel
  • Fede Pascal
  • Bonometti Thomas
  Ocean Engineering, Elsevier, 2026, 363, pp.126525. The study aims to demonstrate the capabilities of a CFD-DEM (Computational Fluid Dynamics -Discrete Element Method) to predict wave-structure interactions and armour units motions in a breakwater composed of Antifer cubes. To do so, the fluids (air and water) are simulated using a Eulerian-Eulerian CFD solver and the contacts between the blocks and the slope are solved using a DEM code. The codes were coupled and validated in a previous study, using idealised configurations that did not reflect actual coastal structures. This work extends the previous study to a semi-realistic configuration where the blocks are positioned along a inclined wall to represent the armour layer of a rubble-mound breakwater. Both experiments and simulations are performed, and the results are compared to evaluate the accuracy of the model. The comparisons are made on the number of displaced armour units and on the amplitude of their displacement.<p>Two regular configurations are studied: a one-layer configuration and a two-layers configuration which improves the stability and better represents realistic breakwaters. Finally, simulations are performed on a randomly generated armour layer which the goal of improving the realism of the breakwater.</p> (10.1016/j.oceaneng.2026.126525)
  DOI : 10.1016/j.oceaneng.2026.126525
• Bayesian Optimization for reanalysis and calibration of highly energetic sea state events simulated with a spectral third-generation wave model
  
  • Goeury Cédric
  • Fouquet Thierry
  • Teles Maria
  • Benoit Michel
  Applied Ocean Research, Elsevier, 2026, pp.105144. Accurate hindcasting of sea state events is a cornerstone of coastal engineering, risk assessment, and climate-related studies, yet it remains limited by uncertainties in physical parameterizations and model structure. This study introduces an automated calibration framework based on Bayesian Optimization (BO) using the Tree-structured Parzen Estimator (TPE) to constrain key dissipative processes in the ANEMOC-3 hindcast wave model, including bottom-friction losses, depth-induced wave breaking, and dissipation driven by wave strong opposing currents. The methodology enables the joint optimization of continuous physical parameters and discrete model structure choices within a unified probabilistic search space, significantly reducing model–observation misfit. Calibration is conducted over the high energy storm conditions of February 2014, while transferability is assessed both temporally and spatially, through independent validation on January 2014 and January 2018 events and across a network of offshore and coastal buoy observations. The optimized configurations retain skill beyond the calibration period and across observation sites, yielding systematically improved agreement with buoy measurements in terms of bias, root mean square error, and scatter index relative to the reference configuration. These results highlight the potential of Bayesian Optimization as a scalable and robust framework for automating the calibration of complex wave hindcast systems. Future developments will address multi-objective optimization, uncertainty quantification, and the integration of complementary observational datasets. (10.1016/j.apor.2026.105144)
  DOI : 10.1016/j.apor.2026.105144
• Évaluation de l'influence de la sollicitation par chocs de piles circulaires en site aquatique
  
  • Simon Nicolas
  • Larrarte Frédérique
  • Chevalier Christophe
  • Schmidt Franziska
  • Carmigniani R.
  , 2026. <div><p>L'affouillement, phénomène d'érosion des sols entraînant des creusements, peut impacter les appuis des ponts, les ducs d'Albe, les conditions d'implantation des éoliennes, ... Cela entraine des modifications de conditions aux limites et modifie également les propriétés vibratoires de la structure considérée. Ainsi, une connaissance fine de la relation entre l'affouillement et l'évolution des propriétés vibratoires de la structure pourrait permettre de développer des systèmes d'instrumentations déployables aisément et à bas coût pour la surveillance des structures soumises à cet aléa. Or l'évaluation des modes propres nécessite une sollicitation de la structure. Afin de mieux comprendre ces phénomènes, un modèle réduit de pile circulaire a été réalisé et une fiabilisation de la méthode de sollicitation par chocs est proposée.</p></div>
• Data assimilation of flood maps in a 2D flood model for different performance measures
  
  • Travert Jean-Paul
  • Boyaval Sébastien
  • Goeury Cédric
  • Bacchi Vito
  • Zaoui Fabrice
  Computational Geosciences, Springer Verlag, 2026, 30 (3), pp.45. This study explores the assimilation of uncertain flood maps derived from satellite observations into a 2D hydraulic model to calibrate a spatially varying roughness parameter, which is divided into subdomains. First, a sensitivity analysis is carried out to identify the most influential subdomains for various performance measures. Afterwards, Data Assimilation, specifically the three-dimensional variational method, is used on the reduced subset of parameters to calibrate the roughness field. Different cost function formulations are considered using various performance measures to compare the misfit between observed and simulated flood maps. Using synthetic and real observations, the study evaluates how these measures influence the calibration of model parameters and flood prediction accuracy. The application case is the Garonne River in France, where Synthetic Aperture Radar satellite images were available during flood events. The results indicate that the choice of performance measures in the cost function influences the calibration process. Furthermore, the study highlights that the current precision of derived flood maps is not sufficient for calibrating floodplain roughness. (10.1007/s10596-026-10452-3)
  DOI : 10.1007/s10596-026-10452-3
• Revisiting and enhancing methods of representative wave height selection for medium-term coastal bed level evolution applications
  
  • Papadimitriou Andreas
  • Benoit Michel
  • Karambas Theofanis
  • Tsoukala Vasiliki
  Coastal Engineering, Elsevier, 2026, 211, pp.105071. Accurate prediction of medium-term coastal bed level evolution via numerical modelling is essential for effective coastal management but remains computationally demanding when process-based models are forced with full wave climate datasets. Representative Morphological Wave Height (RMWH) methods offer a practical alternative by reducing wave input while preserving essential morphological principles. This study systematically revisits classical RMWH approaches and proposes three enhanced variants aimed at improving accuracy without increasing computational cost. The examined methods include: (i) the classical RMWH formulation, (ii) an energy-flux-based subdivision of directional bins, (iii) an approach accounting for interchangeable dominance of longshore and cross-shore sediment transport depending on wave incidence angle, and (iv) a variant combining RMWH with an Artificial Neural Network (ANN) to eliminate sea-states unable to initiate sediment motion. All variants were implemented using a coupled process-based numerical model to simulate annual coastal bed evolution at the port of Rethymno, Greece, and benchmarked against a brute-force simulation. Model performance was quantified using the Brier Skill Score (BSS). Results show that the proposed enhancements substantially improve predictive skill compared to the classical RMWH approach, with BSS values increasing from "Good" to "Excellent" while maintaining run-time reductions exceeding 450%. The ANN-assisted RMWH variant exhibited the best overall performance. Further validation against field bathymetric measurements from Eresos beach, Greece, and comparison with two established wave input reduction methods confirmed the robustness and efficiency of the proposed method. The findings underline that enhanced RMWH methods provide an efficient and reliable framework for medium-term coastal bed evolution modelling. (10.1016/j.coastaleng.2026.105071)
  DOI : 10.1016/j.coastaleng.2026.105071
• Evaluating the effects of preprocessing, method selection, and hyperparameter tuning on SAR-based flood mapping and water depth estimation
  
  • Travert Jean-Paul
  • Goeury Cédric
  • Boyaval Sébastien
  • Bacchi Vito
  • Zaoui Fabrice
  Natural Hazards and Earth System Sciences, Copernicus Publ. / European Geosciences Union, 2026. Flood mapping and water depth estimation from Synthetic Aperture Radar (SAR) imagery are crucial for calibrating and validating hydraulic models. This study uses SAR imagery to evaluate various preprocessing (especially speckle noise reduction), flood mapping, and water depth estimation methods. The impact of the choice of method at different steps and its hyperparameters is studied by considering an ensemble of preprocessed images, flood maps, and water depth fields. The evaluation is conducted for two flood events on the Garonne River (France) in 2019 and 2021, using hydrodynamic simulations and in-situ observations as reference data. Results show that the choice of speckle filter alters flood extent estimations with variations of several square kilometers. Furthermore, the selection and tuning of flood mapping methods also affect performance. While supervised methods outperformed unsupervised ones, tuned unsupervised approaches (such as local thresholding or change detection) can achieve comparable results. The compounded uncertainty from preprocessing and flood mapping steps also introduces high variability in the water depth field estimates. This study highlights the importance of considering the entire processing pipeline, encompassing preprocessing, flood mapping, and water depth estimation methods and their associated hyperparameters. Rather than relying on a single configuration, adopting an ensemble approach and accounting for methodological uncertainty should be privileged. For flood mapping, the method choice has the most influence. For water depth estimation, the most influential processing step was the flood map input resulting from the flood mapping step and the hyperparameters of the methods. (10.5194/nhess-26-2387-2026)
  DOI : 10.5194/nhess-26-2387-2026
• Évaluation et fiabilisation de méthodes de sollicitations de modèle réduit de structure application à la détection d'affouillement autour de pile de pont
  
  • Simon Nicolas
  • Larrarte Frédérique
  • Chevalier Christophe
  • Schmidt Franziska
  , 2026. Les propriétés vibratoires d'une structure dépendent notamment des conditions aux limites. L'affouillement, phénomène d'érosion des sols se produisant notamment aux pieds des piles de ponts en site aquatique, se traduit par une modification de ces conditions en induisant un décalage des fréquences propres. Pour étudier ce phénomène, un modèle réduit en laboratoire a été réalisé. L'étude des propriétés vibratoires d'une structure nécessite l'excitation de celle-ci. Dans cette étude, des méthodes de sollicitation par bruit ambiant, shaker et chocs ont été utilisées sur un modèle réduit de pile de pont instrumenté par un accéléromètre triaxial. Un des enjeux repose sur la fiabilisation de la sollicitation et donc du marteau. Un état de l'art portant sur les méthodes de sollicitations puis une évaluation de ces méthodes appliquées à un modèle réduit de pile de pont est mis en place. Finalement, une fiabilisation de la méthode de sollicitation par impact est réalisée.
• Physics of propulsion in front crawl swimming
  
  • Brunel Thomas
  , 2026. This thesis investigates the physics of propulsion in front crawl, with particular emphasis on the respective contributions of the arms and legs as a function of swimming speed. While the dominant role of the arms is well established, the contribution of the legs and the mechanisms governing propulsion at different intensities remain incompletely understood.Chapter 1 introduces the research problem by presenting the physical framework adopted and relating it to the existing literature. It also provides a review of available methods for measuring propulsive forces in swimming, leading to the selection of instrumented hand paddles, which are used throughout this work.Chapter 2 describes the experimental setup and data analysis methods. The experiments are based on an incremental speed test consisting of repeated pool lengths performed at increasing intensity. Different swimming conditions are defined to isolate the respective contributions of the arms and legs. Forces exerted at the hands are measured using the instrumented paddles, while swimming speed is estimated using a multi-camera system.Chapter 3 examines the relationship between swimming velocity and stroke frequency across the different tests. The results show that the instrumented paddles negatively affect swimming performance; however, this effect remains moderate, thereby validating their use for characterizing propulsive forces in front crawl. The findings also reveal an increase in the propulsive contribution of the legs with intensity, rising from negligible at low speeds to significant at maximal intensity.Chapter 4 provides a dynamical interpretation of this evolution, showing that leg-induced propulsion increases more rapidly with movement frequency than arm-generated propulsion. Force measurements at the hands indicate that arm propulsion increases linearly with stroke frequency, whereas the speed-frequency relationship observed during leg-only tests suggests that leg propulsion increases with the square of the frequency. This difference explains the increasing importance of the legs at higher speeds. This effect is further reinforced by an energy optimization strategy: at low intensity, swimmers tend to engage their legs less actively, as leg propulsion is metabolically more costly than arm propulsion.Finally, Chapter 5 investigates the mechanisms underlying force production at the hands. Two main contributions are identified: one related to hand velocity, and thus to hydrodynamic drag, and the other associated with the acceleration of the surrounding water mass. Swimmers tend to rely on one or the other mechanism, and in some cases each arm may preferentially use a different strategy. Given the homogeneity of the tested group, this suggests that both mechanisms are compatible with high-level performance.Overall, this work provides a physical framework for understanding propulsion in front crawl and opens new perspectives for performance optimization and the development of novel measurement methods in swimming.
• Impact of Bed Roughness and Submergence on Velocity Profiles and Flow Structures in Hydraulic Jumps
  
  • Agrawal Nishank
  • Padhi Ellora
  • Larrarte Frédérique
  • Singhal Gopal Das
  Scientific Reports, Nature Publishing Group, 2026, 16 (1), pp.11676. Hydraulic jumps downstream of spillways exhibit high near-bed velocities that can induce cavitation and scour. While bed roughness is known to modify velocity distribution and roller characteristics, the underlying flow physics governing velocity transition, turbulence dissipation, and vortex evolution under varying submergence conditions remain insufficiently understood.<p>This study presents an integrated experimental and numerical investigation of free and submerged hydraulic jumps over smooth and corrugated beds to elucidate these mechanisms. Experiments were conducted at discharges of 11, 13, and 15 l s⁻ ¹ for submergence ratios ranging from 0 to 0.4, and complemented by three-dimensional CFD simulations using a RANS-based RNG k-ε model in FLOW-3D. Detailed analyses of velocity similarity profiles, boundary layer development, turbulent kinetic energy (TKE), dissipation rate, total energy loss, and Q-criterion based vortex structures were performed. The results reveal that bed corrugation accelerates boundary layer development, enhances turbulence breakdown, and increases energy dissipation compared to smooth beds. Submergence shifts the turbulence generation zone downstream and increases roller length; however, corrugated beds consistently confine coherent vortices and reduce near-bed velocity under all tested conditions. The study provides new physical insight into turbulence-roughness-submergence interactions in spillway-induced hydraulic jumps and offers design guidance for improving stilling basin performance and reducing downstream scour risk. (10.1038/s41598-026-44480-x)
  DOI : 10.1038/s41598-026-44480-x
• 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
• A Unified Two-Dimensional Framework for Modeling Bedload and Suspended Sediment Transport and Morphodynamics in Rivers
  
  • Lupinski Kim-Jehanne
  , 2026. Predicting morphological changes in rivers constitutes a critical challenge for engineering and environmental management, particularly in regulated systems. Traditional numerical models typically partition sediment transport into bedload and suspended load. This artificial dichotomy relies on empirical thresholds that often fail to accurately capture transitional regimes where both modes coexist. This thesis introduces an Extended Unified Sediment Transport Model (EUSTM) designed to simulate the transport of non-cohesive sediments as a continuous process within a two-dimensional framework. Implemented in the open-source system openTELEMAC, the model relies on a transport-length formulation governed by the characteristic height and velocity of the sediment layer, bridging the gap between near-bed motion and suspension. The model performance is first evaluated against a comprehensive dataset of flume experiments under equilibrium conditions. Refining the parameterization of the saltation height significantly enhances accuracy, enabling the unified model to achieve performance comparable to classical dual-mode approaches, while avoiding the need to select between bedload and suspension. In a second phase, the framework is applied to large-scale morphodynamic instabilities, specifically the formation of alternate bars. Numerical simulations successfully capture the transition from bedload-dominated to suspension-influenced patterns, reproducing observed variations in bar geometry without explicit regime switching. By offering a physically consistent and continuous description of sediment dynamics, this unified framework provides an interesting alternative for modeling complex fluvial environments.
• 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
• 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
• 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
• 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
• 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
• Mesure de l'érosion des sables : quand le numérique et l'expérimental se complètent pour developper un erodimètre
  
  • Nicolas Xavier
  • Larrarte Frédérique
  • Merzoud Massinissa
  • Michard Clément
  • Chevalier Christophe
  LHB Hydroscience Journal, Taylor & Francis Group, 2026, 112 (1), pp.2673991. Un prototype d'érodimètre de terrain, léger et « low cost », a été développé. Nommé PumpET pour Pump Erosion Test, il est dédié à la mesure de l'érodabilité de sédiments fins déposés dans le lit des rivières. Le principe de cet appareil consiste à imposer, à l'aide d'une pompe, des paliers croissants et contrôlés de débits d'eau dans la chambre de mesure, de forme convergente, mise en contact avec le lit de la rivière. La localisation des seuils d'arrachement particulaire est détectée par traitement d'image de vidéos qui filment la chambre. En parallèle, des simulations numériques des écoulements dans la chambre permettent de remonter à la contrainte de cisaillement imposée au niveau du seuil d'arrachement. Nous présentons la démarche expérimentale qui a permis le développement PumpET. Nous détaillons ensuite l'étude numérique RANS-RSM des écoulements dans la rivière et dans le PumpET. Ces simulations montrent que le PumpET génère un champ de contrainte de cisaillement adéquat dans toute la chambre de mesure, pour une large gamme de rapports d'amplitude et de déviation angulaires entre les vitesses d'écoulements dans la rivière et dans la chambre. Cette étude permet aussi de dégager des perspectives d'amélioration du PumpET. (10.1080/27678490.2026.2673991)
  DOI : 10.1080/27678490.2026.2673991