Publications

2025

• Caractérisation expérimentale et modélisation de la dispersion atmosphérique en vent faible et en milieu bâti
  
  • Bounouas Hanane
  , 2025. La dispersion atmosphérique en conditions de vent faible est souvent mal prise en compte voire négligée dans les études d’impact. Dans de telles conditions, les mécanismes de dispersion subissent des modifications importantes, les propriétés de la turbulence (spectre, anisotropie) sont sensiblement différentes, et le méandrement, caractérisé par des oscillations de basse fréquence à l’échelle sub-meso de la direction du vent, devient souvent prédominant, entraînant une forte variation de la concentration sur une large plage angulaire autour de la source. Le développement de modèles prenant en compte ces processus est d’autant plus difficile que l’on constate un manque de données expérimentales pour ce type de situations, notamment en milieu bâti.La thèse inclut un volet expérimental et un volet modélisation. La partie expérimentale réalisée au SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique, installé sur le campus de l’école Polytechnique à Palaiseau en milieu péri-urbain) comporte deux parties. La première est dédiée à l’analyse statistique de mesures haute fréquence des composantes du vent sur une période de trois ans pour étudier les propriétés du méandrement et son interaction avec la turbulence. La seconde consiste en la réalisation et l’analyse de campagnes de mesures pour acquérir des données expérimentales de dispersion d’un gaz traceur (Hélium) en milieu bâti et en conditions de vent faible. La partie modélisation porte sur la définition et la validation d’une méthodologie de modélisation CFD avec le code open source code_saturne adaptée à ces situations, en s’appuyant sur les cas documentés pendant les campagnes expérimentales, notamment ceux présentant du méandrement. Trois approches de type RANS (Reynolds Averaged Navier Stokes) ou URANS (Unsteady Reynolds Averaged Navier Stokes) sont étudiées :- une simulation en régime stationnaire intégrant des conditions aux limites constantes ;- une simulation pseudo-instationnaire impliquant une combinaison de cas stationnaires, réalisée avec différentes conditions d'entrée représentatives de la variation temporelle des conditions météorologiques pendant le rejet ;- une simulation en régime instationnaire avec des conditions aux limites variables. Dans le but de valider les différentes approches, des comparaisons entre les résultats de modélisation obtenus et les mesures ont été réalisées, tant pour les variables dynamiques que pour la concentration du traceur. (10.70675/fb16815bz2a77z4b2cz9b82zcd30fac962c4)
  DOI : 10.70675/fb16815bz2a77z4b2cz9b82zcd30fac962c4
• Development of an offline and online hybrid model for the Integrated Forecasting System
  
  • Farchi Alban
  • Chrust Marcin
  • Bocquet Marc
  • Bonavita Massimo
  Quarterly Journal of the Royal Meteorological Society, Wiley, 2025, 151 (768). In recent years, there has been significant progress in the development of fully data‐driven global numerical weather prediction models. These machine learning weather prediction models have their strengths, notably accuracy and low computational requirements, but also their weaknesses: they struggle to represent fundamental dynamical balances, and they are far from being suitable for data assimilation experiments. Hybrid modelling emerges as a promising approach to address these limitations. Hybrid models integrate a physics‐based core component with a statistical component, typically a neural network, to enhance prediction capabilities. In this article, we propose to develop a model‐error correction for the operational Integrated Forecasting System (IFS) of the European Centre for Medium‐Range Weather Forecasts using a neural network. The neural network is initially pre‐trained offline using a large dataset of operational analyses and analysis increments. Subsequently, the trained network is integrated into the IFS within the Object‐Oriented Prediction System (OOPS) so as to be used in data assimilation and forecast experiments. It is then trained further online using a recently developed variant of weak‐constraint 4D‐Var. The results show that the pre‐trained neural network already provides a reliable model‐error correction, which translates into reduced forecast errors in many conditions, and that the online training improves the accuracy of the hybrid model further in many conditions. (10.1002/qj.4934)
  DOI : 10.1002/qj.4934
• A coupled approach to compute approximate solutions of a compressible immiscible three-phase flow model with fast transient and stiff source terms
  
  • Hérard Jean-Marc
  • Jomée Guillaume
  SMAI Journal of Computational Mathematics, Société de Mathématiques Appliquées et Industrielles (SMAI), 2025, 11, pp.405-434. This paper aims at developing a new numerical coupled approach to compute solutions of a compressible immiscible three-phase flow model with stiff source terms. The targeted applications involve flows with fast transient and shock waves. Thus, a well-posed model with respect to the initial conditions that embarks an entropy inequality is considered. A preliminary work on the underlying relaxation process of the model is conducted. Then the new numerical scheme is presented and numerically tested. (10.5802/smai-jcm.129)
  DOI : 10.5802/smai-jcm.129
• Numerical analysis of evaporation reduction in floating photovoltaic power plants: influence of design parameters
  
  • Berlioux Baptiste
  • Amiot Baptiste
  • Ferrand Martin
  • Le Berre Rémi
  • Rhazi Oume-Lgheit
  • Vidal Javier
  • Pabiou Hervé
  • Knikker Ronnie
  EPJ Photovoltaics, EDP sciences, 2025, 16, pp.4. Evaporation reduction is one of the advantages provided by floating photovoltaic (FPV) power plants. However, few studies have yet been carried out to understand how to optimise the layout of FPV power plants in order to provide better water management. Indeed, the interaction between atmospheric conditions, water bodies, and the FPV plant creates a dynamic system that is challenging to study and accurately model. This paper investigates the impact on evaporation of various characteristics of FPV plants, such as float technology, plant positioning and orientation, distribution, and coverage ratio. This study was performed using Computational Fluid Dynamics (CFD) of the surrounding atmosphere, with the impact of the FPV plant modelled using specific boundary conditions to reduce computational costs. The numerical results show that the coverage ratio is the most important factor in reducing evaporation. Full coverage could reduce evaporation by 52.8% for a plant with a large footprint on the water and by 43.4% for a plant with a smaller footprint. Other parameters have only a moderate impact, allowing the fine-tuning of evaporation reduction. The optimal configuration would involve covering the entire water body with a single large water footprint island positioned downwind of the prevailing transversal winds. This setup significantly reduces evaporation, thereby enhancing water conservation and making an FPV power plant a valuable tool in sustainable water management. (10.1051/epjpv/2024047)
  DOI : 10.1051/epjpv/2024047
• A Godunov-type scheme and a relaxation scheme for second-order turbulence-moment models
  
  • Bennoura-Bouchiba Nadjib
  • Ferrand Martin
  • Hérard Jean-Marc
  ESAIM: Mathematical Modelling and Numerical Analysis, Société de Mathématiques Appliquées et Industrielles (SMAI) / EDP, 2025, 59 (5). A Godunov-type scheme and a relaxation scheme are presented to approximate discrete solutions of the convective subsystem arising from a second-order turbulence model in the incompressible framework. An analytical representation is proposed for the case of the occurrence of a laminar zone. Numerical tests of the two schemes and a comparison with the Rusanov scheme complete the paper. (10.1051/m2an/2025066)
  DOI : 10.1051/m2an/2025066
• Two unsteady solutions of a homogeneous equilibrium model in a porous medium
  
  • Hérard Jean-Marc
  • Lazare Gauthier
  ESAIM: Proceedings and Surveys, EDP Sciences, 2025, 78, pp.136-143. We present in this note two reference one-dimensional unsteady solutions of a HEM model, considering possible heat source terms, and focusing on a steady porous medium. The model is recalled first, then details on exact solutions are provided. Several Equations Of State are discussed. (10.1051/proc/202578136)
  DOI : 10.1051/proc/202578136
• Harmonised boundary layer wind profile dataset from six ground-based Doppler wind lidars in a transect across Paris, France
  
  • Morrison William
  • Looschelders Dana
  • Céspedes Jonnathan
  • Claxton Bernie
  • Drouin Marc-Antoine
  • Dupont Jean-Charles
  • Faucheux Aurélien
  • Holst Christopher C
  • Kotthaus Simone
  • Masson Valéry
  • Mcgregor James
  • Price Jeremy
  • Zeeman Matthias
  • Grimmond Sue
  • Christen Andreas
  Earth System Science Data, Copernicus Publications, 2025, 17 (11), pp.6507-6529. Doppler wind lidars (DWL) offer high-resolution wind profile measurements that are valuable for understanding atmospheric boundary layer (ABL) dynamics. Here six ground-based DWL, deployed in a multi-institutional effort along a 40 km transect through the centre of Paris (France), are used to retrieve horizontal wind speed and direction through the ABL at 18–25 m vertical and 1–60 min temporal resolution. Data are available for June 2022–March 2024 (three DWL) and two Intensive Observation Periods (six DWL) across 9 weeks in September 2023–December 2023. Data from all sensors are harmonised in terms of quality control, file format, as well as temporal and vertical resolutions. The quality of this DWL dataset is evaluated against in-situ measurements at the Eiffel Tower and radiosonde profiles. This unique, spatially dense, open dataset will allow urban boundary layer dynamics to be explored in process-studies, and is further valuable for the evaluation of high-resolution weather, climate, inverse and air pollution models that resolve city-scale processes. The dataset is available at https://doi.org/10.5281/zenodo.14761503 (Morrison et al., 2025). (10.5194/essd-17-6507-2025)
  DOI : 10.5194/essd-17-6507-2025