Date : on October 31st, from 9:00 AM to 12:00 PM ; amphi N°3 - Centrale Méditerranée

Abstract : Wind energy experienced fast growth in the past two decades due to its inherent cleanness and low economic cost. Much attention has been devoted to the wind turbine/farm to access the full potential of wind energy. Wind turbines extract energy from airflow, resulting in a high turbulence and low-velocity wake flow. The downstream wind turbines in the wake suffer from high load and reduce power production. Additionally, wind turbine aerodynamics are highly influenced by the characteristics of the atmospheric boundary layer (ABL). Therefore, a thorough study of the interaction between wind farms and ABL is crucial for the design of wind farms and the optimization of wind farm performance.

Numerical simulations offer advantages in quantitative analysis of interactions between wind farms and ABL compared to experimental studies. While conventional high-fidelity simulations provide valuable insight into wind farm aerodynamics, their high computational cost limits their industrial application. As an alternative, the efficient lattice Boltzmann method (LBM) offers a promising solution for balancing computational demands whilst enabling accurate aerodynamic analysis. In this study, LBM was integrated with Large Eddy Simulation (LES) to investigate the wake flow of wind turbines and wind farms. The wind turbines were parameterized using the actuator line model. The ground momentum and the thermal flux within the ABL are represented using the Monin-Obukhov similarity theory. A review of different inflow turbulence generation methods in wind energy was provided. The inflow turbulence was constructed using the synthetic eddy method (SEM) as an alternative to the widely used precursor method.

A comprehensive validation of the numerical model was first carried out, including the integration of the wind turbine actuator line model into the LBM-LES solver, the simulation of individual wind turbine wake flow under the influence of atmosphere stability, and the wind farm simulation under neutral boundary layer (NBL) conditions. The results showed good agreement with reference data. The individual wake flow characteristics, such as velocity deficit shape and wake flow recovery rate, are highly influenced by thermal stability. The wake flow inside a wind farm stabilizes after an initial adjustment in the uniform temperature condition.

Onshore and offshore wind farm wakes under the influence of ABL thermal stability were further studied. For the onshore wind farm, the effects of stable and convective conditions were analyzed in detail. The wake behind the first 2 rows of the wind farm recovers faster in the convective condition due to the high ambient turbulence. However, the velocity and the turbulence intensity of the stabilized wake are higher in the stable condition. This is attributed to the larger velocity gradient and increased shear stress in the stable environment, which enhances the vertical kinetic energy exchange. The thermal stability effect can be differentiated between the indirect and direct effects. Indirectly, thermal stability influences ambient turbulence magnitude and velocity gradient, leading to varying levels of turbulence production and energy exchange. Directly, buoyancy forces primarily impact the wake flow behind the first two rows of turbines. Beyond this point, turbine rotation mixes high and low-temperature flows, rendering the flow relatively neutral deeper inside the wind farm. In addition, the performance of two typical analytical models was analyzed by comparison with the current LES results. The results highlight the importance of considering turbulence intensity in analytical models. Current empirical models for wind turbine-induced turbulence do not adequately represent variations induced by thermal stability.

As for the offshore wind farm, simulations were conducted with constant sea surface roughness. The wake flow stabilizes after the second wind turbine, with a slower wake recovery due to the lower inflow turbulence intensity compared to the onshore wind farm. A comparison was further performed between the results of the analytical models and the LES. The PARK model overpredicts the wake flow velocity behind the first turbine while underpredicting the near wake velocity and overpredicting the far wake velocity from the second turbine onwards. This is attributed to the low wake recovery rate predictions. The NPA model underpredicts wake flow behind the first turbine but performs well in predicting the wake flow at equilibrium, with overprediction in front of each row of turbines due to the model not accounting for the blockage effect.

These findings offer valuable insights into the aerodynamic and thermal dynamics within large wind farms, both onshore and offshore, contributing to the optimization of wind energy production.

Michel VISONNEAU    - Rapporteur              Directeur de recherche            CNRS

Guillaume BALARAC   - Rapporteur              Professeur des universités      Université de Grenoble

Sylvain GUILLOU        - Examinateur            Professeur des universités      Université de Caen

Mickael GRONDEAU  - Examinateur            Maître de conférences             Université de Caen

Frédéric BLONDEL     - Examinateur            Ingénieur de recherche            IFPEN

Sandrine AUBRUN      - Présidente du Jury  Professeure                              Ecole Centrale de Nantes

Pierre SAGAUT           - Directeur de thèse  Professeur des universités        Aix-Marseille Université

Jérôme JACOB           - Membre invité         Ingénieur de recherche             CNRS 

Date : le 24 septembre à 9h00, amphithéâtre du CEREGE, technopole de l'Arbois

Abstract : Age-related macular degeneration (AMD), manifested by the appearance of a dark spot in the center of the vision, has become a significant public health issue, with the number of patients set to rise over the coming decades. Since 2006, the pharmaceutical industry has introduced therapies with monthly intravitreal injections of anti-VEGF (vascular endothelial growth factor) antibodies to mitigate its development. Designing an intravitreal implant with antibody release controlled over twelve weeks has been proposed to simplify therapy management. Antibodies are thermally, chemically, and biologically sensitive therapeutic proteins. This study demonstrates the potential of the Sequential Dispersion Particles from Gas Saturated Solution (SD-PGSS) process for encapsulating sensitive active ingredients. The SD-PGSS process enables work to be carried out at moderate temperatures (38 °C) and without solvent. The study focused on the optimization of operating conditions through the investigation of polyesters (Polycaprolactone PCL, poly(Lactide-co-Glycolide) PLGA, and a polyether (Poly(Ethylene Glycol) PEG) biocompatible in the presence of supercritical CO2. Two operating conditions were selected: 38 °C/25 MPa for PCL and the PCL/PLGA blend (1:1 w/w) and 45 °C/25 MPa for PCL alone and the PCL/PEG blend (1:1 w/w). The implementation of the SD-PGSS process resulted in a repeatable process with high yields (80 - 95%). The study of two model molecules, lutein, a small hydrophobic molecule of therapeutic interest studied in an oral administration context, and bovine serum albumin, a hydrophilic protein studied in an intravitreal release scenario, demonstrated the repeatability of the process, the homogeneity of the final product, and the possibility of modulating the release in vitro. The antibody study demonstrated low activity maintenance and prolonged release for up to 8 weeks, leading to a prototype with compatible dimensions for ophthalmic use.

Géraldine PIEL                         Rapporteuse / Professeure, Université de Liège, Belgique

Ernesto DI MAIO                      Rapporteur / Professeur, Université de Naples-Federico II, Italie

Martial SAUCEAU                    Examinateur / Maître-assistant, Ecole des Mines d’Albi-Carmaux

John CONRATH                       Président du jury / Professeur - Chirurgien, Clinique Monticelli 

Elisabeth BADENS                   Directrice de thèse / Professeure, Aix-Marseille Université 

Yasmine MASMOUDI               Co-directrice de thèse / Maître de conférences , Aix-Marseille Université

Frédéric MATONTI                   Membre invité / Professeur - Chirurgien , Clinique Monticelli

Céline OLMIERE                      Membre invitée / Directrice scientifique, Théa Open Innovation 

Résumé : La mise en œuvre des procédés membranaires pour le traitement des eaux et des effluents a connu un essor considérable ces dernières années grâce à leur potentiel d’intensification des filières industrielles. Par rapport aux procédés conventionnels de séparation, les procédés membranaires permettent généralement une augmentation de la productivité et de la sélectivité, une réduction de l’emprise au sol, une réduction de la consommation en produits chimiques, et même souvent une réduction des coûts d’investissement et de fonctionnement. Ils permettent aussi des séparations sur une large gamme de tailles, du micromètre au nanomètre. Dans ce contexte d’intensification et en considérant les enjeux actuels majeurs de la protection de l’environnement et de la ressource en eau, il s’agit d’étudier l’efficacité des procédés membranaires dans les domaines de la production d’eau potable, de la production d’eau pour des applications industrielles, du traitement des eaux usées domestiques et des effluents industriels. Les travaux présentés dans ce manuscrit d’Habilitation à Diriger les Recherches visent donc à améliorer l'efficacité et la durabilité des filières de traitement des eaux et des effluents, en se concentrant sur la réduction de l'impact environnemental pour diverses applications et sur l'amélioration de la qualité de l’eau en particulier vis-à-vis de polluants microbiologiques et microplastiques. Dans ce cadre, les résultats obtenus ont ainsi contribué à améliorer l’état des connaissances scientifiques au sujet de la faisabilité des procédés membranaires pour de nouvelles applications et de l’optimisation de leur fonctionnement à échelle semi-industrielle voire industrielle. Le développement de techniques analytiques poussées au service du Génie des Procédés est un réel apport à cette intensification. Des perspectives de recherche pour une utilisation plus sûre et plus durable de l’eau grâce aux procédés membranaires sont également présentées.

Mots-clés : procédés membranaires, intensification, génie des procédés, traitement de l'eau, eau potable, eaux usées, effluent industriel, polluants émergents