Viabilité et performance des solveurs points de grille dans la résolution du problème implicite du noyau dynamique du modèle AROME

AROME est le modèle a aire limitée de Prevision Numerique du Temps (PNT) de Meteo- France. Son noyau dynamique resout les equations d’Euler pleinement compressibles non- hydrostatiques a une résolution horizontale kilométrique. Pour respecter les delais fortement contraints inherents a la PNT, les methodes numeriques utilisent le mieux possible des supercalculateurs composes d’un grand nombre de nœuds travaillant en parallèle. Le noyau dynamique semi-implicite aujourd’hui utilise, est base sur un opérateur linéaire a coefficients constants qui traite implicitement les termes responsables de la propagation des ondes les plus rapides, contournant ainsi les contraintes de stabilité numérique les plus fortes et autorisant de grands pas de temps intégration. Cet opérateur autorise également l’utilisation d’une discrétisation spectrale des opérateurs de dérivée horizontale a l’aide d’un algorithme de transformée de Fourier rapide, peu scalable sur les machines parallèles du futur. De plus, en traitant les termes orographiques explicitement, donc soumis a des contraintes de stabilité, les resolutions hectometriques du futur représentant notamment mieux les plus fortes pentes des reliefs, ne peuvent être abordées avec ces schémas. Dans cette thèse, nous abandonnons les schémas a coefficients constants d’une part et la discrétisation spectrale d’autre part, pour améliorer la stabilité numérique au voisinage des plus fortes pentes pour les futures architectures de calcul

Refinement of a mesoscale model for large eddy simulation

With the advent of wind energy technology, several methods have become mature and are seen today as standard for predicting and forecasting the wind. However, their results are still site dependent, and the increasing sizes of both modern wind turbines and wind farms tackle limits of existing methods. Some triggered processes extend to the junction between microscales and mesoscales.The main objectives of this thesis are thus to identify, implement and evaluate an approach allowing for microscale and mesoscale ABL flow modelling considering the various challenges of modern wind energy applications. A literature review of ABL flow modelling from microscales to mesoscales first provides an overview of the specificities and abilities of existing methods. The combined mesoscale/large eddy simulation (LES) modelling appears to be the most promising approach, and the Compressible Community Mesoscale Model (MC2) is elected as the basis of the method in which the components required for LES are added and implemented. A detailed description of the mathematical model and the numerical aspects of the various components of the LES-capable MC2 are then presented so that a complete view of the proposed approach along with the specificities of its implementation are provided. This further allows to introduce the enhancements and new components of the method (separation of volumetric and deviatoric Reynolds tensor terms, vertical staggering, subgrid scale models, 3D turbulent diffusion, 3D turbulent kinetic energy equation), as well as the adaptation of its operating mode to allow for LES (initialization, large scale geostrophic forcing, surface and lateral boundaries). Finally, fundamental aspects and new components of the proposed approach are evaluated based on theoretical 1D Ekman boundary layer and 3D unsteady shear and buoyancy driven homogeneous surface full ABL cases. The model behaviour at high resolution as well as the components required for LES in MC2 are all finely evaluated, including: the dynamic kernel at high resolution; space and time discretization of the 3D turbulent diffusion; five subgrid scale models; and the sensitivity of the model to numerical parameters. Furthermore, LES test cases are thoroughly studied, showing that a longer time interval for post-processing than in the reference studies is needed due to a high but normal level of scatter in the results. In the end, the obtained LES-capable mesoscale model is shown to perform on par with other similar reference LES models, albeit it is slightly more dissipative. It is thus demonstrated that the adapted MC2 is suitable for both micro- and mesoscales providing a strong foundation for more advanced studies

Novel Antibacterial Agents

This book was devoted to the latest advances achieved in the antibacterial field, with a focus on the recent efforts made to develop new antimicrobial agents with novel modes of action, and a perspective on future directions of this line of research. Antimicrobial resistance has become a major threat to global health, and the twenty-two published articles here reported put in evidence that the discovery and development of new antibiotics are extremely challenging. The antimicrobial research covers a wide area, spanning from the design of new compounds, also supported by molecular modeling techniques, their synthesis and characterization, and biological tests.In this context, the current crisis caused by the COVID-19 pandemic, but also older threats, such as the human immunodeficiency virus or the hepatitis C virus, require greater attention than ever.The research works described in this book provide an extremely useful example of the results achieved in the field of antibacterial drug development. The search for new chemical entities was approached starting from both natural and synthetic compounds and addressing different targets. In addition, recent findings were presented and discussed highlighting the strategies to fight bacterial resistance. Detailed references to the state-of-the-art can be found in this book.We strongly encourage the wide group of readers to explore the book that we are presenting, to get inspired to develop new approaches for the diagnosis and treatment of antibacterial diseases, and to circumvent resistance issues

EBook proceedings of the ESERA 2011 conference : science learning and citizenship

This ebook contains fourteen parts according to the strands of the ESERA 2011 conference. Each part is co-edited by one or two persons, most of them were strand chairs. All papers in this ebook correspond to accepted communications during the ESERA conference that were reviewed by two referees. Moreover the co-editors carried out a global reviewing of the papers.ESERA - European Science Education Research Associatio