04 novembre 2021

Wébinaire J. Christos Vassilicos

J. Christos Vassilicos was Reader in Fluid Mechanics at Imperial College London till 2003 then Professor of Fluid Mechanics till 2019 in the Department of Aeronautics. Since 2019, he is "Directeur de Recherche" CNRS at LMFL, France and Visiting Professor in the Departments of Mathematics and of Aeronautics of Imperial College London. He was awarded of an European Research Council Advanced Grants (ERC) from 2013 to 2018 and Principal Investigator of the Marie Curie Innovative Doctoral Porgramme MULTISOLVE. He co-authored more than 150 international refereed journal papers and supervised 34 PhD students and 14 post-docs.
Scalings of scale-by-scale turbulence energy in non-homogeneous turbulence

Abstract: Quoting Kraichnan, the 2/3 and -5/3 power laws of Kolmogorov and Obukhov have « achieved an embarassment of success » as they have « been found not only where they reasonably could be expected » but also where the Kolmogorov theory is not designed for, e.g. in significantly non-homogeneous and near-field turbulence. The Kolmogorov theory of the turbulence cascade and scale-by-scale energy must therefore be a special case of a more general turbulence theory. To break beyond the Kolmogorov theory we need to break beyond its most constraining assumptions: equilibrium and homogeneity. Some progress has been made on non-equilibrium cascades and dissipation over the past ten years and so this talk’s focus is on non-homogeneity. A theory of non-homogeneous turbulence is developed and is applied to boundary-free shear flows. The theory introduces assumptions of inner and outer similarity for the non-homogeneity of two-point statistics and predicts power law scalings of second-order structure functions which have some similarities with but also some differences from Kolmogorov scalings. These scalings arise as a consequence of these assumptions, of the general inter-scale and inter-space energy balance and of an inner-outer equivalence hypothesis for turbulence dissipation. They reduce to usual Kolmogorov scalings in stationary homogeneous turbulence. Comparisons with structure function data from three qualitatively different turbulent wakes provide support for the theory’s predictions but also raise many new questions for future research.

04 novembre 2021, 16h3017h30
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01 décembre 2022

Wébinaire Esteban Ferrer

New avenues in high order fluid dynamics

Esteban Ferrer est professeur de mathématiques appliquées à l'école d'aéronautique (ETSIAE-UPM). Il a obtenu son doctorat à l'université d'Oxford (Royaume-Uni) et possède 20 ans d'expérience industrielle et universitaire dans le développement de techniques numériques pour les problèmes de fluides. Il travaille activement avec l'industrie et coordonne deux projets Européens. Ses principaux intérêts sont les méthodes d'ordre élevé pour la dynamique des fluides, la modélisation de la turbulence, l'apprentissage automatique, l'aéroacoustique pour l'aéronautique et l'énergie éolienne. Il a rédigé plus de 90 articles de journaux et de conférences sur ces sujets.