Martin Oberlack is Professor of Mechanical Engineering at Darmstadt University and holder of the chair for fluid dynamics. He received his Bachelors degree in Mechanical Engineering from the University of Essen in 1985. His Diploma degree he obtained in 1988, his Ph.D. degrees in 1994 and his Habilitation in 2000 all from the RWTH Aachen. He joined the TU Darmstadt faculty of Civil Engineering in September 2000. After various external offers, which he declined, he changed to the Department of Theoretical and Applied Mechanics in 2005 and one year later he switched to the Department of Mechanical Engineering. He co-founded the Center of Smart Interfaces and the Graduate School of Excellence Computational Engineering at Darmstadt University. He has been actively involved in the editorial boards of the Theor. & Comp. Fluid Dynamics, Continuum Mech. & Thermodyn. and Fluid Dynamic Research, for which he is an editor, and he recently joint the editorial board of Communications Physics / Nature. He is presently co-editor of two book Series “Mathematical Physics: Theory and Applications” and “Progress in Turbulence - Fundamentals and Applications” Springer publisher. His refereeing activities include almost fifty international journals and nearly thirty national and international funding organizations.
Prof. Oberlack pioneered the use of Lie symmetry methods for the study of turbulence physics and statistics, combustion and modelling concepts and has written widely on this with a special focus on turbulent shear flows. His current interests include: Lie symmetries of the Lundgren-PDF and Hopf equation of turbulence, construction of conservation laws, hydrodynamic stability theory, Fokas unifying method for multi-phase problems, aerodynamic noise, combustion, high-performance and parallel computing, GPU acceleration, Discontinuous Galerkin numerical methods with special focus on singular problems such as multi-phase flows and large-scale direct turbulence simulations.
Already for this Habilitation thesis in 2000, in which he laid the foundation for the symmetry-based turbulence theory, he was awarded the Friedrich-Wilhelm Award of RWTH Aachen and the Academy Award of the North Rhine-Westphalia Academy of Sciences and he received the Hermann-Reissner-Award of the Dept. of Aero- and Astronautics of the University of Stuttgart for his Contributions in Turbulence Research. In 2013 he was awarded both the Athene Best Teaching Award of the Department of Mechanical Engineering and the E-Teaching-Award of TU Darmstadt for the innovative development of electronic media in teaching. He is an elected a Fellow of the American Physical Society for his pioneering use of symmetry methods for the study of turbulence and related fields and the derivation of new conservation laws in fluid dynamics.
Prof. Oberlack is a member of the American Physical Society, the German Committee for Mechanics, the International Association of Applied Mathematics and Mechanics, the European Mechanics Society, the European Research Community on Flow, Turbulence and Combustion and the Society for Industrial and Applied Mathematics.
Turbulent scaling laws of high moments in wall-bounded shear flows
Abstract: Using the symmetry-based turbulence theory, we derive turbulent scaling laws in wall-bounded shear flows for arbitrarily high moments of the flow velocity U1. The key ingredients are the symmetries of classical mechanics, especially the scaling of space and time, and two statistical symmetries, which are not directly observed in Euler and Navier-Stokes equations. These symmetries are admitted by all complete theories of turbulence, i.e. the infinite hierarchy of moment and PDF equations and also by the famous Hopf functional equation. The symmetries provide a measure of intermittency and non-Gaussian behavior – properties that have been investigated for decades for turbulence and are now subject to a rigorous description. Based on the above, in the near-wall region the symmetry theory predicts a log-law for the mean velocity (n=1) and an algebraic law with the exponent w (n – 1) for moments n > 1. Hence, the exponent w of the 2nd moment determines the exponent of all higher moments. Most important, moments here always refer to the instantaneous velocities U and not to the fluctuations u’. For the core regions of both plane and round Poiseuille flows we find a deficit law for arbitrary moments n of algebraic type with a scaling exponent n (s2 – s1) + 2 s1 – s2. Hence, the moments of order one and two with its scaling exponents s 1 and s 2 determine all higher exponents. Those parts of the exponents that do not scale with n indicate anomalous scaling and have their origin in the intermittency symmetry. All theoretical results are validated very well by a new plane Poiseuille flow DNS at Ret = 104 and by pipe flow data from the CICLoPE (Uni Bologna) and Superpipe (Princeton) flow experiments. Recent extensions to invariant solutions of the PDF are also presented.
19 mai 2022, 16h3017h30
Please contact J.-P Laval or F. Romano for the link
