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Joint Chinese-Russian Mathematical Online Colloquium

11:00 (GMT+3)
Jin-Han Xie Jin-Han Xie
Peking University

Bio: Jin-Han Xie is an Assistant Professor in the Department of Mechanics and Engineering Science, College of Engineering at Peking University. He was a Courant Instructor at the Courant Institute of Mathematical Sciences, New York University. Before that, he was a postdoctoral researcher at the physics department of the University of California, Berkeley. He obtained his PhD degree in Applied and Computational Mathematics at the School of Mathematics of the University of Edinburgh in 2015. He got his Bachelor’s degree in Theoretical and Applied Mechanics at the College of Engineering, Peking University in 2011.

Jin-Han Xie's research focuses on fluid dynamics, in particular, geophysical fluid dynamics, turbulence, magnetohydrodynamics and wave-mean flow interaction.

Third-order structure function beyond the inertial range in homogeneous isotropic turbulence.

In 1941, Kolmogorov proposed the 4/5 law for the inertial range in three-dimensional isotropic turbulence, which links measurable third-order structure functions with energy transfer. The inertial-range theories are applied to quantify the direction and magnitude of energy transfer in natural turbulence. However, the applicability of these theories is limited due to the effects of forcing scale and bidirectional energy transfer. Thus, expressions for structure functions beyond the inertial range are required. We derive a forcing-scale-resolving global expression that captures the bidirectional energy transfer. We apply this expression to analyse the drifter data in the Gulf of Mexico and provide evidence for bidirectional energy transfer in ocean turbulence. Also, this new expression implies a conjugate regime to Kolmogorov's theory for the scales larger than the forcing scale in three-dimensional homogeneous isotropic turbulence. This new regime points out the importance of the energy injection even in the large scales, which was believed to be described by absolute equilibrium because of zero averaged energy flux across scales, and potentially provides a foundation for superresolution.



12:00 (GMT+3)
Nikolaj N. Smirnov Nikolaj N. Smirnov
Lomonosov Moscow State University

Bio: Nikolaj N. Smirnov is a professor at the Department of Gas and Wave Dynamics of Lomonosov Moscow State University since 1994. He graduated from the Faculty of Mechanics and Mathematics of MSU in 1976 and became Doctor of Physical and Mathematical Sciences in 1990. Prof. Smirnov is the Corresponding Member of the Russian Academy of Natural Sciences (1998), a member of the Combustion Institute (1992), a member of the Russian National Committee on Theoretical and Applied Mechanics (2001), a member of the International Academy of Astronautics (2005). He was awarded the M.V. Keldysh Medal and the S.P. Korolev Medal (Federation of Astronautics of Russia).

Research interests: dynamics of physically and chemically transforming multiphase media, fundamental problems of ecology, mathematical modeling of the evolution of space debris, and traffic flow. He has published over 200 scientific papers. 15 Ph.D. and 2 doctoral dissertations were defended under his supervision.

Fluid mechanics and its application for describing basic processes in nature, technology and society.

The lecture provides some examples of successful application of fluid mechanics methods and approaches for predictive mathematical modeling of basic processes in nature, technology and social aspects, in particular: Global processes in the Universe: formation of supernovae, interactions of molecular clouds; Ecology of near-Earth space, ensuring flight safety; Modeling of processes in power plants and engines of various types; Modeling the effectiveness of fire and explosion safety measures; Predictive modeling of traffic flows, evaluation of the effectiveness of various control strategies.

 The meeting will be held in the form of a webinar on the Zoom platform.

Pre-registration for the event is not required.

Link to the conference:

Meeting ID : 819 2390 9450