[seminar] Split energy cascade in turbulent thin fluid layers by Dr. Stefano Musacchio, Universite' de Nice Sophia-Antipolis

Abstract:

In this seminar I will discuss the entanglement of two-dimensional and three-dimensional dynamics which occurs in turbulent flows confined in thin fluid layers. The behavior of turbulent flows is remarkably affected by their dimensionality. In three dimensions, the nonlinear interaction between different scales is described by the Kolmorogov-Richardson direct cascade: the kinetic energy injected at large scale by an external forcing is transferred to small-scale eddies and it is dissipated by viscosity. By contrast, in two dimensions the simultaneous conservation of kinetic energy and enstrophy results in an inverse energy cascade, i.e., the energy is transferred to large-scale eddies. When the turbulent flow is confined in a thin layer, it is possible to observe an intermediate regime in which both the direct and inverse energy cascades coexist. The flux of energy splits in two parts: a fraction of the energy is transferred toward the large scales, while the remnant energy is transferred to small scales.I will present the results of numerical simulations of the Navier-Stokes equations which highlights the mechanisms of this phenomenon. In particular, I will show that the inverse energy cascade is associated with a suppression of the enstrophy production in an intermediate range of scales.

Biography

Dr. Stefano Musacchio obtained his PhD in Physics at the University of Turin (Italy) in 2004, under the supervision of Prof. Guido Boffetta. From 2004 to 2007 he performed postdoctoral studies at the University of Rome "La Sapienza" (Italy), at the Institut Non Linéaire de Nice (France), and at the Weizmann Institute (Israel). From 2007 to 2009 he has been researcher at the University of Turin (Italy). Since 2009 he is researcher at the University of Nice (France). The research activity of Dr. Musacchio is focused on theoretical and numerical studies of turbulent flows, with a special interest for turbulent dynamics in two-dimensions.