Project: TURB-ROT - Inverse and direct cascades in rotating turbulent flows.

Prace Call: 17th
ID: 2018184374, Leader: Luca Biferale
Affiliation: University of Rome Tor Vergata, IT
Research Field: Engineering
Collaborators: Fabio Bonaccorso University of Rome Tor Vergata IT , Michele Buzzicotti University of Rome Tor Vergata IT , Patricio Clark Di Leoni University of Rome Tor Vergata IT
Resource Awarded: 60 Mil. core hours on Marconi - KNL

Abstract

Turbulent flows under strong rotation exhibit fascinating phenomena which can be appreciated in the might of convective storms, in the awe inspiring swirls in Jupiter’s Big Red Spot, in the beautiful structures seen in experiments and in many other instances. Despite of the huge number of theoretical, numerical and experimental investigations, it is not yet comprehended what are the main dynamical and statistical mechanisms leading to the transition from a quasi-isotropic evolution to a strongly-anisotropic behaviour with elongated structures, as empirically observed when the rotation rate is increased. Rotating turbulence is the result of the intricate interactions between quasi 2D slow motions with 3D fast wave propagations, coupled to strong small-scales turbulent fluctuations. As a result, rotating turbulence develops both the formation of strong columnar cyclonic large-scale condensates and small-scales highly intermittent and non-Gaussian fluctuations, the outcomes of a split-energy cascade both forward and backward. The need to resolve two range of scales, larger and smaller than the injection scale, leads to extremely demanding resources for Direct Numerical Simulations (DNS) approaches. In this project, we aim to study the transition from a forward to a split-energy cascade in rotating turbulence at changing two different control parameters. For fixed aspect ratio, we will perform a refined scanning of the rotation intensity close to the critical one in order to make a definitive statement whether there exists a smooth or a discontinuous jump in the energy flux and clarify the nature of this out-of-equilibrium (phase) transition. Second, for a few selected rotation intensities, we intend to push the vertical size towards the “infinite’ volume limit, in order to understand whether the Wave-Turbulence prediction of a vanishing inverse energy cascade is correct: a theoretical and applied problem open for more than 20 years and never clarified yet. Our results will have impact in problems broader than the case of flows under rotation, as Wave Turbulence is a basic approach for many other configurations, such as internal gravity waves in stratified flows, surface waves, acoustic waves, Alfven waves in conducting flows, to cite just a few of the most important ones.