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Session: Thermally driven turbulence 2
Session starts: Thursday 27 August, 15:00
Presentation starts: 15:30
Room: Room H

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Riccardo Togni (DIN, Università di Bologna, Forlì, Italy)
Andrea Cimarelli (DISMI, Università degli Studi di Modena e Reggio Emilia, Reggio Emilia, Italy)
Elisabetta De Angelis (DIN, Università di Bologna, Forlì, Italy)

Abstract:
We report the results from two distinct direct numerical simulations (DNS) of turbulent Rayleigh-Bénard convection (RBC) for Rayleigh number of 10^5 and Prandtl number of 0.7 in a laterally unbounded domain confined between two horizontal isothermal plates with no-slip and free-slip boundary conditions respectively. The central aim of the present work consists in a simultaneous description of both flows in a compound physical/scale space domain by using a generalized form of the classical Kolmogorov equation for the second-order velocity structure function. It has been found that the dynamics of the coherent structures in RBC, the so-called thermal plumes, are clearly reflected in the multi-scale energy budgets. In particular, the enlargement of thermal plumes following the impingement at the wall entails a transfer of scale-energy from small turbulent scales toward larger ones. This aspect shed light on the role of thermal plumes in turbulent RBC and could have a direct impact on future attempts to model the effects of small-scale motions in thermal convection.