Experimental analysis of Rayleigh-Bénard convection in a cylindrical cell by tomographic PIV

This paper presents an experimental investigation of Rayleigh-Bénard convection in both rotating and non- rotating conditions. Rayleigh-Bénard convection, the fluid flow driven by temperature gradients parallel to the gravity, is relevant to a great variety of physical phenomena, ranging from motions in the atmosphere and the oceans to convection in the interior of planets and stars. In many of these applications, the interplay between a background rotation and the thermal convection has a key role in the fluid dynamic behaviour of the system. In the present work, the time-resolved tomographic particle image velocimetry (PIV) is used to investigate the whole domain of Rayleigh-Bénard convection inside a cylinder with aspect ratio equal to 1/2 at Rayleigh and Prandtl numbers equal to 1.86 ×10^8 and 7.6, respectively. The effects of rotation on the flow dynamics and evolution are also investigated in similar operating conditions at two different Rossby numbers, namely 0.25 and 0.1. The behaviour of the turbulent flow is analyzed both in the time-average and instantaneous evolution with focus on the large scale structures of the flow. Modal decomposition techniques are also used to identify the characteristic modes of the thermal convection.