Dense lagrangian particle tracking of turbulent rayleigh bénard convection in a cylindrical sample using Shake-The-Box

Abstract

We present spatially and temporally resolved velocity and acceleration measurements of turbulent Rayleigh-Bénard convection covering the complete volume of a cylindrical sample with aspect ratio one. Using the Shake-The-Box Lagrangian particle tracking algorithm, we are able to instantaneously track up to ~ 600,000 particles in the complete sample volume (~ 1 m³). The data assimilation scheme FlowFit with continuity and Navier-Stokes-constraints is used to interpolate the scattered velocity and acceleration data by continuous 3D B-Splines in a cubic grid, enabling to recover the smallest flow scales. The frame rate was chosen to be at least 7 times faster than the Kolmogorov time scale. In the presentation, we show Lagrangian and Eulerian visualizations of the large scale circulation (LSC) as well as small scale structures, such as thermal plumes and turbulent background fluctuations and unveil the dynamics of their complex interplay. Rare dynamic events, such as cessations and reo rientations of the LSC will be presented in addition to combined and conditioned Lagrangian and Eulerian statistics of turbulent quantities.