The beauty of turbulent convection: A particle tracking endeavor

Abstract

We present spatially and temporally resolved velocity measurements of turbulent Rayleigh-Bénard convection (RBC) covering the complete volume of a cylindrical sample with aspect ratio one. Using the Shake-The-Box (STB) Lagrangian particle tracking (LPT) algorithm, we are able to instantaneously track up to ~ 600,000 particles in the complete sample volume (~ 1 m³), corresponding to mean inter-particle distances of 8 Kolmogorov lengths. 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 (see Movie) 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.