An Experimental Study of Lagrangian Statistics in Rayleigh-B\'enard Convection*

We present an experimental study of Lagrangian statistics in Rayleigh-B\'enard convection, using water as the working fluid. The tracking volume is (5 cm)$^{3}$ in the centre of a cylindrical shaped convection cell of aspect ratio one and 20 cm in height. Three cameras were used to identify the 3-dimensional positions of the tracer particles, which were evenly suspended in the cell. Detailed properties of the particle velocity, acceleration and dispersions along different directions have been investigated. We also studied the dependency of pair dispersion properties on the initial pair separation. All these properties have been examined with Rayleigh number spanning from $10^8$ to $10^{10}$ and Prandtl number around 6.2.