Lagrangian tracer dynamics in a closed cylindrical turbulent convection cell

TL;DR

This study investigates how large-scale circulations influence Lagrangian tracer dynamics in turbulent Rayleigh-Benard convection within cylindrical cells, revealing aspect ratio effects on particle dispersion and acceleration statistics through direct numerical simulations.

Contribution

It provides the first detailed analysis of Lagrangian tracer dynamics across varying aspect ratios in turbulent convection using high-resolution simulations.

Findings

Lagrangian dispersion depends on aspect ratio.

Acceleration statistics are affected by large-scale circulations.

Results align qualitatively with laboratory experiments.

Abstract

Turbulent Rayleigh-Benard convection in a closed cylindrical cell is studied in the Lagrangian frame of reference with the help of three-dimensional direct numerical simulations. The aspect ratio of the cell Gamma is varied between 1 and 12, and the Rayleigh number Ra between 10^7 and 10^9. The Prandtl number Pr is fixed at 0.7. It is found that both the pair dispersion of the Lagrangian tracer particles and the statistics of the acceleration components measured along the particle trajectories depend on the aspect ratio for a fixed Rayleigh number for the parameter range covered in our studies. This suggests that large-scale circulations present in the convection cell affect the Lagrangian dynamics. Our findings are in qualitative agreement with existing Lagrangian laboratory experiments on turbulent convection.