Lagrangian heat transport in turbulent three-dimensional convection

Abstract

Spatial regions that do not mix effectively with their surroundings in fully turbulent three-dimensional Rayleigh-B\'enard convection are identified by clusters of Lagrangian trajectory segments. By monitoring a locally defined Nusselt number along these trajectories it is quantified that these Lagrangian coherent sets, which are indicated by the tracer clouds in the figures, contribute significantly less to the global heat transport than their spatial complement where thermal plumes rise and fall.