Lagrangian Coherent Sets as transport barriers in convection1JOERG SCHUMACHER, PHILIPP VIEWEG, TU Ilmenau, CHRISTIANESCHNEIDE, KATHRIN PADBERG-GEHLE, Leuphana University Lueneburg —
The analysis of the turbulent heat transfer in thermal convection flow is mostlydone in the Eulerian frame of reference. Here, we use an ensemble of more thanhalf a million individual Lagrangian tracer trajectories, which are advected togetherwith the evolving turbulent flow, to identify subsets that contribute least to theheat transfer. These trajectories probe Lagrangian Coherent Sets sets that remainspatially connected for a finite time and evolve in time. The analysis is based onthree-dimensional direct numerical simulations at three different Prandtl numbers.Our Lagrangian analysis results provide a complementary view on the transport andare found to be consistent with the standard Eulerian results.

1 The work is supported by the Priority Programme DFG-SPP 1881 of the DeutscheForschungsgemeinschaft.