Transport in fluid flows unveiled by Lagrangian Structures

The interpretation of flows in steady systems is straightforward: streamlines and trajectories coincide. Unsteady flows are much more challenging. A natural framework is the Lagrangian one since it allows the study of the flow in terms of particle trajectories. Mixing, i.e. dispersion, plays a fundamental role from this point of view. A usual approach consists in the computation of Lagrangian statistics as absolute and relative dispersion.