Source: Max Planck Institute for Dynamics and Self-Organization
Turbulent flows are paradigmatic examples of systems that are very far from statistical equilibrium. This is associated with the fact that turbulent flows involve a very wide range of spatial and temporal scales that interact and exchange energy and momentum, possessing net fluxes of energy and other quantities across the scales.
A problem of interest is to understand the ways in which this irreversibility is felt by particles that are being transported and mixed by the turbulent flow. Are the forward and backward in time mixing properties of the particles the same or different? Can we understand at a detailed level the mechanisms responsible for such Lagrangian irreversibility in turbulence?
The problem is not only of fundamental, but also applied interest since forward and backward in time mixing and transport properties of particles in turbulence are each of importance to a range of distinct physical processes.
We have conducted a number of theoretical and computational investigations into this problem, considering how particle inertia and the dimensionality of the turbulent flow affect the irreversibility of their motion, with some surprising findings. More details can be found in the listed publications.