Mixing in a meandering jet: A Markovian approximation

Mixing and transport in correspondence of a meandering jet are investigated . The large-scale flow held is a kinematically assigned streamfunction. Two basic mixing mechanisms are considered separately and in combination: dete rministic chaotic advection induced by a time dependence of the flow, and t urbulent diffusion described by means of a stochastic model for particle mo tion. Rather than looking at the details of particle trajectories, fluid exchange is studied in terms of Markovian approximations. The 2D physical space acc essible to fluid particles is subdivided into regions characterized by diff erent Lagrangian behavior. From the observed transitions between regions it is possible to derive a number of relevant quantities characterizing trans port and mixing in the studied flow regime, such as residence times, meridi onal mixing, and correlation functions. These estimated quantities are comp ared to the corresponding ones resulting from the actual simulations. The o utcome of the comparison suggests the possibility of describing in a satisf actory way at least some of the mixing properties of the system through the very simplified approach of a first-order Markovian approximation, whereas other properties exhibit memory patterns of higher order.