Fluid & BioDynamics Seminar: From trajectories to transport: network-based approaches for coherent sets and scalar mixing in turbulent flows

Understanding, quantifying and controlling transport and mixing processes are central in the study of fluid flows. Many different Lagrangian approaches have been proposed for detecting organizing flow structures, including recent data-based methods that aim to identify such coherent objects directly from simulated or measured tracer trajectories. Among these approaches are Lagrangian flow networks, where trajectories serve as network nodes and the links are weighted according to spatio-temporal distances between trajectories. Spectral clustering as well as simple network measures such as node degrees or clustering coefficients can be used to identify flow regions of different dynamical behavior. In this talk, we propose some extensions to the network-based framework that allow us (i) to study the long-term
dynamics of coherent sets in turbulent flows and (ii) to describe and quantify the transport and mixing of scalar quantities. We demonstrate our approaches in a number of example systems, including turbulent Rayleigh-Bénard convection flows.