BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:George Haller (ETH Zurich) DTSTART:20200630T144500Z DTEND:20200630T160000Z DTSTAMP:20260404T121141Z UID:GDMSeminar/4 DESCRIPTION:Title: Objective material barriers to the transport of momentum and vorticity< /a>\nby George Haller (ETH Zurich) as part of Geometry\, Dynamics and Mech anics Seminar\n\n\nAbstract\nI discuss a recent theory for material surfac es that maximally inhibit the diffusive transport of a dynamically active (i.e.\, velocity-dependent) vector field\, such as the linear momentum\, t he angular momentum or the vorticity\, in three-dimensional unsteady flows . These diffusion barriers provide physics-based\, observer-independent bo undaries of dynamically active coherent structures. Instantaneous limits o f these Lagrangian diffusion barriers mark objective Eulerian barriers to short-term active transport. I show how active diffusion barriers can be identified with active versions of Lagrangian coherent structure (LCS) dia gnostics. In comparison to their passive counterparts\, however\, active L CS diagnostics require no significant fluid particle separation and hence provide substantially higher-resolved Lagrangian and Eulerian coherent str ucture boundaries from shorter velocity data sets. I illustrate these resu lts on two-dimensional turbulence and three-dimensional wall-bounded turbu lence.\n LOCATION:https://researchseminars.org/talk/GDMSeminar/4/ END:VEVENT END:VCALENDAR