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Objective Eulerian Coherent Structures in Fluids

Speaker: George Haller
[Announcement (PDF)]

Speaker Affiliation: Professor of Nonlinear Dynamics
Institute for Mechanical Systems
ETH Zurich
Zurich, Switzerland

Date: Tuesday January 24, 2017 at 11 a.m in 5-314

Short-term variability in coherent features of unsteady fluid flows is  of prime interest in fields ranging from flow control through environmental assessment to search and rescue operations. Available methods for the identification of the instantaneously most influential flow structures, however, are generally  frame-dependent and heuristic, which limits the reliability of the results they provide.  In this talk, we discuss a rigorous global variational theory of objective Eulerian Coherent Structures (OECSs), which uncovers the correct instantaneous material skeleton of an unsteady fluid  flow in a frame-invariant fashion.  We show applications to detecting unsteady  flow structures objectively in satellite-based and radar-inferred ocean surface velocity fields. We find that these structures remain generally hidden to traditional, non-objective Eulerian flow analysis.