Fig. 2: Transient attracting profiles (TRAPs).
From: Search and rescue at sea aided by hidden flow structures
a Deformation of a fluid patch close to a saddle stagnation point in a steady flow (left), and to an objective saddle point in an unsteady flow (right). Over short times, a fluid patch aligns with the repelling OECS, and squeezes along the attracting OECS, which both evolve over time. Attracting (Repelling) OECSs are everywhere tangent to the eigenvector field e2 (e1) of the rate-of-strain tensor, with their cores located at minima of the smallest eigenvalue s1. b Attracting OECSs, i.e. TRAPs, in an unsteady ocean velocity data set derived from satellite altimetry data along with their normal attraction rate s1 encoded in the colorbar. TRAPs are hidden to instantaneous streamlines (black). c Illustration of a TRAP evolving in time and attracting within a few hours floating objects whose uncertain initial locations are represented by a square set of white dots.
