LCS Tool: A computational platform for Lagrangian coherent structures

• New computational platform facilitates detection of Lagrangian coherent structures (LCSs) from their geodesic theory with minimal effort.
• Step by step explanation of LCS algorithms.
• Three examples featuring analytic flow models and experimental flow data demonstrate software usage.

We give an algorithmic introduction to Lagrangian coherent structures (LCSs) using a newly developed computational engine, LCS Tool. LCSs are most repelling, attracting and shearing material lines that form the centrepieces of observed tracer patterns in two-dimensional unsteady dynamical systems. LCS Tool implements the latest geodesic theory of LCSs for two-dimensional flows, uncovering key transport barriers in unsteady flow velocity data as explicit solutions of differential equations. LCS Tool makes theoretical results accessible to the fluid mechanics community since implementing these results directly could be time consuming. After a review of the underlying theory, we explain the steps and numerical methods used by LCS Tool, and illustrate its capabilities on three unsteady fluid flow examples.