libcfd2lcs: A general purpose library for computation of Lagrangian coherent structures during CFD simulation

This report describes libcfd2lcs, a general purpose numerical library that performs the calculations needed to extract Lagrangian Coherent Structures (LCS) from time dependent flows. libcfd2lcs is designed to work with two or three dimensional hydrodynamic datasets produced by computational fluid dynamics (CFD) simulations or experimental measurements. Critically, it is capable of interfacing directly with a distributed memory CFD application, allowing for parallel, on-the-fly calculation of LCS. The library has been integrated with several research flow solvers and tested for a variety of flows. The additional computational overhead introduced by the library can vary significantly (4-44% additional wall clock time in our tests) depending on the test/code, which we consider as not prohibitive. The library shows good scaling efficiency (> 80%) for up to 1024 compute cores on ARCHER.