NumbaCS: A fast Python package for coherent structure analysis

NumbaCS (Numba Coherent Structures) is a Python package that efficiently implements a variety of methods for studying material transport in time-dependent fluid flows.It leverages Numba -a high performance Python compiler for generating optimized machine code from Python functions -along with other Numba-compatible packages behind the scenes, producing fast and user-friendly implementations of coherent structure methods."Coherent structure methods" refer to any method that can be used to infer or extract Lagrangian and objective Eulerian coherent structures.The theory behind these methods has been developed over the last few decades with the aim of extending many of the important invariant objects from time-independent dynamical systems theory to the more general setting where a system may have arbitrary time dependence and may only be known or defined for some finite time.These time-dependent systems are ubiquitous in the context of geophysical and engineering flows where the evolution of the velocity field depends on time and velocity data representing these flows is not available for all time.By extending the ideas from the time-independent setting to the more general time-dependent setting, important transient objects (coherent structures) that govern how material is transported within a flow can be identified.Understanding material transport in flows is of great importance for applications ranging from monitoring the transport of a contaminant in the ocean or atmosphere to informing search and rescue strategies for persons lost at sea.