The description of fluid behavior by coherent structures

More insight into the underlying physical mechanisms of fluid flow can be gained by the decomposition and reorganization of gathered data into coherent structures that contribute significantly to the governing temporal and/or spatial processes. By concentrating on these structures a clearer picture emerges that allows the description of complex flow behavior by a reduced set of characteristic structures. This article presented three examples of coherent structures: global stability modes extracted from direct numerical simulations of compressible flow about a swept parabolic cylinder, wavepacket pseudomodes determined from a microlocal analysis of flow near the attachment-line of a swept body, and dynamic modes identified from experimental data of flow in the wake of a flexible membrane within a temporal or spatial framework. Even though the techniques and approximations have varied greatly, the common theme has been the low-dimensional description of fluid behavior as a prerequisite for advancing our understanding of fluid behavior in complex configurations. © 2010 Springer Science+Business Media B.V.