Defining coherent structures for flow modeling : identification, dynamical significance, and low-order representation
While a single definition for a coherent structure has been the topic of debate over many years, it can be agreed that the eye is drawn to certain motions that are persistent in space and time in a range of flows. Here we investigate flow-specific descriptions of coherence associated with specific scientific questions and practical applications. After discussing the identification and classification of important structure types, we outline building block models for each in wall-bounded turbulence. Simple theoretical rules governing the forcing that sustains the structures are compared with data-driven characterization of key nonlinear interactions. The results are used to outline a skeleton for coherent structures that, for example, can be used to improve the representation of the wall region in wall-modeled LES, as well as to understand sustaining mechanisms in wall turbulence in a manner amenable to reduced-order modeling. As time permits, related investigations in other flow configurations and additional lab activities will be described.
Contact Nathanaël Machicoane for more information or to schedule a discussion with the seminar speaker.