Publication Date:
2022-05-25
Description:
Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Physica D: Nonlinear Phenomena 372 (2018): 31-51, doi:10.1016/j.physd.2018.01.011.
Description:
The notion of a Lagrangian Coherent Structure (LCS) is by now well established
as a way to capture transient coherent transport dynamics in unsteady
and aperiodic fluid flows that are known over finite time. We show that the
concept of an LCS can be generalized to capture coherence in other quantities
of interest that are transported by, but not fully locked to, the fluid.
Such quantities include those with dynamic, biological, chemical, or thermodynamic
relevance, such as temperature, pollutant concentration, vorticity,
kinetic energy, plankton density, and so on. We provide a conceptual
framework for identifying the Generalized Lagrangian Coherent Structures
(GLCSs) associated with such evolving quantities. We show how LCSs can
be seen as a special case within this framework, and provide an overarching
discussion of various methods for identifying LCSs. The utility of this more
general viewpoint is highlighted through a variety of examples. We also show
that although LCSs approximate GLCSs in certain limiting situations under
restrictive assumptions on how the velocity field affects the additional quantities
of interest, LCSs are not in general sufficient to describe their coherent
transport.
Description:
SB acknowledges with thanks support from the Australian
Research Council through Future Fellowship grant FT130100484 and
Discovery Project grant DP170100277. NTO acknowledges support from the
U.S. National Science Foundation under grant CMMI-1563489. IR would like
to acknowledge support from the U.S. NSF grant OCE-1558806, ONR grant
N00014-11-10087 and NASA grant NNX14AH29G.
Keywords:
Lagrangian coherent structures
;
Fluid flow
;
Flow barriers
;
Ocean eddies
;
Atmospheric vortices
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
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