Trajectory encounter volume as a diagnostic of mixing potential in fluid flows
Citable URI
https://hdl.handle.net/1912/9007As published
https://doi.org/10.5194/npg-24-189-2017DOI
10.5194/npg-24-189-2017Abstract
Fluid parcels can exchange water properties when
coming into contact with each other, leading to mixing. The
trajectory encounter mass and a related simplified quantity,
the encounter volume, are introduced as a measure of the
mixing potential of a flow. The encounter volume quantifies
the volume of fluid that passes close to a reference trajectory
over a finite time interval. Regions characterized by a
low encounter volume, such as the cores of coherent eddies,
have a low mixing potential, whereas turbulent or chaotic regions
characterized by a large encounter volume have a high
mixing potential. The encounter volume diagnostic is used
to characterize the mixing potential in three flows of increasing
complexity: the Duffing oscillator, the Bickley jet and
the altimetry-based velocity in the Gulf Stream extension region.
An additional example is presented in which the encounter
volume is combined with the u approach of Pratt et
al. (2016) to characterize the mixing potential for a specific
tracer distribution in the Bickley jet flow. Analytical relationships
are derived that connect the encounter volume to the
shear and strain rates for linear shear and linear strain flows,
respectively. It is shown that in both flows the encounter volume
is proportional to time.
Description
© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nonlinear Processes in Geophysics 24 (2017): 189-202, doi:10.5194/npg-24-189-2017.
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