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Flow topology and scalar mixing in spatially heterogeneous flow fields
Author(s) -
Barros Felipe P. J.,
Dentz Marco,
Koch Jonas,
Nowak Wolfgang
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl051302
Subject(s) - scalar (mathematics) , mixing (physics) , vorticity , mixing patterns , physics , flow (mathematics) , entropy (arrow of time) , mechanics , statistical physics , vortex , geometry , mathematics , thermodynamics , quantum mechanics
Scalar mixing plays a significant role for transport in geophysical flows because it controls dilution and is a main driver for many chemical reactions. Here we study the local scale flow mechanisms that lead to enhanced scalar mixing, and how they impact on the global mixing behavior. Mixing is quantified in terms of the entropy of the scalar distribution. It is shown that the evolution of entropy is directly linked to the flow topology in terms of the Okubo‐Weiss parameter Θ. Dominant shear and stretching deformation (Θ > 0) leads to a strong increase of local mixing strength, while dominant vorticity (Θ < 0) has only a minor impact. This allows to delineate regions of increased scalar mixing potential by mapping out the spatial distribution of Θ( x ), and to relate global scalar mixing to an areal averaged effective Okubo‐Weiss measure.