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Vortex generation in oscillatory canopy flow
Author(s) -
Ghisalberti Marco,
Schlosser Tamara
Publication year - 2013
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/jgrc.20073
Subject(s) - vortex , canopy , instability , mechanics , reynolds number , flow (mathematics) , flow visualization , physics , mixing (physics) , meteorology , turbulence , geology , geography , archaeology , quantum mechanics
In this paper, we demonstrate for the first time the generation of coherent vortices at the top of a canopy in oscillatory (i.e., wave‐dominated) flow. Through a series of flow visualization experiments, vortex formation is shown to occur when two conditions described by the Keulegan–Carpenter ( KC ) and Reynolds ( Re ) numbers are met. First, the wave period must be sufficiently long to allow the generation of the shear‐driven instability at the top of the canopy; this occurs when KC ≳ 5. Second, the vortex instability must be able to overcome the stabilizing effects of viscosity; this occurs when Re ≳ 1000. The vortices greatly increase the rate of vertical mixing within the canopy, such that any prediction of residence time in a coastal canopy requires an understanding of whether vortex generation is occurring.