Spatial-temporal scales of Green Island wake due to passing of the Kuroshio current
The Kuroshio current-induced island wake downstream of Green Island, Taiwan, is studied using satellite imagery and a depth-averaged shallow-water model. Spatial–temporal scales, such as aspect ratio, dimensionless width, and Strouhal number, as well as propagation speed of the vortices, are quantified for Reynolds numbers 100, 200, and 500, respectively. It is found that the aspect ratio is between 1.76 and 2.72 obtained from satellite images and between 3.50 and 3.72 from numerical simulations. The dimensionless width is in the range of 1.84 to 1.92 from satellite images, and 1.29 to 1.33 from numerical modelling. The Strouhal number is between 0.17 and 0.20 from numerical simulations. Computed results are compared with theory, available satellite imagery, and in situ measurements, and show reasonable agreement. The magnitude of the propagation speed of the vortices is found to be of the same order as that of the Kuroshio, implying non-linearity as well as interactions of vortices, and the Kuroshio is strong. The Coriolis force affects the free-surface distribution, but its effect on vortices and flow field is insignificant.
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Document Type: Research Article
Affiliations: Department of Marine Environmental Informatics, National Taiwan Ocean University, Keelung, 20224, Taiwan
Publication date: June 18, 2014