Numerical simulations of island wakes downstream Green Island, Taiwan due to passing of Kuroshio

Kuroshio-induced island wake downstream the 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 number 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 and 1.92 from satellite images, and 1.29 and 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. Magnitude of the propagation speed of the vortices is found to be the same order as that of the Kuroshio, implying the nonlinearity as well as interactions of vortices and the Kuroshio are strong. Coriolis force does affect the free-surface distribution, however, its effect on vortices and flow field is insignificant.