| Summary: | 碩士 === 國立臺灣海洋大學 === 海洋環境資訊學系 === 101 === A fluid flows past a stationary body is a classical fluid problem. The disturbed flows around body, and transitions from a steady separated flow to periodic shedding of vortices and turbulence also occur frequently in ocean flow downstream of islands. A small island wake downstream of Green Island, Taiwan due to passing of the energetic Kuroshio is numerically studied for Reynolds number 100, 200, and 500. The numerical model is based on the depth-averaged shallow-water equations (SWEs) which are solved with the space-time least-squares finite-element method (STLSFEM). Vortex characteristics, such as spatial scales (aspect ratio and dimensionless width), temporal scale (Strouhal number), and propagation speed of the vortices are quantified. Computed results are compared with in situ measurements or other similar simulation results. Aspect ratio is in the range of 2~2.5, dimensionless width 1~1.1, and Strouhal number 0.16~0.21. These findings agree reasonably with available satellite images and in situ measurements, as well as other reported results. The magnitude of the propagation speed of the vortices is 0.1~0.5 m/s, the same order as that of the Kuroshio, implying that the nonlinearity of vortices as well as the interactions between vortices and the Kuroshio are strong.
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