Abstract

This paper presents the investigation results of the VIM phenomenon, discloses the characteristics of the relative motions of a floating cylinder. Floating circular platforms present a large characteristic diameter associated with a large natural period of motions in the horizontal plane. In this paper, the VIM around floating circular cylinders, m* = 1.0, with very low aspect ratio, L/D = 2, as a motivation for better understanding the VIM of Spar platforms.

In order to study vortex induced motions (VIM) response of a circular cylinder, numerical computations are carried out by our in-house VIM solver vim-FOAM-SJTU. In the CFD simulations the cylinder is moored with linear springs to provide a range of reduced velocities. The fluid domain is gridded by an unstructured grid. The boundary layer is modeled with a first boundary layer y+≈2. The focus is on the effect of reduced velocity on the VIM response. Free decay tests and vortex-induced motion (VIM) tests have been built numerically. The Fourier analysis of the motions have been performed in order to explain in figure-eight-type motion trajectory.

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