Abstract:

Experiments on vortex-induced vibration suppression devices were carried out at a canal. Helical wire type and flag type suppression devices were attached to a cable 17.45 meters in length and 28.6 millimeters in diameter. The effectiveness of the suppression devices was measured in uniform and sheared flow, as well as under different tension. Vortex-induced vibration mechanisms of the related suppression devices were also studied.

Introduction

With the development of offshore technology, vortex-induced vibration has become an important consideration in the design and operation of mooring lines and ocean structures. Vortex-induced vibration can cause mechanical failure of ocean structures as well as create noise which deteriorates the signal transmission of instruments in underwater environments. Separate aspects of the mechanism, such as shedding frequency, drag and lift force, pressure distribution, hydrodynamic damping resonance With the structure, and coherence of the Vibration have been extensively studied. However, because of the complex interaction between structural properties and the fluid mechanisms, a satisfactory analytical model sufficient for engineering implementation is not currently available. It is well known that vortex vibration can be suppressed by various structural and hydrodynamic means. Some of the suppression devices, which have been developed during wind-induced vibration studies, can be adopted to the vortex-induced vibration in marine field, with some reservations. Many of the scattered experimental results on suppression devices, which have been mainly obtained at the laboratory level, are useful for initial feasibility studies. However, for actual applications, it is prudent to implement the suppression device after an experimental confirmation to ensure successful performance. Some of the successful application examples on drill casings and mooring lines for instruments are found in (1 - 4). This paper evaluates the performance of helical wire and flag type suppression devices, and studies mechanisms of vortex-induced suppression devices in marine environments.

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