ABSTRACT:

Numerical simulations were performed for the evaluation of wave and current loads on fixed cylindrical platform model for ocean wind turbine using ANSYS-CFX package. The numerical wave tank was actualized by specifying velocity at the inlet and applying momentum loss as wave damper at the end of the wave tank. Volume-Of-Fluid (VOF) scheme was adopted to capture the air-water interface. Accuracy validation of numerical wave tank with truncated vertical circular cylinder had been accomplished by comparing the CFD results with Morison's formula and the experimental data. The parametric study has been carried out by varying the wave length and amplitude alternatively. As a meaningful engineering application, in the present study, three kinds of conditions have considered, i.e. the cases with current, waves and the combination of current and progressive wave, respectively, passing through a cylindrical platform model. It was found that CFD results show reasonable agreement with experimental data and Morison's formula when only progressive wave is considered, however, when current is included, CFD gives smaller load than Morison's formula.

INTRODUCTION

Wind turbine foundations installed at offshore sites are subject to ocean waves and current directly. Recently the structural integrity of Ocean Wind Turbine (OWT) foundation draws much attention as renewable wind energy market grows. As the main component to the wind turbine system, cylindrical foundation has been widely used. Flow around circular cylinders has been a research topic in fluid mechanics for decades because of its complex physical phenomena, such as separation and vortex shedding, deformation of incoming wave. For a planar oscillatory flow around a circular cylinder, there are many experimental and numerical studies, providing the basic knowledge to further understand complex flow environments, such as the combination of oscillatory flow by incoming wave and current-induced vortex shedding.

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