ABSTRACT

Second-order wave effects in floating offshore wind turbines (FOWTs) are consistently under-estimated by mid-fidelity modeling software when compared to experimental data. This research focuses on tuning second-order FOWT hull motions using a parametric study with new features in OpenFAST. The tuning method concentrates on the New England Aqua Ventus (NEAV) VolturnUS semisubmersible hull for a 50-year wave case. The proposed method greatly improves the VolturnUS second-order response when compared to baseline hydrodynamic models.

INTRODUCTION

As climate change and energy security prompt a transition to decarbonized energy, more sources of reliable, local renewable energy are needed. As 40% of the US population lives in coastal counties, offshore wind turbines are an ideal energy source to support this transition (NOAA 2018). Specifically, floating offshore wind turbines (FOWTs) are key for approximately two-thirds of the US offshore wind energy potential due to deep waters off the US coastline (Office of Energy Efficiency and Renewable Energy 2022).

FOWT hull designs have largely borrowed from floating offshore structure designs created for the oil and gas industry, and the hydrodynamics of these oil and gas platforms has been extensively studied through mathematical models, simulations, scale model testing, and ocean testing (Burke 1970; Zhu and Jinping 2011; Watts and Faulkner 1968; Odijie, Wang, and Ye 2017). Three-column semisubmersibles like the design of the platform in this study have existed for over 50 years, such as the Sedco-135 platform and more recently the ATP Titan MiniDOC 3 platform (Pounds and Zaruby 1966; Odijie 2017). This testing has greatly informed the design and testing of FOWTs. However, oil and gas platform hulls differ from FOWT hulls in many ways that affect the hull motion. For example, viscous effects are more important for FOWTs due to the smaller characteristic lengths of the submerged structural components as compared to oil and gas hulls (Roald, Jonkman, Robertson, and Chokani 2013). Therefore, FOWT designs require further modeling research and model testing.

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