Numerical Modelling of Dynamic Responses of a Floating Offshore Wind Turbine Subject to Focused Waves

Zhou Zhou,Li Li,Peyrard Peyrard,Pan Pan,Incecik Incecik,Xiao Xiao,Liu Liu

doi:10.3390/en12183482

Abstract

In this paper, we present numerical modelling for the investigation of dynamic responses of a floating offshore wind turbine subject to focused waves. The modelling was carried out using a Computational Fluid Dynamics (CFD) tool. We started with the generation of a focused wave in a numerical wave tank based on a first-order irregular wave theory, then validated the developed numerical method for wave-structure interaction via a study of floating production storage and offloading (FPSO) to focused wave. Subsequently, we investigated the wave-/wind-structure interaction of a fixed semi-submersible platform, a floating semi-submersible platform and a parked National Renewable Energy Laboratory (NREL) 5 MW floating offshore wind turbine. To understand the nonlinear effect, which usually occurs under severe sea states, we carried out a systematic study of the motion responses, hydrodynamic and mooring tension loads of floating offshore wind turbine (FOWT) over a range of wave steepness, and compared the results obtained from two potential flow theory tools with each other, i.e., Électricité de France (EDF) in-house code and NREL Fatigue, Aerodynamics, Structures, and Turbulence (FAST). We found that the nonlinearity of the hydrodynamic loading and motion responses increase with wave steepness, revealed by higher-order frequency response, leading to the appearance of discrepancies among different tools.

Highlights

One of the main challenges for floating offshore wind turbines (FOWT) installed in moderate depth and deep-water sites is the increased maintenance and operation costs due to the structural damage of the FOWT system under severe environmental conditions
Several experimental campaigns examining the responses of FOWT to wave loads have been carried out [1,2,3]
Unlike our previous work [9,11,14], which was focused on regular waves, here, we extend the study to focused waves and engage in a range of wave parameters

Summary

Introduction

One of the main challenges for floating offshore wind turbines (FOWT) installed in moderate depth and deep-water sites is the increased maintenance and operation costs due to the structural damage of the FOWT system under severe environmental conditions. The most critical issue for the design is how to accurately predict the hydrodynamic loading and structural dynamic response of the floating platform, the tension loads of the mooring system and aerodynamic responses of the wind turbine. Most existing experimental FOWT models are designed and manufactured by keeping the Froude number the same, in which the ratio between the inertial and the gravity force is identical between the scaled model and full-scale prototype. In this situation, the Reynolds number is not the same. Muller et al [4]

Methods

Results

Conclusion