1. Title : The aero-hydrodynamic interference impact on the NREL 5-MW floating

wind turbine experiencing surge motion

2. Authors : 

Ali Alkhabbaz a,*, Hudhaifa Hamza b, Ahmed M. Daabo b, Ho-Seong Yang c, Min Yoon d,

Aisha Koprulu e, Young-Ho Lee ca Mechanical Engineering Department, College of Engineering, University of Mosul, Mosul, 41002, Iraq b Mining Engineering Department, College of Petroleum and Mining Engineering, University of Mosul, Mosul, 41002, Iraq

c Center for Offshore Wind & Green Hydrogen Ammonia Research, Korea Maritime and Ocean University, Busan, 49112, South Korea d Mechanical Engineering Department, Korea Maritime and Ocean University, Busan, 49112, South Korea

e Aeronautical Technical Engineering Department, Technical College, Al- Kitab University, Kirkuk, 36001, Iraq

3. Journal : Ocean Engineering 295 (2024) 116970

4. Abstract:

The present work seeks to explore how the surge response of a semi-submersible platform affects the aerodynamic performance and wake properties of a 5-MW Floating Offshore Wind Turbine (FOWT) when subjected to fully coupled wind-wave load conditions. In order to attain a more comprehensive understanding of the impact of platform surge displacement, a comparative analysis of the aerodynamic performance and wake characteristics was conducted. This analysis involved comparing a floating turbine experiencing surge motion with a conventional floating turbine operating under stable fixed-platform conditions. This simulation employs an overset mesh technique to accurately capture the impact of the semi-submersible platform’s surge response on both the aerodynamic behavior and wake properties. Furthermore, the integration of Dynamic Fluid Body Interaction (DFBI) and Volume of Fluid (VOF) approaches is utilized to precisely understand the aerohydrodynamic interaction and simulate the water-air interface surface. A thorough analysis was conducted to assess aerodynamic performance, catenary analysis, and hydrodynamic reactions by comparing the results obtained from CFD simulations with those acquired from the FAST and OrcaFlex codes. The CFD findings indicate a significant impact of the platform surge response on the apparent wind velocity perpendicular to the rotor plane, which arises from the combined effects of the incoming wind velocity and surge-induced velocity. Moreover, the velocity recovery of the wake flow downstream of the rotor is faster during surge motion than that of the fixed bottom turbine. The importance of this finding is especially relevant in wind farm scenarios marked by diminished aerodynamic interference between adjacent turbines. Furthermore, CFD investigations and visualizations are carried out on shedding vortices in the wake, tower-blade tip interference, and tension force of the mooring lines. These aspects cannot be adequately captured using potential codes.