Coupled Aero-Hydrodynamic Analysis on a Floating Offshore Wind Turbine Under Extreme Sea Conditions
- Yang Huang (Shanghai Jiao Tong University) | Decheng Wan (Shanghai Jiao Tong University) | Changhong Hu (Kyushu University)
- Document ID
- International Society of Offshore and Polar Engineers
- The 27th International Ocean and Polar Engineering Conference, 25-30 June, San Francisco, California, USA
- Publication Date
- Document Type
- Conference Paper
- 2017. International Society of Offshore and Polar Engineers
- aero-hydrodynamics, extreme sea conditions, couple effects, floating offshore wind turbine, unsteady actuator line model
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- 23 since 2007
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To develop renewable energy, the offshore wind energy technology has become an attractive research field. Considering the coupling effect of the platform motions and aerodynamic loads, how to accurately simulate the aero-hydrodynamics of floating offshore wind turbine is important. In this paper, an unsteady actuator line model (UALM) coupled with a two-phase CFD solver called naoe-FOAM-SJTU is applied to solve the three-dimensional Navier-Stokes equations to focus on the coupled dynamic responses of an aerodynamics-hydrodynamics-mooring system for a floating offshore wind turbine named OC3-HywindSpar under extreme sea conditions. Response characteristics including the thrust and the rotor power of the wind turbine, the motions of the platform and the mooring loads under different extreme sea states are carefully compared to study the influence of the wind speed and the wave height on the floating offshore wind turbine. Furthermore, several conclusions are drawn based on the comparison results.
The increasing demand for energy and the environmental issues make the exploitation and research of new energy sources more necessary (Morato, Sriramula, Krishnan, and Nichols, 2017). As a clean renewable energy, Wind power with huge reserve is promising. The development of offshore wind power is quickly in recent years, for offshore wind is steadier and stronger than overland wind (Petersen et al., 2014). And the offshore wind energy technology has become an attractive research field in the world. Due to the complexity and particularity of ocean environment, the loads exposed on offshore wind turbines, especially on floating offshore wind turbines, are more complex than onshore wind turbines. And considering the coupling effect of the platform motions and aerodynamic loads, integrated analysis considering stochastic and wind actions for floating offshore wind turbine is challenging. So it is important to accurately simulate the aero-hydrodynamics of floating offshore wind turbine under extreme sea conditions.
It is necessary to research the coupling performance of the floating offshore wind turbine under extreme sea conditions, and some studies focusing on different aspects have been performed. Nielsen, Hanson, and Skaare (2006) combined two independent computer programs SIMO/RIFLEX and HAWC2 to a coupled simulation tool for the simulation of the dynamic response of floating wind turbines exposed to forces form wind, wave and current, and it was tested and verified to be accurate in the simulation of the performance of the whole system. M Karimirad, and Moan (2012) analyzed coupled wave and wind-induced motions of spar-type 5-MW wind turbines under operational and extreme sea states. Advanced blade element momentum theory was used to study the aerodynamics. It was found that the wind turbulence had little influence on the dynamic motion and structural responses, while it had a significant impact on power production. And the mean value of the dynamic responses of the platform was mainly induced by the wind. Muliawan, Karimirad, Gao, and Moan (2013) considered a combined concept involving a spar-type floating wind turbine and an axis-symmetric two-body wave energy converter denoted as STC, and they studied wave-wind induced response of the STC system under ultimate limit states. Coupled analysis was performed using the SIMO/TDHMILL in the time domain to investigate the force characteristics under extreme conditions. It should be noted that the wind turbine was parked under extreme conditions. It was found that the extreme responses were considered to be primarily governed by wave induced response. And the extreme responses on the mooring line and on the bending moment at the spar-tower interface increased owing to the addition of a Torus on the floating wind turbine. M Karimirad, Gao, and Moan (2009) investigated the coupled wave and wind induced dynamic motions of the catenary moored spar floating wind turbine in harsh conditions. The DeepC code was used to calculate the displacement force of mooring lines, and dynamic motion of the system due to wave in harsh condition was considered in HAWC2. It was found that the coupled dynamic response in harsh conditions was dominated by wind induced response. And constant wind excited the pitch natural frequency, while turbulent wind excited both surge natural frequency and pitch natural frequency. In addition, increasing the hydrodynamic damping could reduce the pitch resonance response. Ma, Hu, and Xiao (2015) discussed the effects of loads induced by wind and wave on a spar-type floating wind turbine, and the response characteristics of motions and mooring loads of the system under operational and extreme sea states were evaluated.
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