浮體式風力機受風與波浪耦合作用下運動之數值模擬研究

Numerical Study of Spar Type Floating Wind Turbine Motion under the Coupling of Aerodynamic and Hydrodynamic Loads

本論文探討Spar型浮體式風力發電機及Semi-submersible型浮體式風力機受風與波浪耦合作用下運動之數值模擬研究。研究方法為求解雷諾平均那維爾史托克方程式，並選用適當的紊流模型及搭配額外JAVA副程式來考量錨鏈力。風力機部分為NREL 5MW，陸上運轉模擬結果與NREL之資料相驗證，轉子功率計算結果與資料趨勢符合，誤差皆於8%以內。海上運轉模擬部分在均勻風速11.4 m/s，以及波高4m，周期10秒、波向角0度之規則波中進行縱搖運動及同時開放縱移、起伏及縱搖三自由度運動。由模擬結果顯示浮體式風力機因縱搖運動造成的功率變量可觀，如考慮真實風力機之控制情形，平均功率則會耗損。由Spar型浮體式風力機進行開放縱移、起伏及縱搖三自由度運動之海上運轉模擬結果為例，縱搖角度範圍為-3.59～-6.03度，且風力機在運動過程中，功率變量達+32%～-36%，平均功率減少1.39%，如考慮真實風力機之控制情形，平均功率則減少9.17%；而Semi-submersible型浮體式風力機進行開放縱移、起伏及縱搖三自由度運動之海上運轉模擬，縱搖角度範圍為-3.50～-5.04度，在運動過程中，功率變量達+6%～-10%，平均功率減少0.99%，如考慮真實風力機之控制情形，平均功率則減少2.61%。根據本研究之模擬結果建議使用Semi-submersible型之浮體平台搭配風力機，以降低實際運轉發電時平均功率之耗損。 This paper documents the numerical study of the motion of a spar type and a semi-submersible type floating wind turbine under the coupling of aerodynamic and hydrodynamic loads (under coupled aerodynamic and hydrodynamic loads), We use a computational fluid dynamics package and solve the flow field using a Reynolds-averaged Navier-Stokes equations (RANS) solver with a proper turbulent model and also use java code to compute the mooring line force. The NREL 5MW turbine was chosen as our target wind turbine. For the onshore simulation case, the result was (results were) verified with NREL simulation results, with errors less than 8%, For the offshore simulation case, the wind turbine is undergoing pitch motion or surge, heave and pitch motion simultaneously in regular head waves of wave height 4 m, wave period 10 s and uniform wind speed 11.4 m/s. The simulation results show that the rotor power changes dramatically because of the wind turbine's pitch motion. If we consider the real wind turbine control system situation, the average power will be reduced.In the case of the spar type floating wind turbine undergoing surge, heave and pitch motion simultaneously, the results show that the spar type floating wind turbine has a pitch angle range from -3.59 to -6.03 degrees, the rotor power change is between +32% and -36%, and the average power is reduced by 1.39%. If we consider the real wind turbine control system situation, the average power is reduced by 9.17%. In the case of a semi-submersible type floating wind turbine undergoing surge, heave and pitch motion simultaneously, the results show that the spar type floating wind turbine has a pitch angle range from -3.50 to -5.04 degrees, the rotor power change is between +6% and -10%, and the average power is reduced by 0.99%, If we consider the real wind turbine control system situation, the average power is reduced by 2.61%. According to this research, we recommend the semi-submersible floating platform in order to reduce the floating wind turbine's power loss.