本文對完整的NREL 5MW型離岸風機在額定風速(11.4 m/s)和固定轉速(12.1 rpm)的條件下，使用基於旋轉座標的流固耦合數值方法，估算風機葉片變形，進行考慮葉片變形之旋轉風機的暫態氣動力特性與噪音分析。風機周圍不可壓縮流場計算，是基於求解納維爾史托克斯方程組及k-紊流模型，利用有限體積法進行控制方程式離散，暫態計算過程中採用滑動網格方式模擬風機葉片的旋轉運動，並藉由FWH模型(Ffowcs Williams Hawkings model)將風機周圍流場之速度與壓力變化轉換為聲壓變化，以計算風機葉片之噪音特性。本研究在流固耦合計算中，使用Abaqus軟體計算具複合材料特性葉片之變形，並使用STAR-CCM+ 軟體以旋轉網格方式模擬葉片之轉動模式，本研究利用Abaqus 與 STAR-CCM+ 之往復計算以獲得彈性葉片的穩定變形量。由旋轉葉片暫態模擬結果比較得知，彈性葉片的輸出功率較剛性葉片的輸出功率下降約2.35%，而由噪音頻譜分析可以得到，當偵測點位於風機後方15m處，彈性與剛性葉片產生的總噪音值變化不大，而當偵測點位於風機後方125m處時，彈性葉片所產生之總噪音值明顯地大於剛性葉片約10%。

In this study, the full-scale numerical simulations are performed at rated wind velocity (11.4 m/s) and rated rotor speed (12.1 rpm). The aerodynamic and aeroacoustic prediction of a NREL 5MW offshore wind turbine is performed via a Fluid-Structure Interaction (FSI) approach. The Navier–Stokes equations are used to describe the incompressible and viscous flow around the wind turbine. A k- model is adopted to take the turbulence effects of wind into account. This study used a finite volume method to discretize the governing equations. The FWH model is employed to convert the velocity and pressure change of the flow field into the sound pressure level to determine the noise characteristics. In the simulation, Abaqus is used to calculate the structure deformation of blades, whereas STAR-CCM+ is employed to simulate the flow field. With the calculation switching between Abaqus and STAR-CCM+, the stable position of deformed blades can be obtained. The power decreases about 2.35% for flexible blades when compared with that of rigid blades. The change of total sound level is not obvious between flexible and rigid blades when the detecting point is 15m behind the wind turbine. The total sound level of the flexible blade is about 10% higher than that of the rigid blade when the detecting point is 125m behind the wind turbine.

[1] 廖明夫、Gasch R.、Schubert M.，風力發電技術，西北工業大學出版社， 2009。
[2] Burton T., Sharpe D., Jenkins N. and Bossanyi E., Wind Energy Handbook, Wiley, 2011.
[3] 江俊明，考慮流固耦合效應之水平軸風力發電機氣動力特性數值研究，台灣科技大學機械系碩士論文，2013。
[4] Jonkman J.M., Butterfield S., Musial W., and Scott G., “Definition of a 5-MW Reference Wind Turbine for Offshore System Development,” National Renewable Energy Labortory, NREL/TP-500-38060, 2009.
[5] Jonkman J.M., Marshall L.B., “FAST user’s guide,” Technical report NREL/EL-500-38230. National Renewable Energy Laboratory, 2005.
[6] Pedersen A.S., and Steiniche C.S., “Safe Operation and Emergency Shutdown of Wind Turbines,” Aalborg University, 2012.
[7] 李文傑，運轉狀態下風力發電機之氣動力負荷數值研究，台灣科技大學機械系碩士論文，2013。
[8] 郭真祥、蔡國忠、趙修武、楊淳宇、李仲凱、李岱柏、林宇，「NREL 5MW風機於台灣彰濱外海地區極限風速下之氣動力負荷數值模擬研究」，2013年台灣風能學術研討會，基隆，2013。
[9] 郭真祥、趙修武、楊淳宇、林宇、李岱柏、李仲凱，「水平軸離岸風機緊急停機過程氣動力特性分析」，第二十六屆中國造船暨輪機工程研討會暨國科會成果發表會，基隆，2014。
[10] 林宇，水平軸離岸風機雙向流固耦合氣動力特性分析，台灣科技大學機械系碩士論文，2014。
[11] Bazilevs Y., Hsu M.C., Kiendl J., Wüchner R., and Bletzinger K. U., “3D simulation of wind turbine rotors at full scale. Part II: Fluid–structure interaction modeling with composite blades,” International Journal For Numerical Methods Fluids, vol. 65, pp.236-253, 2011.
[12] Hsu M.C., Bazilevs Y., “Fluid–structure interaction modeling of wind turbines: simulating the full machine,” Comput Mech, vol. 50, pp.821-833, 2012.

[13] “Fully Coupled Fluid-Structure Interaction Analysis of Wind Turbine Rotor Blades,” Abaqus Technology Brief, 2012.
[14] STAR-CCM+ Ver. 9.06 User`s Guide, 2014.
[15] Abaqus 6.14 User`s Manual, 2014.
[16] Tezduyar T., Aliabadi S., Behr M., Johnson A., Kalro V., and Litke M., “Flow simulation and high performance computing,” Comput Mech, vol. 18, pp.397-412, 1996.
[17] Bazilevs Y., Hsu M.C., Kiendl J., Wüchner R., and Bletzinger K.U., “3D simulation of wind turbine rotors at full scale. Part I: Geometry modeling and aerodynamics,” International Journal For Numerical Methods Fluids, vol. 65, pp.207-235, 2011.
[18] Lindenburg C., “Aeroelastic Modelling of the LMH64-5 Blade,” DOWEC Dutch Offshore Wind Energy Converter 1997–2003 Public Reports, 2002.
[19] Kooijman H.J.T., Lindenburg, C., Winkelaar D., and van der Hooft E.L., “DOWEC 6 MW Pre-Design: Aero-elastic modeling of the DOWEC 6 MW pre-design in PHATAS,” DOWEC Dutch Offshore Wind Energy Converter 1997–2003 Public Reports, 2003.
[20] Demirdžić I., and Perić M., “Space conservation law in finite volume calculations of fluid flow,” International Journal for Numerical Methods in Fluids, vol. 8, issue 9, pp.1037-1050, 1988
[21] Robert E., Thierry G. and Herbin R., “Finite Volume Method,” Handbooks of Numerical Analysis, vol.7, pp.713-1020, 2006.
[22] Wilcox, D.C., Turbulence Modeling for CFD, 2nd edition, DCW Industries, Inc. 1998.
[23] Menter F.R., “Two-equation eddy-viscosity turbulence modeling for engineering applications,” AIAA Journal, vol. 32, pp.1598-1605, 1994.
[24] Wanger S., BareiB R., and Guidati G., Wind Turbine Noise, 1996.
[25] Ferziger, J.H. and Perić M., Computational Methods for Fluid Dynamics, 3rd rev. ed., Springer-Verlag, Berlin, 2002.
[26] Patankar, S.V. and Spalding, D.B., “A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flows,” International Journal of Heat and Mass Transfer, vol. 15, pp.1787-1806, 1972.
[27] Hibbeler R.C., Mechanics of Materials, 8th ed., Prentice Hall, 2012.

[28] Richardson L.F., “The Approximate Arithmetical Solution by Finite Differences of Physical Problems Involving Differential Equations, with an Application to the Stresses in a Masonry Dam,” Philosophical Transactions of the Royal Society of London. Series A, vol. 210, pp.307-357, 1910.
[29] Politis E.S. and Chaviaropoulos P.K., Micrositing and classification of wind turbines in complex terrain, Wind Energy Section Centre of Renewable Energy Sources, 2008.