Abstract The aerodynamics of a wind turbine blade at various fixed and dynamically changing angles of attack for laminar and turbulent freestream is investigated by large-eddy simulations. The effects of freestream turbulence on the aerodynamic coefficients are analyzed for dynamic stall conditions being generated by prescribing gusts, i.e., periodically changing incoming velocity fields, onto a ClarkY airfoil at a chord based Reynolds number of R e = 150 , 000 . A synthetic turbulence generation (STG) method is extended and applied to produce the turbulent gusts in a time varying mean flow with predefined turbulence statistics, such as mean velocity, Reynolds stress tensor components, and velocity spectra. The length scales in the turbulent freestream are smaller than the blade chord length. The reduced frequency of the incoming laminar and turbulent gusts is k r e d = 0 . 2 based on the freestream velocity, chord length, and gust frequency. Dynamic stall is analyzed for an angle of attack ranging from 10 ° to 25 ° . It is shown how much the freestream turbulence level delays stall and increases lift at high angle of attack. The effect of the turbulence is most evident on the aerodynamic forces during the phase of decreasing angle of attack of the dynamic stall process, in which the reattachment of the boundary layer is enhanced by the freestream turbulence. The negative damping from the moment coefficient is also significantly reduced due to the incoming turbulence. The results show that the freestream turbulence in a turbulent flow at a turbulence level of 5% improves the aerodynamic performance of the wind turbine blade.

中文翻译：

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自由流湍流对风力机叶片动态失速的影响分析

摘要 通过大涡模拟研究了风力涡轮机叶片在各种固定攻角和动态变化攻角下的层流和湍流自由流下的空气动力学。自由流湍流对空气动力系数的影响分析了动态失速条件，该条件是由规定的阵风产生的，即周期性地改变传入速度场，以基于弦的雷诺数 Re = 150, 000 到 ClarkY 翼型。合成湍流生成 (STG) 方法被扩展并应用于在具有预定义湍流统计数据（例如平均速度、雷诺应力张量分量和速度谱）的时变平均流中产生湍流阵风。湍流自由流中的长度尺度小于叶片弦长。传入层流和湍流阵风的降低频率为 kred = 0 。2 基于自由流速度、弦长和阵风频率。针对 10° 到 25° 的攻角分析动态失速。它显示了自由流湍流水平在多大程度上延迟了失速并在大迎角增加了升力。在动态失速过程的攻角减小阶段，湍流对气动力的影响最为明显，其中自由流湍流增强了边界层的重新附着。由于进入的湍流，力矩系数的负阻尼也显着降低。结果表明，湍流水平为5%的湍流中的自由流湍流提高了风力机叶片的气动性能。