采用基于滑移网格模型的三维非稳态CFD方法,对NREL Phase VI风力机在偏航工况下的动态失速特性进行计算,分析旋转周期内翼型攻角和升力系数的变化,并进一步分析非稳态流动对动态失速的影响.结果表明:偏航工况时,来流风的水平分量和翼型的非稳态绕流会延缓气流分离涡的形成和失速现象的发生,伴随的动态失速现象会显著增加叶片的动态负荷;越靠近叶根动态失速特征越明显,翼型承受的非稳态升力系数最大可达静态升力系数的5倍以上,升力系数迟滞环面积也更大.计算结果能够为风力机优化设计和运行提供理论指导.%One of the most severe operating conditions for a horizontal axis wind turbine rotor is the yaw misalignment,which will causes dynamic stall phenomenon by a cyclic variation of angle of attack at blade and accordingly increases the fatigue load. In order to relate the yawed condition with dynamic stall characteristic,a three-dimensional and time-accurate Computational Fluid Dynamics (CFD) is used for the simulations of flow-field and dynamic stall characteristic on the National Renewable Energy Laboratory (NREL) Phase VI wind turbine rotor at yaw 30 degrees. The local angle of attack and airfoil characteristics,i.e. lift coefficient Cl and drag coefficient Cd, are computed based on the simulation of the detailed flow around the rotor plane and forces acting on the blade. The results show that the horizontal component of inflow and unsteady flow around airfoil will delay the formation of flow separation vortex and the occurrence of stall. The dynamic load accompanied with dynamic stall phenomenon is significantly increased on blade,and one may observe that the unsteady lift is more than five times the two-dimensional steady lift. The hysteresis characteristic of airfoil lift and drag is more remarkable at the inboard blade sections. The derived results are helpful to develop more reliable aerodynamic models for wind turbine design codes, and also can provide theoretical guidance for the optimal design and operation of a wind turbine.
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