Abstract Small-scale or scaled-down wind turbines for model experiments mostly operate in low-Reynolds-number flow. The nonlinear variations of aerodynamic coefficients with respect to the angle of attack caused by viscous effects and laminar boundary layer separation affect the wind turbine performance under these conditions. Although the vortex lattice method (VLM) is an efficient way to predict rotor performance, it tends to suffer from numerical error because nonlinear aerodynamic characteristics cannot be considered. In this study, the nonlinear vortex lattice method (NVLM) is adopted to compute the aerodynamic loads of two small-scale wind turbines. This method involves a sectional airfoil look-up table and vortex strength correction and can be applied to a wide range of operating conditions. The simulations of TU Delft and NTNU wind turbines are conducted to validate the prediction capability of numerical models by comparing predictions with the measurements. It was found that the overall results from the NVLM simulation are more accurate than the VLM results, which implies that the nonlinear aerodynamic characteristics associated with low-Reynolds-number flow should be considered to accurately assess the aerodynamic performance of small-sized wind-turbines, particularly at the low tip speed ratio at which the rotor blade may experience flow separation and dynamic stall.

中文翻译：

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低雷诺数对小型风力机气动载荷的影响

摘要 用于模型实验的小型或按比例缩小的风力涡轮机大多在低雷诺数流中运行。在这些条件下，由粘性效应和层流边界层分离引起的空气动力学系数相对于攻角的非线性变化会影响风力涡轮机的性能。尽管涡格法 (VLM) 是一种预测转子性能的有效方法，但由于无法考虑非线性气动特性，它往往会受到数值误差的影响。本研究采用非线性涡格法（NVLM）计算两台小型风力发电机的气动载荷。该方法涉及截面翼型查找表和涡流强度校正，可应用于广泛的操作条件。通过对 TU Delft 和 NTNU 风力涡轮机的模拟，将预测值与测量值进行比较，以验证数值模型的预测能力。发现 NVLM 模拟的总体结果比 VLM 结果更准确，这意味着应考虑与低雷诺数流动相关的非线性气动特性来准确评估小型风力涡轮机的气动性能，特别是在转子叶片可能经历流动分离和动态失速的低叶尖速比下。