Abstract Vertical-axis wind turbines have great potential for harvesting energy with high conversion efficiency both in small-scale distributed installations and in the emerging floating offshore technology; nevertheless, their complex unsteady flow field makes design and optimization very challenging. This paper documents an extensive CFD study on a H-shaped VAWT over the entire range of operation. First, a direct 2D-3D comparison of the prediction capability of CFD models over the entire turbine operational curve is presented, highlighting the range of operation in which 3D effects become crucial and, instead, the range of TSR for which a 2D approximation is acceptable. The simulations are systematically compared to a wide and accurate experimental data set of wind-tunnel experiments in controlled conditions. The combination of CFD results with measured data allowed to assess the turbine performance and time-resolved velocity measurements in the wake. Furthermore, the paper proposes a totally novel approach in analysing the computed non-periodic unsteadiness in the wake. Finally, a tracking of the unsteady tip vortex is also proposed, with remarkable similarity to experimental results documented in the literature. This fact suggests that URANS discretization permits to approximate the dynamic and evolution of the tip vortex, at least in the near wake region.

中文翻译：

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H型垂直轴风力机全工作范围的三维非定常空气动力学

摘要 垂直轴风力发电机在小型分布式装置和新兴的海上浮动技术中具有巨大的能量收集潜力和高转换效率；然而，它们复杂的非定常流场使得设计和优化非常具有挑战性。本文记录了在整个操作范围内对 H 形 VAWT 进行的广泛 CFD 研究。首先，给出了 CFD 模型在整个涡轮机运行曲线上的预测能力的直接 2D-3D 比较，突出了 3D 效应变得至关重要的运行范围，而不是可以接受 2D 近似的 TSR 范围. 模拟结果与受控条件下风洞实验的广泛而准确的实验数据集进行了系统比较。CFD 结果与测量数据的结合允许评估尾流中的涡轮机性能和时间分辨速度测量值。此外，本文提出了一种全新的方法来分析尾流中计算出的非周期性不稳定度。最后，还提出了对不稳定尖端涡流的跟踪，与文献中记录的实验结果非常相似。这一事实表明 URANS 离散化允许近似尖端涡流的动态和演化，至少在近尾流区域是这样。与文献中记录的实验结果具有显着的相似性。这一事实表明 URANS 离散化允许近似尖端涡流的动态和演化，至少在近尾流区域是这样。与文献中记录的实验结果具有显着的相似性。这一事实表明 URANS 离散化允许近似尖端涡流的动态和演化，至少在近尾流区域是这样。