Mohammed Ali Saif W, Altimemy Muhannad, Jaber Hazim J, Ghayadh Nabeel A
University of Kufa, Faculty of Engineering, Department of Mechanical Engineering, Kufa, Najaf, Iraq.
Shatrah University, Faculty of Engineering, Department of Mechanical Engineering, Nasiriyah, Iraq.
Heliyon. 2024 Jun 3;10(11):e32340. doi: 10.1016/j.heliyon.2024.e32340. eCollection 2024 Jun 15.
Wind energy becomes one of the promised solutions as alternatives of using fossil power energy in the upcoming decades. As pressure fluctuation and flow deficit in the near wake play a crucial role in predicting the turbine performance, the novelty in the current study focuses on a three dimensional (3 D) transient numerical simulation to investigate near wake characteristics of NREL phase IV wind turbine. Pressure fluctuation spectrum and wake deficit at four sections downstream the turbine are the main parameters studied as well as the flow streams and iso-surface characteristics. The mentioned parameters are studied at four sections: (0.25 D), (0.5 D), (0.75 D), and (1 D) of turbine diameter. The obtained results are compared with corresponding data from the NREL Phase IV experiments for validation purposes. Results show that the highest-pressure fluctuation spectrum would be at the nearest wake region, and, then it decreases periodically. Hub pressure spectrum density is much lower than that density for the turbine blade. The wake deficit profile shows that the deficit is developing with time at a rate equal to (0.115 rate per sec). In addition, it was found that the wake is recovered just (1 d) of the hub diameter while the blade wake deficit becomes the dominant after (0.75 D) of turbine diameter to cover the whole wake region. It was also found that the downstream distances should be extended more to resolve the whole wake recovery. The comparison with the tests measurements shows agreement between both the numerical and experimental works such that the error doesn't pass 4.3 %.
在未来几十年里，风能成为有望替代化石能源的解决方案之一。由于近尾流中的压力波动和流量亏缺在预测涡轮机性能方面起着关键作用，当前研究的新颖之处在于进行三维（3D）瞬态数值模拟，以研究美国国家可再生能源实验室（NREL）第四阶段风力涡轮机的近尾流特性。涡轮机下游四个截面处的压力波动频谱和尾流亏缺是主要研究参数，同时还研究了气流和等值面特性。在涡轮机直径的四个截面处（0.25D、0.5D、0.75D和1D）对上述参数进行了研究。为了验证，将所得结果与NREL第四阶段实验的相应数据进行了比较。结果表明，最高压力波动频谱出现在最靠近尾流的区域，然后周期性降低。轮毂压力谱密度远低于涡轮机叶片的压力谱密度。尾流亏缺剖面表明，亏缺随时间以每秒0.115的速率发展。此外，发现尾流在轮毂直径1D处恢复，而叶片尾流亏缺在涡轮机直径0.75D后占主导地位，覆盖整个尾流区域。还发现下游距离应进一步延长以解决整个尾流恢复问题。与测试测量结果的比较表明，数值模拟和实验结果一致，误差不超过4.3%。
