基于分形学的湍流风谱模型适用性研究

APPLICABILITY STUDY OF TURBULENT WIND SPECTRUM BASED ON FRACTAL THEORY

为避免由经验性地选择湍流风谱模型导致特定风电场风速分布规律描述不准确的问题,基于Kaimal、Von Karman、SMOOTH和NWTCUP湍流风谱模型模拟在不同地表粗糙度和湍流强度条件下所建立风场的风速分布规律,通过计盒维数分形方法计算不同风速速度曲线的分形维数,并与某风电场测风塔实测风速数据的分形维数进行比较。结果表明:风速曲线的分形维数均约为1.5,证明风速时域分布具有自相似特征。由于NWTCUP湍流风谱模型基于所选风电场的实测风速数据建立,因此NWTCUP模型在50 m高度和80 m高度处的风速分形维数与实测数据最为接近,表明分形维数可作为选择湍流风谱模型的一个重要定量参数。

Turbulent wind spectrum describes wind velocity distribution of wind field. Choosing a specific turbulent wind spectrum requires more theoretical references than experience. This paper calculates the fractal dimension of turbulent wind velocity generated by Kaimal, Von Karman, SMOOTH and NWTCUP spectrum by box counting method. The fractal dimensions are all around 1.5 which proves that wind velocity has self-similarity. NWTCUP spectrum is based on measured wind velocity data and the measured wind velocity data at height of 50 m and 80 m are also applied for fractal dimension calculation. The results show great accordance with the spectral generated one. This concludes that fractal dimension could be an important parameter and a quantify reference for wind spectrum selection.