基于波数-频率联合演变功率谱的一维空间非均匀脉动风场模拟

SIMULATION OF NONHOMOGENEOUS FLUCTUATING WIND FIELD IN ONE-DIMENSIONAL SPACE BY EVOLUTIONARY WAVENUMBER-FREQUENCY JOINT POWER SPECTRUM

  • 摘要: 在高层建筑、大跨桥梁和大型风力发电系统等大型工程中,风荷载对结构的安全性至关重要、甚至是起控制作用的要素。因此,脉动风速场的模拟具有重要意义。谱表达方法得到了广泛的应用。但经典的谱表达方法需要对互功率谱矩阵的逐个频率点进行Cholesky分解或本征正交分解(POD),当模拟的空间点数较多时,分解效率非常低下、甚至可能出现矩阵奇异而难以实现。基于波数-频率联合功率谱或联合演变谱,不需要Cholesky分解或POD,可以方便地实现均匀或非均匀脉动风场的模拟。当模拟点为等间距点时,该方法能够使用FFT技术提高模拟效率,而当模拟点为非等间距点、不能使用FFT技术时,模拟效率依然有待提高。鉴于此,该文引入“结构化”非均匀离散方法和“舍选法”思想,建议了二维波数-频率域的非均匀离散策略,显著地提高了模拟效率。以某桥塔的一维空间非均匀脉动风场的数值模拟为例,验证了该方法的有效性。

     

    Abstract: The simulation of fluctuating wind speed field is of a great significance, considering that the wind load is critical or even dominating for the safe design of large-sized engineering structures such as high-rise buildings, long-span bridges and megawatt wind turbines. The spectral representation method (SRM) is a kind of widely used simulation technique at present, which has to, however, deal with the challenge of unbearable computational efforts owing to the Cholesky decomposition or proper orthogonal decomposition (POD) at each discretized frequency with respect to the cross-power spectrum density (PSD) matrix. The wavenumber-frequency joint power spectrum and evolutionary wavenumber-frequency joint power spectrum based SRM were proposed recently, allowing an effective simulation of a homogeneous or nonhomogeneous wind field without Cholesky decomposition or POD. Further, the FFT technique can be utilized to improve the simulation efficiency when the spatial simulation points are evenly distributed. However, in the case of unevenly-distributed spatial simulation points, the FFT technique cannot be adopted. Thus, the simulation efficiency still needs to be enhanced. In order to reduce the computational costs resulted from the twofold summation over a frequency-wavenumber domain, the uneven discretization strategies, including structured method and acceptance-rejection method, are suggested in the present paper. The numerical examples of simulation in nonhomogeneous fluctuating wind speed fields in one-dimensional space for a bridge tower are performed, demonstrating the effectiveness of the proposed method.

     

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