林带背风面湍流谱特征的初步分析

本文应用湍流谱分析的方法研究了林带背风面湍涡运动的周期、频率和振幅等谱特征。结果表明,湍流谱密度在低频区存在较大差异;在高频区,不同树高倍数处的谱密度均服从-5/3的指数定律,满足局地各向同性的理论。结合欧拉自相关分析表明,在林缘附近形成较小尺度的湍涡,其频率较高,周期较小,而远离林带处形成较大尺度的湍涡,其频率较低,周期较大。

A PRELIMINARY SPECTRUM ANALYSIS ON TURBULENCE IN LEESIDE OF WINDBREAKS

The spectrum characteristics of turbulence such as period of fluctuation, frequncy, and amplitude of oscillation were discussed by using the method of spectral analysis of turbulence in this paper. The results show that the spectrum density in the range of low frequncy is sharply variance with the distance from the windbrcaks, but it follows the power index law of -5 / 3 and satisfies the theory of local isotropic turbulencc in the range of high frequncy. It also shows by connecting with Eulerium autocorrelation analysis that there are small scale, high frequncy and short period of turbulence near the leeside of windbreaks, but often large scale, low frcquncy and long period of turbulence far from the windbreaks.