大气边界层湍流相干结构的识别

首先利用数字滤波方法对淮河流域试验的大气边界层湍流观测资料进行三项分解，将大气边界层湍流的风速信号分解为近似各项同性的小尺度涡和各向异性的大尺度涡。然后再将大尺度涡信号进行离散正交小波分解，寻求相干结构的主要特征尺度。对于大气边界层湍流垂直脉动风速来说，其相干结构的主要特征尺度为16s；对径向与纬向脉动来说，其相干结构的主要特征尺度为32－64s。在此基础上，利用小波的反变换提取出相干结构的信号与非相干结构的信号，并计算两间的相关系数，最大仅有0．02。此外，对原始大气湍流观测信号不进行数字滤波，直接利用本中子波分析法提取湍流相干结构所得结果作比较研究；并探讨了采用对称或似对称离散正交小波对此研究的影响。

Identification of coherent structures of turbulence at the atmospheric surface layer

A parameter-free method based on orthonormal wavelet transforms is recommended for calculating the principal time scale of coherent structures in atmospheric boundary-layer measurements. First, the atmospheric turbulent signal is decomposed into the small scate vortex that has approximate isotropy and the large scale vortex with the digital filter. Then, the large scale vortex is used to detect colterent structures with this method. The principal time scale and profile of coherent structures for velocity components (u, v, w)above rice fields are obtained. In order to testify the validity of this method, the correlation of coherent structures and non-coherent structures are also calculated.