利用Fourier频谱分析和小波变换处理在平板边界层转捩过程中测得的速度信号 ,观察到频谱中存在低于基本扰动波频率的含能信号 ,即文中所谓的低频信号 .在进一步分析中 ,发现这种低频信号的产生可能与流动的间歇性有关 .由于流动的间歇性导致速度信号的脉动 ,数据结构产生间歇变化 ,这种信号并不一定对应于流场中的某一物理结构的真实频率 Fourier spectrum analysis and wavelet transform are used to deal with the velocity signals measured during the transition of slab boundary layer, and the energy signal which is lower than the frequency of the fundamental disturbance wave is observed in the spectrum, so-called low-frequency signal in the paper.In the further analysis, It is found that the generation of such low frequency signal may be related to the intermittency of the flow.While the flow of fluid intermittently results in the pulsation of the velocity signal, the data structure changes intermittently, which does not necessarily correspond to the trueness of a physical structure in the flow field frequency