非平稳脉动压力数据的SPWVD时频分析技术研究

对于高速风洞中进行的非定常流动脉动压力实验,由于传统的Fourier变换无法表示脉动压力频谱特性随时间的变化规律,因此必须借助时频分析工具进行数据处理。根据非定常流动脉动压力信号的特点,通过对几种时频分析方法进行理论分析与比较,确定Smooth Pseudo Wigner-Ville Distribution（SPWVD）方法是比较合适的分析工具。通过对实验数据进行处理,发现SPWVD具有较好的时频聚集性,能够有效地消除二次型分布固有的交叉项干扰;基于SPWVD的时频分析技术能够刻画出某实验舱门开闭过程中脉动压力的能量密度、瞬时功率以及能量谱密度随时间、频率的分布特性与动态变化;在流场参数发生改变时,SPWVD能够正确地反映出脉动压力特性随流动形态的变化。

Investigation on SPWVD time-frequency analysis technique for unstationary fluctuating pressure data

For fluctuating pressure experiments in unsteady flow fields which were conducted in high speed wind tunnel,the frequency spectrum characteristics of fluctuating pressure varying with time could not be obtained with the classic Fourier transform method,so a time-frequency analysis tool had to be adopted.According to the features of fluctuating pressure signals in unsteady flow fields,some time-frequency analysis methods were studied,then a conclusion was drawn that Smooth Pseudo Wigner-Ville Distribution（SPWVD） was an appropriate tool to analyze these signals.After applied to some experiment data,many merits about SPWVD were discovered.Firstly,it had a good-assembling time-frequency distribution,and would smooth the cross items from quadratic type distribution.Secondly,the dynamic varieties of energy density distribution,instantaneous power and energy spectrum density could be represented well based on SPWVD.At last,SPWVD plots could correctly show the characteristics of fluctuating pressure varying with flow parameters.