An linear correlation investigation of transient tube-wall pressure signal in the static mixer with twisted leaves

A investigation of delay time correlation characteristics of transient tube-wall pressure time series signals in a Kenics static mixer was undertaken based on wavelet transform multi-scales decomposition. The signal of pressure fluctuation are firstly decomposed into signals of different frequency bands including 0 ∼ 18.125Hz, 18.125 ∼ 36.25Hz, 36.25 ∼ 72.5Hz, 72.5 ∼ 125Hz, 125 ∼ 250Hz, 250 ∼ 500Hz, 500 ∼ 1000Hz and more than 1000Hz. The linear correlation characteristics of signal of different frequency bands are evaluated with auto-correlation function. The experimental results indicate that the signals of more than 1000 in frequency have no linear correlation for the time series signal. Under the lower dyadic scales ,j≪7, the detail signals especially d1 and d2 have larger fluctuation amplitudes which achieve 170∼180 Pa, but the amplitudes decrease as the dyadic scales increase. Under the higher dyadic scales ,j=8, the detail signals have smaller fluctuation amplitudes which achieve 20∼30 Pa.