Fourier and Wavelet Analysis of Pressure Fluctuations in Gas-Non-Newtonian Liquid Two-Phase Flows in a Microchannel

The purpose of this study was to analyze the characteristics of gas-non-Newtonian liquid flow patterns in microchannels using signal processing techniques including power spectral density (PSD) and discrete wavelet transform (DWT) analyses. Square microchannels measuring 0.8 × 0.8 mm were used in this study. Water, 0.1 percent by weight (wt%) xanthan gum (XG) aqueous solution, and 0.2 wt% XG were employed as the working liquids, while nitrogen gas was used as the working gas. The superficial velocities of the liquid and gas were varied between 0.05 and 1 m/s and 0.26 and 7.8 m/s, respectively. The flow patterns were recorded using a high-speed camera, while the pressure drop was measured using a differential pressure transducer. The pressure gradient data were analyzed using signal processing techniques to characterize the flow patterns. Furthermore, PSD and DWT analyses were found to effectively describe the characteristics of the flow pattern.