Wavelet analysis of pressure fluctuation in gas-solid two-phase flow in a horizontal pipe

In order to analyze the features of pressure fluctuation and to interpret particle flow pattern transitions, the experimental wall pressure fluctuations in swirling gas-solid two phase flows are analyzed by wavelet transform. From the wavelet analysis of pressure fluctuations, the unsteady characteristics of swirling gas-solid two-phase flows were revealed over a two dimensional time-frequency plane. The distribution of wavelet coefficients indicates the fluctuation of particle velocities and concentrations with time and scales. At low air velocities, a periodic oscillation appears in wavelet coefficients around 0.5 Hz, which may be interpreted as the existence of dunes along the bottom of the pipe at nearly constant intervals. The dominant frequency of the suspension flow increases along the flow direction and reaches 110 Hz in the fully developed region.