Visualization of Swirling Gas-solid Flow Pattern in a Horizontal Pipe Based on Wavelet Analysis of Pressure Signals

The wavelet transform is applied to experimental pressure fluctuations in swirling gas-particle two-phase flows in this paper, to identify and interpret flow pattern transitions in both Fourier and physical spaces. From randomlike pressure fluctuations the characteristic of swirling gas-particle twophase flows can be extracted, and the relationship between the wall pressure fluctuation and the particle flow patterns can be revealed over a two-dimensional timefrequency plane. The distribution of wavelet coefficients exhibits the variance of particle velocities and particle concentrations with time, and the evident branching structures in wavelet coefficients imply that particles have various velocities. At low air velocities, a periodic oscillation appears in wavelet coefficients around 0.5Hz, which may be interpreted by the existence of the dunes along the bottom of the pipe at nearly const intervals. The dominant frequency of the suspension flow increases along flow direction and reaches 110Hz in the fully developed region.