Continuous wavelet analysis and proper orthogonal decomposition on particle dynamics in a horizontal self-exited gas-solid two-phase pipe flow

Abstract

The high-speed particle image velocimetry is applied to measure the particle velocities of a horizontal self-exited gas-solid two-phase pipe flow with soft fins at the air velocity of the minimum pressure drop. The detailed particle dynamics of using fins' cases are analyzed and compared with a conventional non-fin case. It is found that the particle accelerating process is delayed in the acceleration regime and the vertical particle velocity is decreased near the top part of fully-developed regime due to the effect of fins' oscillations. The continuous wavelet transform of axial particle fluctuation velocity suggests that the fins make the particle motions fall into a lower frequency range in the acceleration regime. In the fully-developed regime, the dominating frequencies of large-scale particle flows are decreased and the streaks appearing in the range of high frequency are weakened by using fins. The energy distributions of proper orthogonal decomposition (POD) modes indicate that the relative energy of POD mode1 is increased by using fins in both acceleration and fully-developed regimes, and the dominance is significantly enhanced by using fins in the fully-developed regime. The auto-correlation coefficients and central frequencies of POD modes exhibit that the dominating large-scale particle motion is enhanced by using fins, correspondingly, small-scale particle motion is suppressed. • The particle velocity of a horizontal self-exited gas-solid two-phase pipe flow is measured at minimum air velocity by PIV. • POD and continuous wavelet transform is adopted to analyze the particle fluctuation velocities. • The dominating frequencies of large-scale particle flows are decreased. • The streaks appears in the range of high frequency are weakened by using fins. • The dominance of POD mode 1 is significantly enhanced by using fins in the fully-developed regime.