Deagglomeration of fine granular materials under low-frequency vertical harmonic vibration

Abstract Resonance Acoustic Mixing® (RAM) technology applies an external low-frequency vertical harmonic vibration to mix and deagglomerate fine and ultrafine granular materials. However, although this system is used for various applications, its mechanism is yet not well understood. To address this gap in the knowledge, in this study, a continuum model of powder in a low-frequency vertical harmonic vibration container was established, and spectral proper orthogonal decomposition was used to analyse the slip velocity. The mechanism of fine particle deagglomeration with vertical harmonic vibration is proposed. The slip velocity at the interface between the particles and air has a significant periodic character and produces a persistent drag force on the particles. As the vibrational excitation frequency increases, the bandwidth of the slip velocity becomes narrower and the peak frequency becomes equal to the vibrational frequency. The drag force produced by the periodic slip velocity is the main contribution to the deagglomeration force, which needs to overcome aggregation forces (e.g., van der Waals force). The strength of the deagglomeration force determines the overall deagglomeration performance and the particle size distribution of the agglomerates.