Dynamic analysis of power-law non-Newtonian fluids under low-frequency vertical harmonic vibration by dynamic mode decomposition

Abstract

Resonance acoustic mixing (RAM) technology applies an external low-frequency vertical harmonic vibration to convey and mix the non-Newtonian fluid across space. However, although this method is used for various applications, its mechanism is yet not well understood. This paper investigates the flow characteristics of the power-law non-Newtonian fluids in RAM by the phase-field numerical simulation method and proposes a mixing index to study the effect of vibration acceleration amplitude, vibration frequency, and filling rate on mixing. Dynamic mode decomposition is used to decompose the vorticity field data into spatial–temporal coherent structures to explore the dynamic mechanism of mixing under the above parameters. The results show that the increase in vibration acceleration amplitude can promote mixing uniformity and rate. The decrease in vibration frequency will increase the mixing of non-Newtonian fluids, but the effect of improvement is no longer obvious when the frequency exceeds a threshold. On the one hand, increasing the vibration acceleration amplitude and decreasing the vibration frequency and filling rate appropriately can induce the 0 Hz and half of the vibration frequency component accounting for the most energy. On the other hand, it can also increase the number of modes traversed by large-scale vortices developing into small-scale vortices. Both of them can improve the mixing rate and uniformity of non-Newtonian fluids.