Numerical study of non-Newtonian power-law fluids under low-frequency vertical harmonic vibration

Abstract

Resonance Acoustic MixingⓇ(RAM) technology applies an external low-frequency vertical harmonic vibration to mix ultrafine granular materials and subsequently non-Newtonian fluids. Although this system is used for various applications, its mechanism is yet not well understood, especially in the mixing of non-Newtonian fluids. To address this gap in knowledge, a phase model of the shear-thinning and shear-thickening non-Newtonian power-law fluid in a low-frequency vertical harmonic vibration container is established in this study, and the different power-law index is also considered. During the initial mixing process, there is Faraday instability at the gas–liquid interface, and Faraday waves are related to the power-law index. With the continuous input of external energy, the flow field is further destabilized, so that the uniform mixing is finally completed. In addition, the rheology of non-Newtonian fluids is consistent with the constitutive relation of power-law fluids. The dynamic viscosity of shear-thinning non-Newtonian fluid decreases rapidly with the increase of mixing time, while the shear-thickening non-Newtonian fluid decreases rapidly with the increase of mixing time. The variation of shear rate for Newtonian and non-Newtonian fluids is identical. Finally, a proper vibration parameter for the high mixing efficiency of RAM is proposed.