(419d) Modelling of a Resonant Acoustic Mixer Using the Lattice Boltzmann Method with a Free Surface Coupled with the Discrete Element Method

Bladed mixers are widely used in many industrial processes that require mixing of a liquid phase and a solid phase (pharmaceutical, polymers, cement, etc.). Resonant acoustic mixing (RAM) is a non-contact mixing method that uses low frequency vibration to promote mixing and is a relatively new alternative to mix complex blends. RAM mixers are touted as being able to enhance mass transport, require a shorter time to mix, and apply less shear to the materials than bladed mixers, all valuable characteristics for mixing materials that are sensitive to shear and/or highly viscous. Nevertheless, the operation of this class of device is not well understood and little formal literature research is available. The primary purpose of this project is to develop a detailed understanding of the flow behavior inside the RAM, with particular emphasis on the mixing performance of a solid phase with a viscous liquid. Our methodology involves both experimental and computational examination of this device. First, we develop a code that mimics the RAM and captures the fluid flow using the lattice Boltzmann method (LBM) in three dimensions with a free surface. This model is coupled with the discrete element method (DEM) in order to elucidate the impact of particle loading on the operation of this mixer. Experimentally we use particle image velocimetry (PIV) to analyze the velocity field in the RAM. Mixtures of glycerin and water are used as the continuous fluid while PMMA, stainless steel, and glass particles allow us to vary a wide range of experimental conditions. All results are compared with simulation. Finally, we analyze the impact of particle size, fluid/particle material properties and device operational parameters on the mixing process and develop preliminary heuristics for the operation of RAM under these conditions.