An Improved Model for Acoustic Particle Concentration - A Case Study in Piezo-Tubes

Acoustic concentration of target species inside fluidic media has gained attention as a pre-concentration step for improving the performance of several downstream applications. Majority of the existing literature on simulations of this phenomenon focuses upon a point particle assumption which states that the acoustic field responsible for concentration is unaffected by the particles treated as points in a liquid continuum. In reality, a non-zero volume occupied by the concentrating particles increasingly perturbs the local acoustic fields. This modifies the subsequent concentration process, thereby indicating a dynamic bi-directional coupling between the same and the driving acoustic fields. This paper demonstrates a novel finite element model that considers such a coupling for the first time. Acoustic concentration of latex beads inside a radially polarised piezoceramic tube filled with water is analysed as a proof of concept. By modelling the solid-liquid system as a mixture characterised by a particle volume fraction, and correlating the effective mixture properties with the acoustic fields, we show that the model is a substantial improvement over the point-particle approach. We conclude by discussing the further improvements possible in this model and potential applications where it can be implemented.