Modelling of resonant acoustic mixing of dry spherical particles

Abstract

This study documents the findings and methods of mapping the resonant acoustic mixing parameters of spherical particles in a cylindrical tube or container. The document systematically explores the approach followed in conducting this study by investigating the validity of certain mixing measurements, developing new measurement techniques, parameter reduction and parameter sensitivity studies to design an experimental approach that is finally used to validate a numerical discrete element model.

The study focused on separating key variables that influence the mixing outcome of each use case as well as establishing a better understanding of the mapped domain. All assumptions focused the attention on the key elements of the study to simplify each parameter to the most generic case. The study thus looks at the particle mixing behaviour of similar particles mixed in a cylindrical domain.

The study is supported by numerically analysing results that were captured using the Lagrangian discrete element method solver in the Star-CCM+ package. The simulations were launched embarrassingly parallel on a High-Performance Computer to map the domain in a reasonable time-frame. An experimental setup was constructed to aid the findings in analysing validating the numerical findings. This experimental setup has variable speed and amplitude settings which allows for a mixing intensity of up to 105Gs [1030m/s 2 ]. The setup is currently installed and in working order at the University of Pretoria.

All numerical parameters were set up such that they are in a way that it is physically implementable and realistic when varying the particle properties from soft to hard particles for various particle sizes, shaken using different container sizes. The result yielded some insight into which parameters played a larger role in the mixing efficiency; the key parameters included the container to particle volume ratio, mixing intensity and the container dimensions.

Each of these parameters had its role to play in determining the mixing state as is thoroughly explored in this study.