Interplay of tribocharging and transport on particle-laden flows

It is well known that materials can develop static charges upon mechanical contact with other materials [1]. Granular materials in transport lines and fluidized beds tend to become charged due to contacts with walls and other particles [2]. The charge distribution inside these devices remains poorly understood and has gained limited attention in the literature [3,4]. The charge distribution is affected by the interplay of timescales associated with tribocharging, charge diffusion and convection. In this study, we seek a qualitative understanding of this interplay in flow of a mixture of identical particles suspended by a gas.

To address this question, we first derive a Eulerian model for charge transport [5], which can be coupled to a kinetic-theory-based model for gas-particle flow, and supplement it with a boundary condition to capture charge transfer at bounding walls. We then examine fully developed steady state solutions afforded by this model for gas-particle flow in a channel to probe the role of the relative timescales associated with tribocharging and charge diffusion.

We then couple the charge transport model with a solver for two-fluid model and simulate flow in a model gas-particle flow problem. Comparison of the results for fully-developed flow in a channel from these unsteady simulations with those obtained with the steady-state model calculations above exposes the effect of meso-scale velocity fluctuations on the interplay between tribocharging and flow.