Subgrid-scale modeling and large eddy simulation of electric charge transport in turbulent channel flows*

Flow electrification in wall-bounded flows occurs when electric charges are transported away from the electrical double layer, which is inevitably formed at solid-liquid interfaces, towards the bulk of the flow. It can occur during the transport and handling of low-conductivity liquids (dielectrics) that are commonly used in process industries and the energy sector, such as liquid hydrocarbons. It thus represents a major safety concern. In the past, it was suggested that turbulence plays a major role to flow electrification, which has been corroborated by recent numerical studies of ours. In this talk, and for the specific case of channel flows, we present results from direct simulations of flow electrification at weak turbulence intensities and from large-eddy simulations (LES) at higher ones. The subgrid LES model in the transport equation of the charge density is also discussed herein. We first elaborate on the various stages of flow electrification. Then, the impact of the hydrodynamic Reynolds number and the Debye length on the electrification rate and the charge-density distribution is assessed via parametric studies. Further, results for the statistical properties of the electric charge density as well as for the budget of its variance are also presented and discussed herein.