Large eddy simulations of electrification of liquid dielectrics in channel flow

Abstract

In this paper we present a computational study of electrification of liquid dielectrics in channel flow and at moderate turbulence intensities. For purposes of computational savings this study consists of large eddy simulations, according to which the large turbulent scales are directly resolved by the computational grid while the effect of the smaller unresolved scales is suitably modeled. First we examine different subgrid-scale models for the electric charge density. Their efficacy is then assessed via comparisons with results from direct numerical simulations at low turbulence intensities. According to our comparisons and analysis, the most efficient model is the one based on the eddy diffusivity approach and the introduction of the turbulent electric Schmidt number. Subsequently, we present numerical results of electrification of benzene in channel flow and at different Reynolds numbers. Herein we discuss the various stages of the electrification process and the variation of the total charge and streaming current with the turbulence intensity. According to our findings, the increase of the turbulence intensity rises dramatically not only the amount of charge transported in the bulk of the fluid but also the rate at which this transport takes place. Finally, we present results for the statistics of the charge density, which provide additional insight about the distribution of the electric charges in the liquid.