Modeling and simulation of electrification of wind-blown-sand two-phase flow

The electrification of wind-blown sand, such as dust storms and dust devils, is known as the tribo-electric effect of sand particles and the stratification of different size particles. Combined with the grain electrification model, a new numerical method of gas-solid two-phase flow is developed for the simulation of wind-blown-sand two-phase flow, which is a hybrid method of computational fluid dynamics and discrete element method (CFD-DEM). In the developed wind-blown-sand two-phase flow of horizontal wind tunnel, the simulation results indicate that large size grains become positively charged while small size grains become negatively charged, and the critical diameter of grain with electric neutrality is about 300μm. The simulated charge-to-mass ratio and electric field intensity of the wind-blown sands in the field wind tunnel approach to the measured data, showing the rationality of this numerical method. The simulation also demonstrates that there occurs the maximum of electric field intensity over the sand bed of the field wind tunnel, which is the reason why the electric grounding of the field wind tunnel is used in experiment. The coupling of grain electrification model and gas-solid two-phase flow method provides an important tool for interpreting laboratory and field observations of wind-blown sands and insights into the physical dynamics of dust storms and dust devils as well.