An electrostatic dynamic model for wind-blown sand systems of dust devils or sand-dust storms was developed based on the electrochemistry of water molecular film on the surface of particles, in which water is ionized as H3O+/HO- and their concentration vary with temperature. The mobility of H3O+ from high concentration regime to low concentration regime is greater than that of HO-. The interaction of particles result in the change of particle kinetic energy and the particle surface temperature. The simulation of a three-sized particle system with diameters of 0.1, 0.2, and 0.4mm and particle numbers of 750, 100 and 50, respectively, shows that the small particles are charged negatively while the large particles are charged positively, which reasonably explains the electrostatic mechanism of dust devils and sand-dust storms. It was also found that the electrification is relevant to the humidity of granule system, which explains Guardiola's experiments. Coupled with gas-particle two-phase flow model, this electrostatic dynamic model will improve the accuracy of numerical simulation of the wind-blown sand system.
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