Abstract

The role of electrostatics in sand saltation is well known (including the formation of dunes, as well as variations of sand flows in dust storms and sand clouds in aeolology). Various electrostatic phenomena can be reproduced on the sand grains in laboratory conditions using elementary experimental setups based on two electrodes and a high-speed camera. This method does not allow to influence a single sand grain electrically and to observe all the dynamic phenomena accompanying saltation in which it participates (electrostatic multistability, reversible aggregation, rotation of sand (micro)particles, etc.). We propose to use time-resolved scanning electron microscopy for this purpose, since in the column of a scanning electron microscope it is possible to program/control the potential difference/field strength by varying the accelerating voltage on the cathode. This paper contains time-resolved microimages of the dynamics of calibrated “sand models” (with measured surface charge, porosity and morphometric distributions) are shown in the series of SEM images with 2D FFT spectra and oscillograms of the model sand particle dynamics.

Keywords:Sand saltation; Sand rotation; Sand clouds; Bagnold dunes; Electrostatic multistability; Time-resolved SEM; 2D Fourier spectra; High-speed memory oscilloscopic measurements