A stochastic model for initial movement of sand grains by wind

摘要

A stochastic model for entrainment of sand grains by wind is presented through analysis of forces exerted on a single spherical grain, coupled with fluctuations of wind velocity and the the change in grain position on the surface. The structure of the stochastic model is consistent with experimental data in the literature. The probability of initial motion increases first, and then decreases, with grain size. It reaches a maximum at diameters of about 0-9 mm. Some sand grains are still in motion at less than the conventional threshold velocity, even at very low velocities. The probability of sand grain movement reaches unity at twice the conventional threshold velocity. Considerable discrepancies amongst conventional threshold formulae may result from the different probabilities of initial movement implied in these formulae. Copyright (C) 2008 John Wiley & Sons, Ltd.