The transport of sand by wind

The problem of the motion of an individual sand grain in wind is subjected to a physical‐mathematical analysis. An empirical equation is obtained for observed wind‐velocity profiles near the ground. The behavior of a sand grain in such a wind velocity gradient is assumed to be the result of three principal forces: the viscous drag of the air, the force of gravity, and the aerodynamic lift. Differential equations are set up on this basis. When solved by approximate methods for an average sand grain and for the profile obtained in a small wind tunnel, these equations give sand grain trajectories that agree fairly well with the trajectories observed and photographed in the wind tunnel.