A Steady-State Model of Wind-Blown Sand Transport

A model for steady-state eolian saltation is presented in which computation of sand grain trajectories in the wind and of the wind velocity profile modified by saltating grain drag forces is combined with experimental data on grain-bed collisions in an iterative simulation scheme which resembles the time-development of natural saltation. Qualitative features of eolian saltation are reproduced in the simulations, including a height in the saltating layer at which the wind velocity remains roughly constant with changing free-stream friction velocity and an approximate separation of the saltating population into successively hopping grains and reptating or creeping grains. The numerical solutions give rise to more general arguments in support of the conclusions that fluid entrainment of grains is unimportant in steady-state saltation, that the mass flux profile obeys roughly an inverse power law dependence on height, and that the vertically integrated mass flux dependence on the free-stream friction velocity need not have a simple form.