Periodic Trajectories in Aeolian Sand Transport

Thursday, 18 December 2014
Alexandre Valance, University of Rennes, Rennes Cedex, France and Jim T Jenkins, Cornell University, School of Civil and Environmental Engineering, Ithaca, NY, United States
Saltation is the primary mode of aeolian sand transport and refers to the hoping motion of grains over the bed [1]. We develop a simple model for steady, uniform transport in aeolian saltation over a horizontal bed that is based on the computation of periodic particle trajectories in a turbulent shearing flow [2]. The wind and the particles interact through drag, and the particles collide with the bed. We consider collisions with a rigid, bumpy bed, from which the particles rebound, and an erodible particle bed, for which a collision involves both rebound and particle ejection. The difference in the nature of the collisions results in qualitative differences in the nature of the solutions for the periodic trajectories and, in particular, to differences in the dependence of the particle flow rate on the strength of the turbulent shearing. We also discuss the pertinence of this model to describe bedload transport in water.

[1] R. A. Bagnold, « The physics of blown sand and desert dunes » , Methuen, New York (1941).
[2] J.T Jenkins and A. Valance. Periodic trajectories in Aeolian saltation transport. Physics of Fluids, 2014, 26, pp. 073301