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Aeolian Mechanics and Dune Morphodynamics |
Department of Engineering, University of Aberdeen, Aberdeen, AB9 2UE, UK
Rapid progress has been made in the last decade towards a more comprehensive model of wind blown sand transport extending and sharpening Bagnold’s classic model in significant aspects. This paper reviews the current physical model and attempts to indicate future directions of research.
The currently accepted physical model of aeolian sand transport reduces the sand transport system to four distinct sub-processes: aerodynamic entrainment; the trajectory of the wind driven sand grains; the grain/bed collision; and the modification of the wind by the driven sand. The isolation and separate treatment of these sub-processes has been an important factor in the recent rapid development of aeolian sand transport mechanics. It is, however, their interaction that produces the rich behaviour of the system. Anderson & Haff (1991) and McEwan & Willetts (1991) have synthesized the four sub-processes and constructed full saltation models which follow the system from incipience to steady-state saltation. These computer simulations provide a stern test for the physical model as the results calculated can be compared to experimental observations from field and wind tunnel. The models compare well with available data; thus we can have some confidence that the physical model is realistic. Moreover, these computer simulations have become a powerful investigative tool and have highlighted areas where our understanding is deficient.
