Saltation of sand: a qualitative review with biological analogy

Abstract

SynopsisIn the last two decades both experimental and theoretical research in aeolian sediment transport has greatly enhanced our quantitative understanding of the saltation process. I emphasise the qualitative understanding of saltation that has emerged in part through development of a numerical model consisting of four subprocesses: (1) aerodynamic entrainment, (2) grain trajectories, (3) grain-bed impacts, and (4) momentum extraction from the wind. Each sub-model encapsulates the physics of the process, and is constrained, where necessary, by experimental data. When combined, the full model allows simulation of aeolian saltation from inception by aerodynamic entrainment to steady state. The results are encouraging, showing both qualitative and quantitative correspondence with wind tunnel measurements.In an attempt to further the qualitative understanding of the problem, an analogy is proposed between the saltation population and a biological population, wherein both individual and collective properties are considered. Although at present these models lack the detail to treat the true complexity of the natural world – in particular the wetness of beach sands and the potential role of beach vegetation – they serve both to develop our intuition about the natural setting, and to guide future experimental efforts.