The Morphology and Dynamics of Natural and Laboratory Grain Flowsby Richard R. McDonald, UC Santa Cruz, Santa Cruz, United States,
Robert S. Anderson, UC Santa Cruz, Santa Cruz, United States,
Abstract: Artificially generated sand flows that display considerable similarity with field examples on eolian dunes allow documentation of the relationships between grainflow scales and the characteristics of the source region from which they derive. We report typical grainflow dynamics including scarp recession rates, advance rates of the toe, and surficial flow velocities within the sand avalanche. The dynamics reflects an initial tapping of sand from the source region and a subsequent translation of the granular mass. The flow itself stretches due to large downslope velocity gradients. Deduced mean grain spacing during flow is roughly 0.5 grain diameters. Velocity fluctuations within the flow, visualized with glitter traces but easily recognized as an undulatory motion of the surface, result in lateral and longitudinal velocity gradients that in turn break the flow into relatively intact patches of the order of many times the flow thickness.
Subject Headings: Soil dynamics | Grain (material) | Fluid flow | Fluid velocity | Flow duration | Flow visualization
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