Summary of the Physics of Grain Movement in air

Abstract

THE movement of sand by wind is but one aspect of the wider subject of the carriage of solid particles of whatever kind by fluids in general. Great progress has been made in recent years both in our knowledge of the nature of the internal turbulent eddies within the fluid, caused by the presence of solid boundary walls, and in the effect of these eddies on the fluid flow as a whole. Much careful experimental work has also been devoted to the resistance offered by a fluid at rest to the motion through it of single particles of various shapes, sizes, and densities. But no general principles have so far been formulated whereby the precise effects which the presence of large numbers of such particles have upon the internal flow structure of the fluid surrounding them can be calculated.