Rates of aerodynamic entrainment in a developing boundary layer

摘要: Despite its significance for inception of grain transport by wind, the initial dislodgement grains from a static surface aerodynamic forces drag and lift in absence collision has received little attention. This paper describes series wind-tunnel experiments which erosion narrow strips loose roughened flat plate exposed to range wind speeds was examined. The progressive downwind development boundary layer over provided airflow conditions permitted systematic evaluation entrainment rates arising purely forces. Use closely graded size fractions flat, single layers resting on identical, fixed support eliminated effects irregularities impacts saltation. Results show that develops with time according an inverse exponential function rate constant relates Shields dimensionless shear stress function. An empirical expression defining terms strip is derived comparisons are made between present published data. The need additional data resolve several questions raised investigation stressed. In addition, simple, objective technique accurate determination threshold any loose, granular sediment proposed.