飛砂における砂粒の運動機構(1) ―砂粒の移動限界に関する実験―

Abstract

In studying the mechanism of sand storm, it is necessary to make clear the mechanicsof motion of sand grains by wind in relation to the mechanics of motion of sand grainsby water. As the first report, this paper deals with the initiation for movement of sandgrains by wind with the aid of detailed experiments. It was found that there is a widediflerence in the dimensionless expression between the dimensionless tractive force, so-called flow intensity and the Reynolds number of sand grain for the initiation for movementof sand grains by water and by wind. Using some kinds of grains with various specificgravities, the effect of specific gravity of grains on the initiation for movement was con-sidered in a laboratory experiment. It was found that the value of dimensionless criticaltractive force decreases with the increase of the relative density of grains to fluid if theReynolds number of grain is constant, and would approaches to a constant when therelative density becomes very large.