Development of Dust Whirls and Similar Small-Scale Vortices*

Abstract

Dust whirls observed at the U. S. Naval Ordnance Test Station are described, and explanations are given for their behavior. It is shown that, although the conditions necessary for dust whirl formation are well-known, standard theories do not explain satisfactorily the dynamics of the vortex motion. Field observations, laboratory experiments, and theory all indicate that shearing motion is an important factor in dust whirl formation. It is suggested that the mechanism of small-scale convection currents is not so simple as usually assumed, but is related in many respects to the processes involved during the development of dust whirls.