A Theoretical and Experimental Model for a Dust Devil

Abstract

The flow field found in a steady, axially-symmetric, strong atmospheric vortex of the dust-devil type is considered. The meridional plane containing the axis of the vortex is divided into an inviscid region where an unstratified free-vortex flow prevails, a plate boundary layer region, a corner region, and an axial boundary layer region. All these regions are strongly linked by a meridional circulation cell. Each of these regions is considered in turn and a solution to the overall flow field is found by matching the flow conditions at the interface between two adjacent regions. Using this model one can predict some of the features found in a model where the inviscid flow is stratified. Finally, an experimental demonstration is discussed in which the fluid is given an unstable temperature stratification with height and a source of angular momentum. A vortex of the dust-devil type forms under certain conditions.