A Simple Analytical Model for the Dust Devil
Abstract
A simple analytical model was developed for prescribing the velocity fields in a dust devil, a small intense vortex phenomenon common in arid regions. The propose model has a viscous inner region (boundary layer) composed of a Prandtl layer and an Ekman inflow layer and an inviscid "outer'1 region of cyclostrophic balance. Observations indicate that to a good approximation the outer flow is a Rankine combined vortex. Linearization of the equation of motion allows a solution for the radial and tangential velocities in the boundary layer and for the depth of the layer in terms of the parameters obtainable from observations: alpha(r), the inflow angle at the top of the Prandtl layer; and eta(r), a modified Ekman length determined by the outer flow. The vertical velocity field is then found by application of the continuity equation. The velocity fields are found to resemble a first-order solution by Kuo for convective atmospheric vortices and compare reasonably with the measurements of Sinclair.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1969
- Accession Number
- ADA383578
Entities
People
- Samuel E. Logan
Organizations
- University of California, Berkeley