Surface Roughness Effects on Suction Vortex Formation: A Laboratory Simulation

Abstract

A vortex simulator is used to study multiple vortices with particular interest on the role of surface friction in their formation. Measurements with a hot-film anemometer show that the maximum velocity in a multiple-vortex system of four is greater than that for a single vortex created with the same volume flow rate. The friction experiments indicate that over a rough surface more swirl is necessary to initiate the transition to a greater number of vortices than over a smooth surface. Thus, for a tornado on the verge of a transition to multiple vortices, translation across a smoother terrain could act as a catalyst for the process.