竜巻渦など小規模渦中に発生する副次渦の実験

Abstract

The structure of the multiple vortices formed in tornado vortices is studied by a laboratoryexperiment. The number of the subsidiary vortices increases with the swirl ratio. The windfield of the multiple vortices with three subsidiary vortices is examined closely with an improvedsmoke-wire and a two component hot-wire anemometer. The core size, the maximum velocityand other properties of the subsidiary vortices are measured by the smoke-wire. The meanand the fluctuations of the velocity field is measured by the hot-wire anemometers. The spec-tral analysis of the velocity fluctuations indicates a predominant peak at the frequency associatedwith the subsidiary vortices in most of the field except for the layer near the ground. The ratioof the translation velocity of the subsidiary vortex to the mean field is about 0.9 in the upperlayers, but decreases down to about 0.7 near the ground.