Physical Simulation of Real Tornadoes

Abstract

Laboratory simulations of tornado-like vortices have the advantage of controlled conditions and repeatability. Previously these experiments have been conducted in Tornado Vortex Chambers (TVC). These TVC’s had the advantage of independently controlling the radial/axial flow rate and the tangential components using a fan at the top and a swirling device at the bottom. Because of the swirling device, the flow region of interest is optically inaccessible. The Wind Engineering, Energy and Environment (WindEEE) Dome at Western is a unique large, 3D wind testing chamber, of 25 meters inner diameter and 40 meters outer diameter (including the return circuit). By using a system of 100 dynamic fans on the peripheral walls coupled with 6 larger fans at the ceiling level, WindEEE can produce any type of wind systems including 4 meters in diameter translating tornadoes and downbursts as well as a variety of dynamically shear flows. Flow visualizations and surface pressure measurements demonstrate the variation of the tornado flow field with Swirl ratio which compares very well with the former TVC well controlled experiments. Full scale Doppler radar data and WindEEE PIV measurements are shown to match for a range of Fujita Scales (Fig. 1). Based on this matching, scaling relations between the laboratory (WindEEE Dome) tornadoes and real tornadoes are for the first time drawn.