Abstract
Tornado visualized by funnel cloud and flying debris, is sometimes recorded as photographs and movies. Some researchers have tried to estimate the wind speed of tornado. In order to estimate the wind speed from the motion of flying debris, the characteristics of flying debris in tornado must be clarified. In this paper, the trajectories of flying debris in tornado-like flow with some different parameters, such as scale, swirl ratio and strength, are investigated by 6 DOF motion simulation of 3D flying debris. As results of this study, it is found that debris cloud is inevitably formed in tornado-like flow and this phenomenon can be explained by the equilibrium of aerodynamic forces, centrifugal force and gravity in radius-height plane. Moreover, it was clarified that the motion of flying debris in tornado is controlled by the Tachikawa number, Fluid number and Swirl ratio.
