Laboratory Experiment of Tornado Environment due to Cold Downdraft

Abstract

The present experimental study aims to examine the flow condition of tornado genesis due to the occurrence of downdraft. We made 32 cases of laboratory experiment changing velocity and temperature of downdraft, environmental wind velocity and the arrangement of downdraft area and updraft area. The results show that the tornado-like vortices form in the preferred velocity conditions but the their rotation direction is opposite to that of presumption. In the cases that the updraft locates the diagonally upstream side of environmental wind, the rotating direction of the tornado-like vortices is changed by the change in flow condition and the counter-rotating vortex pair is also observed. Such facts show that the arrangement between the updraft and downdraft is important condition as well as the flow condition.