Role of Environmental Wind Shear and Helicity in Simulated Tornadoes

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A combined use of a rotating screen at the bottom and an exhaust fan at the top of a cylindrical chamber can produce tornado-like vortices through the conservation of angular momentum. However, the existence of vertical wind shear in a thunderstorm environment can induce horizontal vorticity which in turn induces vertical vorticity when tilted by convective updrafts. By replacing the rotating screen with three tiers of plexiglass guide vanes, thereby simulating the storm-relative, vertically veering winds, the vortex chamber at the University of Oklahoma is now capable of simulating vortices by vorticity tilting instead of vorticity stretching. This project will allow extensive measurements to be made in the vortex chamber and thereby examine the role of environmental wind shear and helicity (the dot product of the vorticity vector and velocity vector) in the simulated tornadoes.