16.8 The genesis and maintenance of a strong tornadic vortex through the process of vorticity confinement

Thursday, 20 August 2009: 12:15 PM
The Canyons (Sheraton Salt Lake City Hotel)
Gregory J. Tripoli, University of Wisconsin, Madison, WI; and M. L. Buker

It has been recently recognized that the numerical simulation of the full intensity of tornadic vortices is difficult using standard numerical model constructions. Tripoli (2005) reported a successful waterspout simulation by employing the technique of vorticity confinement (Steinhoff, 1994) within a highly constrained dynamics core model. Vorticity confinement, in its original form, describes a numerical technique that was designed to enable fluid dynamicists to overcome weaknesses of numerical models to simulate the longevity vortices such a those shed by airplane wings.

In this paper, new physical arguments , consistent with Newtonian dynamics, turbulence dynamics, classical thermodynamics and modern vortex dynamics, are presented describing why vorticity confinement works. In doing so a new VC framework is presented that is consistent with these principals, laboratory experiments and observations of tornado vortices. It is argued that the process of vorticity confinement is actually a real physical process that explains the basic dynamics of the tornadic vortex and the primary reason why tornadoes become so strong. At the presentation, the theory will be presented together with results of numerical experiments demonstrating how VC affects the evolution of an idealized supercell tornado.

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