This research will focus on an investigation of the dynamics resulting in the genesis and maintenance of tornadic vortices. The overarching hypothesis of the study is following: Smaller (subtornado vortex-scale) vortical structures in the vicinity of a primary tornado vortex undergo gyroscopically driven alignment, followed by a generalized merging process. This leads to a natural steepening of the vorticity gradient on the outer edge of the tornadic circulation. Ultimately, this isolates the vortex from turbulence-induced erosion processes. The isolation process then enables the tornado vortex to achieve strengths not easily simulated with traditional numerical models, even with resolution deemed sufficient to resolve that vortex.

Intellectual Merit: The processes leading to vortex isolation are not well represented in quasi-two-dimensional traditional atmospheric dynamics theory. Instead, the study adopts a new theoretical framework based on an analogy of the Navier-Stokes equation (hydrodynamics-HD) with electromagnetic (EM) theory. This framework has been growing in acceptance in the computational fluid dynamics (CFD) community, particularly over the last 15 years. One key point in this new approach exploits the analogous behavior between the alignment of magnetic domains within an external magnetic field, and vortical turbulence being driven to alignment (and merging) with the tornado vortex.

The research is on two fronts: (1) numerical modeling of the isolation process and (2) theoretical development describing three-dimensional scale interaction processes producing that isolation. A formulation of a vorticity backscatter process based on resolvable vorticity structure will be resulted. This new framework will then be built into the numerical model used to enable the simulation of a tornado without extreme resolution.

Broader Impacts The adopted methodologies embracing an EM-HD analogy will likely enhance understanding of all atmospheric vortex dynamics, including those that govern tropical cyclones. While this will result in a more robust comprehension of these complex processes, it will also introduce a simple, intuitive, overarching framework for future investigations. The two principal investigators plan to take advantage of this simplification to create new teaching tools that articulate the complexities of tornado formation and maintenance in a clear manner to the general public. Additionally, this work will serve as a catalyst for stressing the importance of a well-rounded physics background (including the fundamentals of electromagnetism), especially for those entering the fields of atmospheric science and fluid dynamics.

National Science Foundation (NSF)
Division of Atmospheric and Geospace Sciences (AGS)
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A. Gannet Hallar
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Western Illinois University
United States
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