Effect of Viscosity on Inertial Instability in a Tornado Vortex

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  • 1 Department of Atmospheric Seiences, The University of Arizona, Tucson, AZ 85721
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Abstract

A simplified analysis of the perturbation equations for nonaxisymmetric perturbations in the swirling axial flow of a tornado vortex is used to study inertial instability in the presence of viscosity. It is found that the principal effect of viscosity is to place the most unstable disturbances at finite azimuthal and axial wavenumbers, while having little effect on growth rate and structure. These results are similar to those of Emanuel for mesoscale inertial instability. The instability is not sharply peaked, but remains substantial over a large range of small azimuthal and axial wavelengths, suggesting a mechanism for turbulence.

Abstract

A simplified analysis of the perturbation equations for nonaxisymmetric perturbations in the swirling axial flow of a tornado vortex is used to study inertial instability in the presence of viscosity. It is found that the principal effect of viscosity is to place the most unstable disturbances at finite azimuthal and axial wavenumbers, while having little effect on growth rate and structure. These results are similar to those of Emanuel for mesoscale inertial instability. The instability is not sharply peaked, but remains substantial over a large range of small azimuthal and axial wavelengths, suggesting a mechanism for turbulence.

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