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| The importance of thermoconvective processes in the formation and intensity of atmospheric phenomena such as dust devils, cyclones or hurricanes is well known.
Dust devils are more likely to form in the presence of large horizontal temperature gradients, and the evolution of hurricane intensity depends, among other factors, on the heat exchange with the upper layer of the ocean under the core of the hurricane. All these atmosferic phenomena have a common vortical structure characterizes by a spiral up motion around an eye. No monotonic relationship is evident between eye diameter and intensity in tropical cyclones though the most intense ones all have small eye diameters. However, the change in the size of the eye can give useful information about the intensity trend.
In previous work we reported that under particular thermal conditions (including vertical and horizontal temperature gradients) and geometrical conditions (aspect ratio) numerical vortices can be generated by a convective instability in a Rayleigh-B\'enard problem in a cylindrical annulus with non-homogeneous heating from below and a lateral inflow/outflow permitted.
In this talk we study numerically the generation of stable axisymmetric vortices by ther-
moconvective mechanisms in a cylinder non-homogeneously heated from below compared to the case of an annulus.
Moreover, we show the influence of the inner radius on the stability and intensity of those vortices. Little relation is found between the intensity of the vortex and the magnitude of the inner radius. Strong stable vortices can be found for both small and large values of the inner radius. The Rankine combined vortex structure, that characterizes dust devils, is clearly observed when small values of the inner radius are considered. A radial contraction on the radius of maximum azimuthal velocity is observed when the vortex is intensified. This radius becomes nearly stationary subsequently despite the vortex keeps intensifying. These results connect with the behavior of the radius of the maximum tangential wind associated with a hurricane. Finally we will relate these results with those obtained for the case where the domain is a cylinder. |
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