サーマルウインド下にある渦構造の生成、発達機構 : 熱工学,内燃機関,動力など

概要

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In the Earth's atmosphere, zonal currents with a vertical velocity gradient are induced under the action of rotation and horizontal temperature gradient. These currents satisfying the so-called "thermal wind equation" generate the cyclones and anticyclones through the baroclinic instability, and hence have serious effects on the global circulation. In this study, the generation and development mechanisms of vertical vortices associated with the cyclones and anticyclones are investigated by using direct numerical simulation of the thermal wind. By imposing the stable density stratification in the vertical direction, the effects of the stable stratification and the Reynolds number are studied in detail. As a result, we have found the distinct effects of stable stratification on the anisotropy of the flow field and the generation of the vortical structure. It is also found that the cyclone becomes dominant in comparison to the anticyclone at a relatively low Reynolds number under the weak stable stratification. At a higher Reynolds number, both cyclonic and anticyclonic vortices are enhanced by the nonlinear vortex stretching term, and hence the asymmetry between them becomes negligible. The intensive stable stratification attenuates the nonlinear vortex stretching and contributes to the occurrence of the asymmetry in the vortices even at the higher Reynolds numbers
一般社団法人日本機械学会の論文
2001-07-25