Abstract
This chapter analyzes Reynolds number dependence of elementary vortices in turbulence. It aims to investigate the Reynolds number dependence of fine-scale coherent eddies called elementary vortices universally existing in various turbulence fields. The elementary vortices are detected in stable-stratified grid turbulence, homogeneous shear turbulence, and a nocturnal surface layer of which turbulence Reynolds number, Rλ, ranges from 19 to 2391. The conditional sampling is conducted referring to the steep change in transverse component of velocity fluctuation peculiar to the Burgers vortex. The resultant wave traces given by conditional averaging assured the existence of the elementary vortex similar to the Burgers vortex in all of the turbulence fields. The diameter of the elementary vortex is estimated to be about 10 times of the Kolmogorov scale being regardless of Rλ. The maximum azimuthal velocity normalized by the Kolmogorov velocity increased in proportion to Rλ0.28except for the data obtained in shear flow fields. Such dependence accords with the scaling law for the elementary vortex introduced by DNS studies.
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