Swirl Condition in Low-Pressure Vortices

A numerical method of extraction of the axis of tubular vortices in turbulent flows, which was previously proposed by Miura and Kida [J. Phys. Soc. Jpn. 66 (1997)], is improved by imposing a swirl condition. This condition guarantees the extraction of low-pressure vortices with swirling motion as well as the demarcation of the core regions around the central axis. The mean radius of vortex cores is found to be five to six times the Kolmogorov length in turbulence of micro-scale Reynolds number of 46.