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ISSN オンライン: 2642-0554

NONUNIFORM STRETCHED WEIGHT IN LINE STATISTICS OF TURBULENCE

Susumu Goto
Department of Mechanical Engineering, Okayama University, 3-1-1, Tsushimanaka, Okayama, 700-8530, Japan; Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531 Japan

Shigeo Kida
Department of Mechanical Engineering, Kyoto University, Yoshida-Honmachi, Sakyo, Kyoto 606-8501; Theory and Computer Simulation Center, National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, 509-5292, Japan

要約

Statistics of passive material lines in homogeneous isotropic turbulence are investigated by the use of direct numerical simulations. Passive material lines are stretched locally by the Kolmogorov-scale vortices, and their total length increases exponentially in time with the stretching rate of 0.17 (Kolmogorov time)−1 at the Taylor-micro-scale Reynolds numbers of 56 and 84. It is shown theoretically and numerically that the commonly used simple arithmetic mean of stretching rates of many infinitesimal line elements underestimates the real stretching rate of passive material lines owning to nonuniform stretching along the lines.