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Author(s):
S. Kida and S. Goto
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Title:
Line Statistics: Stretching Rate of Passive Lines in Turbulence
Date of publication:
Mar. 2001
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Key words:
passive (material) lines, stretching, mixing, turbulence
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Abstract:
Passive lines in a statistically stationary isotropic incompressible turbulent flow are tracked numerically. The line length increases exponentially in time as exp[gamma t] with the stretching rate gamma=0.17 (Kolmogorov time)^-1 which is larger, by about 30%, than the value estimated before by the arithmetic mean of the contributions from many passive vector elements. The underestimation in previous studies is attributed to the negligence of non-uniform probability weight due to non-uniform line stretching. If the effects of non-uniformity are taken into account, the true stretching rate is recovered in the early stage of evolution up to several Kolmogorov times. Thereafter, however, it is overestimated owing to the continual separation of initially adjacent vector elements.
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