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送交者: qingda123 2007年08月02日00:00:00 於 [教育學術] 發送悄悄話

Is the Kelvin Theorem Valid for High Reynolds Number Turbulence?

The Kelvin-Helmholtz theorem on conservation of circulation is supposed to hold for ideal inviscid fluids and is believed to be play a crucial role in turbulent phenomena. However, this expectation does not
take into account singularities in turbulent velocity fields at infinite Reynolds number. We present evidence from numerical simulations for the breakdown of the classical Kelvin theorem in the three dimensional
turbulent energy cascade. Although violated in individual realizations, we find that circulation is still conserved in some average sense. For comparison, we show that Kelvin’s theorem holds for individual realizations in the two-dimensional enstrophy cascade, in agreement with theory. The turbulent ‘cascade of circulations’ is shown to be a classical analogue of phase slip due to quantized vortices in superfluids, and various applications in geophysics and astrophysics are outlined.



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