期刊
JOURNAL OF FLUID MECHANICS
卷 666, 期 -, 页码 573-604出版社
CAMBRIDGE UNIV PRESS
DOI: 10.1017/S0022112010004544
关键词
atmospheric flows; turbulent boundary layers; turbulent flows
资金
- ONR [N00014-08-1-0897]
Simultaneous streamwise velocity measurements across the vertical direction obtained in the atmospheric surface layer (Re-tau similar or equal to 5 x 105) under near thermally neutral conditions are used to outline and quantify interactions between the scales of turbulence, from the very-large-scale motions to the dissipative scales. Results from conditioned spectra, joint probability density functions and conditional averages show that the signature of very-large-scale oscillations can be found across the whole wall region and that these scales interact with the near-wall turbulence from the energy-containing eddies to the dissipative scales, most strongly in a layer close to the wall, z(+) less than or similar to 10(3). The scale separation achievable in the atmospheric surface layer appears to be a key difference from the low-Reynolds-number picture, in which structures attached to the wall are known to extend through the full wall-normal extent of the boundary layer. A phenomenological picture of very-large-scale motions coexisting and interacting with structures from the hairpin paradigm is provided here for the high-Reynolds-number case. In particular, it is inferred that the hairpin-packet conceptual model may not be exhaustively representative of the whole wall region, but only of a near-wall layer of z(+) = O(10(3)), where scale interactions are mostly confined.
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