Statistics of an advected passive scalar
作者:
Yoshifumi Kimura,
Robert H. Kraichnan,
期刊:
Physics of Fluids A
(AIP Available online 1993)
卷期:
Volume 5,
issue 9
页码: 2264-2277
ISSN:0899-8213
年代: 1993
DOI:10.1063/1.858530
出版商: AIP
数据来源: AIP
摘要:
An elementary argument shows that non‐Gaussian fluctuations in the temperature at a point in space are induced by random advection of a passive temperature field that has a nonlinear mean gradient, whether or not there is molecular diffusion. This is corroborated by exact analysis for the nondiffusive case and by direct numerical simulation for diffusive cases. Eulerian mapping closure gives results close to the simulation data. Non‐Gaussian fluctuations of temperature at a point also are induced by a more subtle mechanism that requires both advection and molecular diffusion and is effective even when the statistics are strictly homogeneous. It operates through selectively strong dissipation of regions where intense temperature gradients have been induced by advective straining. This phenomenon is demonstrated by simulations and explored by means of an idealized analytical model.
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