Passive scalar conditional statistics in a model of random advection
作者:
Emily S. C. Ching,
Y. K. Tsang,
期刊:
Physics of Fluids
(AIP Available online 1997)
卷期:
Volume 9,
issue 5
页码: 1353-1361
ISSN:1070-6631
年代: 1997
DOI:10.1063/1.869249
出版商: AIP
数据来源: AIP
摘要:
We study numerically a model of random advection of a passive scalar by an incompressible velocity field of different prescribed statistics. Our focus is on the conditional statistics of the passive scalar and specifically on two conditional averages: the averages of the time derivative squared and the second time derivative of the scalar when its fluctuation is at a given value. We find that these two conditional averages can be quite well approximated by polynomials whose coefficients can be expressed in terms of scalar moments and correlations of the scalar with its time derivatives. With the fitted polynomials for the conditional averages, analytical forms for the probability density function (pdf) of the scalar are obtained. The variation of the coefficients with the parameters of the model result in a change in the pdf. Three different kinds of velocity statistics, (i) Gaussian, (ii) exponential, and (iii) triangular, are studied, and the same qualitative results are found demonstrating that the one-point statistics of the velocity field do not affect the statistical properties of the passive scalar. ©1997 American Institute of Physics.
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