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A Lagrangian Stochastic Diffusion Method for Inhomogeneous Turbulence

A Lagrangian stochastic method of solving the diffusion equation for
inhomogeneous turbulence is presented in this paper. This numerical method uses (1) a first-order approximation for the spatial variation of the eddy diffusivity and (2) the corresponding first three particle position moments, to define a non-Gaussian particle position distribution. The method handles the case when the eddy diffusivity varies linearly to zero at a boundary. This is done by using the first few terms of the series
representation of the analytic solution for this case to construct the non-Gaussian position
distribution. Comparison of numerical simulation results to analytic solutions of the diffusion equation show that this method is accurate and significantly more efficient than
a previously used methods that assume a Gaussian particle position distribution.

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Date Of Record Release 2009-06-15 15:23:59
Description A Lagrangian stochastic method of solving the diffusion equation for
inhomogeneous turbulence is presented in this paper. This numerical method uses (1) a first-order approximation for the spatial variation of the eddy diffusivity and (2) the corresponding first three particle position moments, to define a non-Gaussian particle position distribution. The method handles the case when the eddy diffusivity varies linearly to zero at a boundary. This is done by using the first few terms of the series
representation of the analytic solution for this case to construct the non-Gaussian position
distribution. Comparison of numerical simulation results to analytic solutions of the diffusion equation show that this method is accurate and significantly more efficient than
a previously used methods that assume a Gaussian particle position distribution.
Classification
Resource Type
Format
Subject
Source National Atmospheric Release Advisory Center
Keyword Diffusion equation, Inhomogeneous turbulence, Eddy diffusivity, Non-Gaussian particle position distribution
Selector Stith
Date Of Record Creation 2009-06-15 15:15:45
Education Level
Date Last Modified 2010-04-09 17:09:51
Creator D.L. Ermak, J.S. Nasstrom
Language English
Date Record Checked: 2009-06-15 00:00:00 (W3C-DTF)

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