Modelling Concentration Fluctuations in Plumes Dispersing in Urban Canopy Flows within a Single Particle Lagrangian Description for Turbulent and Molecular Mixing


  1. Postma, J.V.
Corporate Authors
Defence R&D Canada - Suffield, Ralston ALTA (CAN);J.V. Postma Consulting, Edmonton AB (CAN)
An interaction by exchange with the conditional mean (IECM) micromixing model is coupled to a three-dimensional single-particle Lagrangian stochastic (LS) model to estimate concentration fluctuations in plumes of a passive (i.e., non-buoyant), non-reactive (i.e., no chemistry) tracer dispersing from a variety of source configurations in four neutrally stratified flows: a horizontally-homogeneous wall shear layer flow, a horizontally-homogeneous representation of the Tombstone canopy flow, a three-dimensional inhomogeneous representation of the Tombstone canopy flow, and a three-dimensional inhomogeneous representation of the Mock Urban Setting Trials (MUST) canopy flow. The IECM micromixing model incorporates the combined effects of turbulent and molecular mixing on particle concentration. This allows the numerical estimation of all moments of the scalar concentration field, which is a significant advance over traditional LS models given that concentration fluctuations are a ubiquitous feature of a dispersing plume. The single-particle implementation of the LS-IECM model is based upon a previously reported implementation that used simultaneously computed particle trajectories to estimate the conditional mean concentration field [Cassiani, M. A., Franzese, P. A. and Giostra, U. A.: 2005, A PDF micromixing model of dispersion for atmospheric flow. Part I: development of model, application to homogeneous turbulence and to a neutral boundary layer, Atmospheric Environment 39, 145
Report Number
DRDC-SUFFIELD-CR-2010-021 — Contractor Report (Final Report)
Date of publication
01 Nov 2009
Number of Pages
Electronic Document(PDF)

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