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Postma J.V.,University of Alberta | Yee E.,Defence RandD Canada Suffield | Wilson J.D.,University of Alberta
Boundary-Layer Meteorology | Year: 2012

A theoretical requirement of the Interaction by Exchange with the Conditional Mean (IECM) micromixing model is that the mean concentration field produced by it must be consistent with the mean concentration field produced by a traditional Lagrangian stochastic (LS) marked particle model. We examine the violation of this requirement that occurs in a coupled LS-IECM model when unrealistically high particle velocities occur. No successful strategy was found to mitigate the effects of these rogue trajectories. It is our hope that this work will provide renewed impetus for investigation into rogue trajectories and methods to eliminate them from LS models. © 2012 Springer Science+Business Media B.V.

Postma J.V.,University of Alberta | Yee E.,Defence RandD Canada Suffield | Wilson J.D.,University of Alberta
Agricultural and Forest Meteorology | Year: 2012

A Lagrangian stochastic (LS) implementation of an interaction by exchange with the conditional mean (IECM) micromixing model is used to estimate concentration fluctuations in plumes dispersing from an in-canopy, localized source into a model plant canopy flow. The sensitivity of the LS-IECM model to the underlying Eulerian flow statistics is investigated by comparing model predictions from simulations driven by two interpolations of the same water-channel flow data. The two simulations showed minor differences in the predicted mean concentration but marked differences in the standard deviation, skewness and kurtosis of concentration. This is shown to be caused by differences in the turbulent kinetic energy (TKE) dissipation rates between the two interpolations and their effects on the IECM model. The LS-IECM model predictions of the first four moments of the scalar concentration field showed fair to good conformance (depending on which TKE dissipation rate is used) with experimental water-channel dispersion data. © 2012 Elsevier B.V.

Irvine S.E.,Defence RandD Canada Suffield
IEEE Geoscience and Remote Sensing Letters | Year: 2012

The experimental results of the response of a single-transmitter-single- receiver electromagnetic induction sensor to a linear conductor are reported. First, the sensor geometry is given, and a simple model is derived to predict the survey profile of the instrument as it moves over a linear conductor. Next, the experimental apparatus is described, and the acquired results are compared with those predicted by the model. As part of this analysis, various orientations of the transmitter and receiver dipoles are considered, as well as different tilt angles of the sensor head. The variation of peak signal strength with height above the linear conductor is also investigated. In all cases, excellent agreement between experiment and theory is achieved. These results demonstrate the potential for implementing simple sensors for detecting linear conductors or buried utilities and are important for verification of theoretical analyses. © 2012 IEEE.

Yee E.,Defence RandD Canada Suffield | Skvortsov A.,Defence Science and Technology Organisation, Australia
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

The downstream development of the concentration probability distribution along the mean-plume centerline of a dispersing plume in the wake of a ground-level continuous point source in a neutrally stratified wall-shear layer is studied. It is shown that the concentration distribution is well described by a family of one-parameter gamma distributions, as first suggested by Villermaux and Duplat in the context of confined mixing. A prediction of the downstream evolution of the parameter k (which specifies the gamma distribution) is obtained. This prediction includes explicitly the effects of mean shear on the mean-square concentration. © Published by the American Physical Society.

Hsieh K.-J.,University of Waterloo | Lien F.-S.,University of Waterloo | Yee E.,Defence RandD Canada Suffield
Flow, Turbulence and Combustion | Year: 2010

A hybrid Reynolds-averaged Navier-Stokes/Large-Eddy Simulation (RANS/LES) methodology has received considerable attention in recent years, especially in its application to wall-bounded flows at high-Reynolds numbers. In the conventional zonal hybrid approach, eddy-viscosity-type RANS and subgrid scale models are applied in the RANS and LES zones, respectively. In contrast, the non-zonal hybrid approach uses only a generalized turbulence model, which provides a unified simulation approach that spans the continuous spectrum of modeling/simulation schemes from RANS to LES. A particular realization of the non-zonal approach, known as partially resolved numerical simulation (PRNS), uses a generalized turbulence model obtained from a rescaling of a conventional RANS model through the introduction of a resolution control function F R, where F R is used to characterize the degree of modeling required to represent the unresolved scales of turbulent motion. A new generalized functional form for F R in PRNS is proposed in this study, and its performance is compared with unsteady RANS (URANS) and LES computations for attached and separated wall-bounded turbulent flows. It is demonstrated that PRNS behaves similarly to LES, but outperforms URANS in general. © 2009 Springer Science+Business Media B.V.

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