Development and Validation of a Lagrangian Probability Density Function Model of Horizontally-Homogeneous Turbulence Within and Above Plant Canopies |
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| Authors: | A M Reynolds |
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| Institution: | 1. Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK
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| Abstract: | Second- and third-order turbulence closure models have met with mixed success when applied to the prediction of turbulent
flows within and above plant canopies and model predictions are typically no better than those obtained using simpler two-equation
(k-e){(k-\varepsilon)} models. This is because the local gradient diffusion approximation (a crucial model requirement) cannot represent accurately
turbulent transport that is dominated by the presence of ejections and sweeps whose length scales are comparable with the
canopy height. To make progress, turbulent transport must be treated without approximation, as in Lagrangian probability density
function (PDF) models. This study is the first to develop and to validate a PDF model of horizontally-homogeneous canopy flow.
The model relies upon a prescribed length-scale that has been used elsewhere in the modelling of turbulent flows. Model predictions
compare favourably with measurements of neutrally stratified turbulent flows within and above canopies of mature corn and
forested eucalypt trees. |
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| Keywords: | |
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