Evaluation of a random displacement model for predicting particle escape from canopies using a simple eddy diffusivity model

Elizabeth Follett, Marcelo Chamecki, Heidi Nepf

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

There is a need for more practical tools for estimating spore escape from crop canopies, which is essential in forecasting the propagation of disease to other fields. In this paper, we evaluated whether a random displacement model (RDM) parameterized with an eddy diffusivity Kz(z) could be used to predict spore escape probability. The proposed RDM does not require detailed turbulence measurements for parameterization. Instead, it constructs profiles of velocity and eddy diffusivity from a simple set of parameters [canopy height, canopy density, vegetation length scale, and wind speed]. The RDM was validated using field measurements of spore concentration. On average, the model predictions matched the field measurements within 28% inside the canopy and 42% above it, comparable to LES results over the same canopy. Once validated, the RDM was used to explore particle escape across a range of canopy densities and particle settling velocities, in order to inform estimates of particle escape from crops of varying maturity or area density. Escape fraction as calculated by the RDM increased as canopy density decreased, as the ratio of particle settling velocity to turbulent shear velocity ratio decreased, and as the source height within the canopy increased.

Original languageEnglish (US)
Pages (from-to)40-48
Number of pages9
JournalAgricultural and Forest Meteorology
Volume224
DOIs
StatePublished - Aug 15 2016

Fingerprint

diffusivity
eddy
canopy
spore
particle settling
spores
settling velocity
crop
evaluation
particle
wind speed
shears
parameterization
wind velocity
turbulence
vegetation
prediction
crops

All Science Journal Classification (ASJC) codes

  • Forestry
  • Global and Planetary Change
  • Agronomy and Crop Science
  • Atmospheric Science

Cite this

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title = "Evaluation of a random displacement model for predicting particle escape from canopies using a simple eddy diffusivity model",
abstract = "There is a need for more practical tools for estimating spore escape from crop canopies, which is essential in forecasting the propagation of disease to other fields. In this paper, we evaluated whether a random displacement model (RDM) parameterized with an eddy diffusivity Kz(z) could be used to predict spore escape probability. The proposed RDM does not require detailed turbulence measurements for parameterization. Instead, it constructs profiles of velocity and eddy diffusivity from a simple set of parameters [canopy height, canopy density, vegetation length scale, and wind speed]. The RDM was validated using field measurements of spore concentration. On average, the model predictions matched the field measurements within 28{\%} inside the canopy and 42{\%} above it, comparable to LES results over the same canopy. Once validated, the RDM was used to explore particle escape across a range of canopy densities and particle settling velocities, in order to inform estimates of particle escape from crops of varying maturity or area density. Escape fraction as calculated by the RDM increased as canopy density decreased, as the ratio of particle settling velocity to turbulent shear velocity ratio decreased, and as the source height within the canopy increased.",
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Evaluation of a random displacement model for predicting particle escape from canopies using a simple eddy diffusivity model. / Follett, Elizabeth; Chamecki, Marcelo; Nepf, Heidi.

In: Agricultural and Forest Meteorology, Vol. 224, 15.08.2016, p. 40-48.

Research output: Contribution to journalArticle

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N2 - There is a need for more practical tools for estimating spore escape from crop canopies, which is essential in forecasting the propagation of disease to other fields. In this paper, we evaluated whether a random displacement model (RDM) parameterized with an eddy diffusivity Kz(z) could be used to predict spore escape probability. The proposed RDM does not require detailed turbulence measurements for parameterization. Instead, it constructs profiles of velocity and eddy diffusivity from a simple set of parameters [canopy height, canopy density, vegetation length scale, and wind speed]. The RDM was validated using field measurements of spore concentration. On average, the model predictions matched the field measurements within 28% inside the canopy and 42% above it, comparable to LES results over the same canopy. Once validated, the RDM was used to explore particle escape across a range of canopy densities and particle settling velocities, in order to inform estimates of particle escape from crops of varying maturity or area density. Escape fraction as calculated by the RDM increased as canopy density decreased, as the ratio of particle settling velocity to turbulent shear velocity ratio decreased, and as the source height within the canopy increased.

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