Strong and weak, unsteady reconfiguration and its impact on turbulence structure within plant canopies
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Nepf_Strong and weak.pdf
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Author(s)
Pan, Ying
Chamecki, Marcelo
Nepf, Heidi
Follett, Elizabeth M.
Date Issued
October 2014
Journal
Physics of Fluids
Publisher
American Institute of Physics (AIP)
Citation
Pan, Ying, Elizabeth Follett, Marcelo Chamecki, and Heidi Nepf. “Strong and Weak, Unsteady Reconfiguration and Its Impact on Turbulence Structure Within Plant Canopies.” Phys. Fluids 26, no. 10 (October 2014): 105102. © 2014 AIP Publishing LLC
Version
Final published version
Abstract
Flexible terrestrial and aquatic plants bend in response to fluid motion and this reconfiguration mechanism reduces drag forces, which protects against uprooting or breaking under high winds and currents. The impact of reconfiguration on the flow can be described quantitatively by introducing a drag coefficient that decreases as a power-law function of velocity with a negative exponent known as the Vogel number. In this paper, two case studies are conducted to examine the connection between reconfiguration and turbulence dynamics within a canopy. First, a flume experiment was conducted with a model seagrass meadow. As the flow rate increased, both the mean and unsteady one-dimensional linear elastic reconfiguration increased. In the transition between the asymptotic regimes of negligible and strong reconfiguration, there is a regime of weak reconfiguration, in which the Vogel number achieved its peak negative value. Second, large-eddy simulation was conducted for a maize canopy, with different modes of reconfiguration characterized by increasingly negative values of the Vogel number. Even though the mean vertical momentum flux was constrained by field measurements, changing the mode of reconfiguration altered the distribution, strength, and fraction of momentum carried by strong and weak events. Despite the differences between these two studies, similar effects of the Vogel number on turbulence dynamics were demonstrated. In particular, a more negative Vogel number leads to a more positive peak of the skewness of streamwise velocity within the canopy, which indicates a preferential penetration of strong events into a vegetation canopy. We consider different reconfiguration geometry (one- and two-dimensional) and regime (negligible, weak, and strong) that can apply to a wide range of terrestrial and aquatic canopies.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1063/1.4898395
