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Canopy-scale turbulence under oscillatory flow

The aim of this study is to understand the turbulent flow structure within diverse canopy models dominated by progressive waves. A set of experimental conditions were considered in a laboratory flume: three vegetation models (submerged rigid, submerged flexible and emergent rigid), three canopy densities (128, 640 and 1280 stems/m2) and three wave frequencies (f=0.8, 1 and 1.4Hz). The canopy morphology through both the plant flexibility and height and the canopy density were the characteristic parameters that exerted a control on wave induced turbulence within the canopy bed. In the flexible canopy model, sheltering at the bed was observed and was associated with the movement of the blades. In contrast, in the rigid canopy model larger TKE was found as compared with the case without canopy. The increase of TKE was associated with the production of the stem-wake turbulence. Sheltering in the submerged rigid canopy model was found at the lower layer for the largest canopy density and highest wave frequency because of a great loss of wave velocity, confined below the top of the canopy. Sweeps and ejections were the predominant events, enhancing the transfer of momentum at the top of the canopy. Therefore, below the top of the submerged rigid canopy was characterized by a vertical energy exchange zone. Unlike the submerged model, sheltering was always found for emergent rigid vegetation, and attributed to the inhibition of the wave energy at all depths

Pujol was supported by the research fellow ship BR08/11 of the University of Girona.We are also grateful for the support of the Ministerio de Ciencia e Innovación of the Spanish Government through grant CGL2010-17289 and to the Fundación Biodiversidad for their support through project AIN2011B

© Continental Shelf Research, 2013, vol. 66, p. 9-18

Elsevier

Author: Pujol, Dolors
Casamitjana, Xavier
Serra Putellas, Teresa
Date: 2013 September 1
Abstract: The aim of this study is to understand the turbulent flow structure within diverse canopy models dominated by progressive waves. A set of experimental conditions were considered in a laboratory flume: three vegetation models (submerged rigid, submerged flexible and emergent rigid), three canopy densities (128, 640 and 1280 stems/m2) and three wave frequencies (f=0.8, 1 and 1.4Hz). The canopy morphology through both the plant flexibility and height and the canopy density were the characteristic parameters that exerted a control on wave induced turbulence within the canopy bed. In the flexible canopy model, sheltering at the bed was observed and was associated with the movement of the blades. In contrast, in the rigid canopy model larger TKE was found as compared with the case without canopy. The increase of TKE was associated with the production of the stem-wake turbulence. Sheltering in the submerged rigid canopy model was found at the lower layer for the largest canopy density and highest wave frequency because of a great loss of wave velocity, confined below the top of the canopy. Sweeps and ejections were the predominant events, enhancing the transfer of momentum at the top of the canopy. Therefore, below the top of the submerged rigid canopy was characterized by a vertical energy exchange zone. Unlike the submerged model, sheltering was always found for emergent rigid vegetation, and attributed to the inhibition of the wave energy at all depths
Pujol was supported by the research fellow ship BR08/11 of the University of Girona.We are also grateful for the support of the Ministerio de Ciencia e Innovación of the Spanish Government through grant CGL2010-17289 and to the Fundación Biodiversidad for their support through project AIN2011B
Format: application/pdf
ISSN: 0278-4343
Document access: http://hdl.handle.net/10256/13473
Language: eng
Publisher: Elsevier
Collection: MICINN/PN 2011-2013/CGL2010-17289
Reproducció digital del document publicat a: http://dx.doi.org/10.1016/j.csr.2013.06.012
Articles publicats (D-F)
Is part of: © Continental Shelf Research, 2013, vol. 66, p. 9-18
Rights: Tots els drets reservats
Subject: Dinàmica de fluids
Fluid dynamics
Turbulència
Turbulence
Ones
Waves
Title: Canopy-scale turbulence under oscillatory flow
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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