Affordable Access

Access to the full text

The Structure of the Shear Layer in Flows over Rigid and Flexible Canopies

Authors
  • Ghisalberti, Marco1
  • Nepf, Heidi2
  • 1 University of Western Australia, School of Environmental Systems Engineering, Western Australia, Crawley, Australia , Western Australia (Australia)
  • 2 Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, Massachusetts, Cambridge, USA , Massachusetts (United States)
Type
Published Article
Journal
Environmental Fluid Mechanics
Publisher
Springer-Verlag
Publication Date
Jun 01, 2006
Volume
6
Issue
3
Pages
277–301
Identifiers
DOI: 10.1007/s10652-006-0002-4
Source
Springer Nature
Keywords
License
Yellow

Abstract

Flume experiments were conducted with rigid and flexible model vegetation to study the structure of coherent vortices (a manifestation of the Kelvin–Helmholtz instability) and vertical transport in shallow vegetated shear flows. The vortex street in a vegetated shear layer creates a pronounced oscillation in the velocity profile, with the velocity near the top of a model canopy varying by a factor of three during vortex passage. In turn, this velocity oscillation drives the coherent waving of flexible canopies. Relative to flows over rigid vegetation, the oscillation in canopy geometry has the effect of decreasing the amount of turbulent vertical momentum transport in the shear layer. Using a waving plant to determine phase in the vortex cycle, each vortex is shown to consist of a strong sweep at its front (during which the canopy is most deflected), followed by a weak ejection at its rear (when the canopy height is at a maximum). Whereas in unobstructed mixing layers the vortices span the entire layer, they encompass only 70% of the flexibly obstructed shear layer studied here.

Report this publication

Statistics

Seen <100 times