Estimation of the bed shear stress in vegetated and bare channels
Name
924882937-MIT.pdf
Description
Full printable version
Size
5.19 MB
Format
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Checksum (MD5)
1b996416efef251118304e2e0f768dab
Author(s)
Yang, Qingjun (Judy Qingjun)
Advisor(s)
Heidi M. Nepf.
Date Issued
2015
Publisher
Massachusetts Institute of Technology
Abstract
The shear stress at the bed of a channel influences important benthic processes such as sediment transport. Several methods exist to estimate the bed shear stress in bare channels without vegetation, but most of these are not appropriate for vegetated channels due to the impact of vegetation on the velocity profile and turbulence production. This study proposes a new model to estimate the bed shear stress in both vegetated and bare channels with smooth beds. The model, which is supported by measurements, indicates that for both bare and vegetated channels with smooth beds, within a viscous sub-layer at the bed, the viscous stress decreases linearly with increasing distance from the bed, resulting in a parabolic velocity profile at the bed. For bare channels, the model describes the velocity profile in the overlap region of the Law of the Wall. For emergent canopies of sufficient density (frontal area per unit canopy volume a >/= 4.3m⁻¹ ), the thickness of the linear-stress layer is set by the stem diameter, leading to a simple estimate for bed shear stress.
Description
Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-77).
Subjects
Civil and Environmental Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
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