TITLE:
Evaluating Two-Layer Models for Velocity Profiles in Open-Channels with Submerged Vegetation
AUTHORS:
Xiaonan Tang
KEYWORDS:
Aquatic Vegetation, Velocity Profile, Vegetated Flow, Analytical Model, Rigid Vegetation, Open-Channel Flow
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.7 No.1,
January
22,
2019
ABSTRACT: For submerged vegetated flow, the velocity profile has two distinctive distributions
in the vegetation layer in the lower region and the surface layer in the
upper non-vegetated region. Based on a mixing-layer analogy, different analytical
models have been proposed for the velocity profile in the two layers.
This paper evaluates the four analytical models of Klopstra et al., Defina &
Bixio, Yang et al. and Nepf against a wide range of independent experimental
data available in the literature. To test the applicability and robust of the
models, the author used the 19 datasets with various relative depths of submergence,
different vegetation densities and bed slopes (1.8 × 10−6 - 4.0 ×
10−3). This study shows that none of the models can predict the velocity profiles
well for all datasets. The three models except Yang’s model performed
reasonably well in certain cases, but Yang’s model failed in most the cases
studied. It was also found that the Defina model is almost the same as the
Klopstra model, if the same mixing length scale of eddies (λ) is used. Finally,
close examination of the mixing length scale of eddies (λ) in the Defina model
showed that when λ/h = 1/40(H/h)1/2, this model can predict velocity profiles
well for all the datasets used.