Laboratory Study of Porosity Effect on Drag Induced by Circular Vegetative Patch

AbstractLaboratory experiments were conducted to directly measure the drag force induced by vegetation patches under unidirectional flow conditions. The drag force was measured with a highly responsive load cell for six patch models, of which the vegetation stems were simulated using rigid cylindric...

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Bibliographic Details
Published in:Journal of engineering mechanics 2019-07, Vol.145 (7)
Main Authors: Cheng, Nian-Sheng, Hui, Cai Ling, Wang, Xikun, Tan, Soon Keat
Format: Article
Language:English
Subjects:
Computational fluid dynamics
Computer simulation
Drag
Drag coefficients
Drag measurement
Fluid flow
Laboratories
Load cells
Porosity
Reynolds number
Rods
Technical Papers
Vegetation
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Summary:AbstractLaboratory experiments were conducted to directly measure the drag force induced by vegetation patches under unidirectional flow conditions. The drag force was measured with a highly responsive load cell for six patch models, of which the vegetation stems were simulated using rigid cylindrical rods. The measured drag coefficient varies with the Reynolds number and the number of rods included in the patch model. It generally reduces with increasing Reynolds number, and the reduction appears more significant for a patch model with fewer rods. To take into account effects of the patch porosity, this study proposed to redefine the drag coefficient and Reynolds number based on new length and velocity scales, that is, the vegetation hydraulic radius and the average velocity for the flow through the patch. This change produces a monotonic relationship between the redefined drag coefficient and redefined Reynolds number, which is generally applicable for all patch models.
ISSN:0733-9399
1943-7889
DOI:10.1061/(ASCE)EM.1943-7889.0001626