Drag on Sparse and Rigid Emergent Canopies: Experimental and Numerical Investigation

Date

2025-11-01

Author

Haspolat, Emre
Köken, Mete

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Sediment transport and deposition processes significantly depend on the actual bed shear stresses in canopy flows, the determination of which requires a priori knowledge of the drag coefficient of vegetation arrays. The present study investigates the effect of vegetation density and a stem Reynolds number on the drag coefficient of relatively sparse emergent canopies in flows with a high stem Reynolds number by performing experimental and numerical analyses. A new type of drag plate was used in the experiments to determine the flow resistance of the vegetation array. Two empirical relationships, based on pore velocity and constricted cross-section velocity, were derived to estimate the drag coefficient of vegetation canopies across a broad range of Reynolds numbers. Further, a relation is provided, valid for a wide range of vegetation density and high stem Reynolds numbers, to predict the bed friction contribution in flow through emergent vegetation arrays. The drag coefficients based on the numerical study, where detached eddy simulation was used, are quite consistent with the experimental measurements for lower vegetation densities. Additionally, the numerical analyses provide insight into the flow physics underlying the drag mechanism of emergent vegetation arrays. Several flow characteristics inside the vegetation arrays were investigated in detail, demonstrating that turbulent kinetic energy is primarily governed by the vegetation density rather than the stem Reynolds number.

Subject Keywords

Drag coefficient, Flow resistance, Rigid emergent canopy, River dynamics, Sparse vegetation array

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105014157216&origin=inward
https://hdl.handle.net/11511/115718

Collections

Department of Civil Engineering, Article