Abstract

The time-averaged flow dynamics of a suspended cylindrical canopy patch with a bulk diameter of D is investigated using large-eddy simulations (LES). The patch consists of Nc constituent solid circular cylinders of height h and diameter d, mimicking patchy vegetation suspended in deep water (H/h ≫ 1, where H is the total flow depth). After validation against published data, LES of a uniform incident flow impinging on the canopy patch was conducted to study the effects of canopy density (0.16 ≤ φ = Nc(d/D)2 ≤ 1, by varying Nc) and bulk aspect ratio (0.25 ≤ AR = h/D ≤ 1, by varying h) on the near-wake structure and adjustment of flow pathways. The relationships between patch geometry, local flow bleeding (three-dimensional redistribution of flow entering the patch) and global flow diversion (streamwise redistribution of upstream undisturbed flow) are identified. An increase in either φ or AR decreases/increases/increases bleeding velocities through the patch surface area along the streamwise/lateral/vertical directions, respectively. However, a volumetric flux budget shows that a larger AR causes a smaller proportion of the flow rate entering the patch to bleed out vertically. The global flow diversion is found to be determined by both the patch geometrical dimensions and the local bleeding which modifies the sizes of the patch-scale near wake. While loss of flow penetrating the patch increases monotonically with increasing φ, its partition into flow diversion around and beneath the patch shows a non-monotonic dependence. The spatial extents of the wake, the flow-diversion dynamics and the bulk drag coefficients of the patch jointly reveal the fundamental differences of flow responses between suspended porous patches and their solid counterparts.

Department(s)

Civil, Architectural and Environmental Engineering

Comments

Office of Naval Research, Grant N00014-16-1-3015

Keywords and Phrases

separated flows; shear layers; wakes

International Standard Serial Number (ISSN)

1469-7645; 0022-1120

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2025 Cambridge University Press, All rights reserved.

Publication Date

10 Jan 2019

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