Abstract

Large-eddy simulations are performed to investigate how three-dimensional canopy geometry affects the front propagation of an incoming gravity current under a given initial forcing. A regular array of rigid square cylinders are used to represent the distributed canopy elements. It is shown that the conventional geometrical parameter of submerged canopies in constant-density flows (ah, where a is the frontal area per canopy volume and h is the canopy height) is misleading when applied to buoyancy-driven flows due to the additional complexity arising from the internal density gradients. Instead, the present study suggests a new geometrical framework consisting of a canopy density (φ) and a canopy-to-current height ratio (h), which can jointly provide an unambiguous description of the state of the current-canopy interaction. Two propagation regimes of the gravity current are identified, either along the channel bed (through-flow) or above the canopy's top boundary (over-flow). Our analysis reveals that φ and h counteract each other's effect on the transition of flow regimes. Large φ implies a strong suppression of horizontal advection within the canopy and thus promotes the through-to-over flow transition; in contrast, large h tends to promote the over-to-through flow transition due to the lack of sufficient potential energy to overcome the height jump. The end product is a complex variation pattern of a propagation regime and front velocity in the two-dimensional φ-h parameter space.

Department(s)

Civil, Architectural and Environmental Engineering

Publication Status

Available Access

Comments

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

International Standard Serial Number (ISSN)

1089-7666; 1070-6631

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2025 American Institute of Physics, All rights reserved.

Publication Date

01 Sep 2020

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