Abstract

The propagation of full-depth lock-exchange bottom gravity currents past a submerged array of circular cylinders is investigated using laboratory experiments and large eddy simulations. Firstly, to investigate the front velocity of gravity currents across the whole range of array density (i.e. the volume fraction of solids), the array is densified from a flatbed towards a solid slab under a particular submergence ratio, where is the flow depth and is the array height. The time-averaged front velocity in the slumping phase of the gravity current is found to first decrease and then increase with increasing. Next, a new geometrical framework consisting of a streamwise array density and a spanwise array density is proposed to account for organized but non-equidistant arrays, where and are the streamwise and spanwise cylinder spacings, respectively, and is the cylinder diameter. It is argued that this two-dimensional parameter space can provide a more quantitative and unambiguous description of the current-array interaction compared with the array density given by. Both in-line and staggered arrays are investigated. Four dynamically different flow regimes are identified: (i) through-flow propagating in the array interior subject to individual cylinder wakes ( : small for in-line array and arbitrary for staggered array; : small); (ii) over-flow propagating on the top of the array subject to vertical convective instability ( : large; : large); (iii) plunging-flow climbing sparse close-to-impermeable rows of cylinders with minor streamwise intrusion ( : small; : large); and (iv) skimming-flow channelized by an in-line array into several subcurrents with strong wake sheltering ( : large; : small). The most remarkable difference between in-line and staggered arrays is the non-existence of skimming-flow in the latter due to the flow interruption by the offset rows. Our analysis reveals that as increases, the change of flow regime from through-flow towards over- or skimming-flow is responsible for increasing the gravity current front velocity.

Department(s)

Civil, Architectural and Environmental Engineering

Comments

National Science Foundation, Grant 1151838

Keywords and Phrases

geophysical and geological flows; gravity currents; topographic effects

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

25 Nov 2017

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