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Pulse propagation in gravity currents

Allen, P. A.; Dorrell, R. M.; Harlen, O. G.; Thomas, R. E.; McCaffrey, W. D.


P. A. Allen

O. G. Harlen

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Dr Robert Thomas
Senior Research Fellow in Geomorphology and Flood Risk

W. D. McCaffrey


Real world gravity current flows rarely exist as a single discrete event, but are instead made up of multiple surges. This paper examines the propagation of surges as pulses in gravity currents. Using theoretical shallow-water modeling, we analyze the structure of pulsed flows created by the sequential release of two lock-boxes. The first release creates a gravity current, while the second creates a pulse that eventually propagates to the head of the first current. Two parameters determine the flow structure: the densimetric Froude number at the head of the current, Fr, and a dimensionless time between releases, tre. The shallow-water model enables the flow behavior to be mapped in (Fr, tre) space. Pulse speed depends on three critical characteristic curves: two that derive from the first release and correspond to a wavelike disturbance which reflects between the head of the current and the back of the lock-box and a third that originates from the second release and represents the region of the flow affected by the finite supply of source material. Pulses have non-negative acceleration until they intersect the third characteristic, after which they decelerate. Variations in pulse speed affect energy transfer and dissipation. Critically for lahars, landslides, and avalanches, pulsed flows may change from erosional to depositional, further affecting their dynamics. Gravity current hazard prediction models for such surge-prone flows may underpredict risk if they neglect internal flow dynamics.


Allen, P. A., Dorrell, R. M., Harlen, O. G., Thomas, R. E., & McCaffrey, W. D. (2020). Pulse propagation in gravity currents. Physics of Fluids, 32(1), Article 016603.

Journal Article Type Article
Acceptance Date Dec 10, 2019
Online Publication Date Jan 22, 2020
Publication Date Jan 1, 2020
Deposit Date Feb 13, 2020
Publicly Available Date Feb 14, 2020
Journal Physics of Fluids
Print ISSN 1070-6631
Electronic ISSN 1089-7666
Publisher American Institute of Physics
Peer Reviewed Peer Reviewed
Volume 32
Issue 1
Article Number 016603
Keywords Gravity currents; Equations of fluid dynamics; Fluid mechanics; Newtonian mechanics
Public URL
Publisher URL
Additional Information Received: 2019-10-04; Accepted: 2019-12-10; Published: 2020-01-22


Accepted manuscript (3.1 Mb)

Copyright Statement
© 2020, Author(s). This is an author produced version of a journal article published in Physics of Fluids. Uploaded in accordance with the publisher's self-archiving policy.

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