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Structure of turbulence and sediment stratification in wave-supported mud layers

Hooshmand, Abbas and Horner-Devine, Alexander R. and Lamb, Michael P. (2015) Structure of turbulence and sediment stratification in wave-supported mud layers. Journal of Geophysical Research. Oceans, 120 (4). pp. 2430-2448. ISSN 2169-9275.

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We present results from laboratory experiments in a wave flume with and without a sediment bed to investigate the turbulent structure and sediment dynamics of wave-supported mud layers. The presence of sediment on the bed significantly alters the structure of the wave boundary layer relative to that observed in the absence of sediment, increasing the TKE by more than a factor of 3 at low wave orbital velocities and suppressing it at the highest velocities. The transition between the low and high-velocity regimes occurs when ReΔ ≃ 450, where ReΔ is the Stokes Reynolds number. In the low-velocity regime (ReΔ < 450) the flow is significantly influenced by the formation of ripples, which enhances the TKE and Reynolds stress and increases the wave boundary layer thickness. In the high-velocity regime (ReΔ > 450) the ripples are significantly smaller, the near-bed sediment concentrations are significantly higher and density stratification due to sediment becomes important. In this regime the TKE and Reynolds stress are lower in the sediment bed runs than in comparable runs with no sediment. The regime transition at ReΔ = 450 appears to result from washout of the ripples and increased concentrations of fine sand suspended in the boundary layer, which increases the settling flux and the stratification near the bed. The increased stratification damps turbulence, especially near the top of the high-concentration layer, reducing the layer thickness. We anticipate that these effects will influence the transport capacity of wave-supported gravity currents on the continental shelf.

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Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2015 American Geophysical Union. Received 10 JUN 2014; Accepted 12 FEB 2015; Accepted article online 18 FEB 2015; Published online 2 APR 2015. We would like to thank Chris Chickadel, Jim Riley, JPaul Rinehimer, Charles Nittrouer, and Andrea Ogston for support and helpful discussions, Peter Rusello and Judah Goldberg from Nortek for their technical support, and Jeffrey Parsons for initiating the work more than a decade ago and for his support during the project. This research was funded by the National Science Foundation (OCE-000488762). Data from this paper are available upon request. Please contact Alexander Horner-Devine (
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Subject Keywords:wave boundary layer; fluid mud; stratified flows; sediment transport; turbulent kinetic energy; laboratory experiments
Record Number:CaltechAUTHORS:20150604-091253675
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Official Citation:Hooshmand, A., A. R. Horner-Devine, and M. P. Lamb (2015), Structure of turbulence and sediment stratification in wave-supported mud layers, J. Geophys. Res. Oceans, 120, 2430–2448, doi:10.1002/2014JC010231
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58001
Deposited By: Tony Diaz
Deposited On:04 Jun 2015 18:47
Last Modified:23 Nov 2016 00:45

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