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Formation of a sandy near-bed transport layer from a fine-grained bed under oscillatory flow

Liang, Hanzhuang and Lamb, Michael P. and Parsons, Jeffrey D. (2007) Formation of a sandy near-bed transport layer from a fine-grained bed under oscillatory flow. Journal of Geophysical Research C, 112 (C2). pp. 1-14. ISSN 0148-0227. doi:10.1029/2006JC003635. https://resolver.caltech.edu/CaltechAUTHORS:LIAjgrc07

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Abstract

Bed surface coarsening was found to be an important effect for the formation of ripples and the dynamics of the boundary layer above a predominantly silt-sized sediment bed (median particle size equal to 26 μm; ~20% fine sand, 70% silt, 10% clay) under oscillatory flow (with orbital velocities of 0.32-0.52 m/s) in a laboratory wave duct. Following bed liquefaction, substantial winnowing of the bed surface occurred due to entrainment of finer material into suspension. Bed surface coarsening was quantified with micro-scale visualization using a CCD (charged-coupled device) camera. Under most wave orbital velocities investigated, the coarse surface particles were mobilized as a near- bed transport layer approximately 4 grain-diameters thick. The transport of these coarse sediments ultimately produced suborbital or anorbital ripples on the bed, except for the highest orbital velocities considered where the bed was planar. Micro-scale visualizations were used to construct a maximum (particle) velocity profile extending through the near-bed transport layers using particle-streak velocimetry (PSV). These profiles had a distinctive kink in log linear space at the height of the transport layer, suggesting that the near-bed sediment transport reduced skin friction and contributed to the boundary roughness through extraction of momentum.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2006JC003635DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/2006JC003635/abstractPublisherArticle
ORCID:
AuthorORCID
Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2007 by the American Geophysical Union. Received 13 April 2006; revised 13 September 2006; accepted 4 October 2006; published 6 February 2007. Financial support for the work performed was provided by grants from ONR (N00014-03-10138), NSF (EAR-0309887), and the American Chemical Society Petroleum Research Fund. The authors wish to thank T. Maxworthy and A. M. Fincham for lending us the optical system.
Funders:
Funding AgencyGrant Number
Office of Naval Research (ONR)N00014-03-10138
NSFEAR-0309887
American Chemical Society Petroleum Research FundUNSPECIFIED
Subject Keywords:size 26 mum; boundary roughness; skin friction; near bed sediment transport; PSV; particle streak velocimetry; maximum particle velocity profile; anorbital bed ripples; suborbital bed ripples; near bed transport layer; wave orbital velocity; CCD camera; fine material entrainment; bed surface winnowing; bed liquefaction; laboratory wave duct; clay; fine sand; silt sized sediment bed; boundary layer dynamics; ripple formation; bed surface coarsening; oscillatory flow; fine grained bed; sandy transport layer formation
Issue or Number:C2
DOI:10.1029/2006JC003635
Record Number:CaltechAUTHORS:LIAjgrc07
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:LIAjgrc07
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13631
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:27 May 2009 21:36
Last Modified:08 Nov 2021 22:39

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