Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published February 8, 2007 | Published
Journal Article Open

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

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.

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.

Attached Files

Published - LIAjgrc07.pdf

Files

LIAjgrc07.pdf
Files (796.1 kB)
Name Size Download all
md5:561ff8c2abab212b8b3f1354b2e3c96c
796.1 kB Preview Download

Additional details

Created:
August 22, 2023
Modified:
October 18, 2023