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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. F1, 6009, doi:10.1029/2003JF000017, 2003

Turbulent flow over three-dimensional dunes: 1. Free surface and flow response

T. B. Maddux

Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA


J. M. Nelson

Water Resources Division, U.S. Geological Survey, Denver, Colorado, USA


S. R. McLean

Department of Mechanical and Environmental Engineering, University of California, Santa Barbara, California, USA


Abstract

A series of detailed measurements were made of unidirectional turbulent open-channel flow over fixed, artificial, sinuous-crested three-dimensional (3-D) dune shapes. The response of the mean free surface was two-dimensional (2-D). Mean streamwise velocities were largest over the node of the sinuous dune crest line rather than over the maxima or minima of the crest line. Friction coefficients of the 3-D dunes were 50% higher on average in comparison to those of their 2-D counterparts when subjected to flows of similar depths and discharges. Despite the larger friction of the 3-D dunes, the turbulence generated by them was much weaker than that generated by their 2-D counterparts. The spatial structure of turbulence caused by the sinuous crest line of the 3-D dunes was correlated with the presence of secondary currents. These secondary current cells directed flow upward in the regions where the streamwise velocities were low and downward in the regions where streamwise velocities were high, suggesting that they could be responsible for a significant amount of momentum flux not being carried by the low turbulent stresses over the 3-D dunes.

Received 6 January 2003; accepted 26 August 2003; published 11 December 2003.

Index Terms: 4219 Oceanography: General: Continental shelf processes; 4235 Oceanography: General: Estuarine processes; 4546 Oceanography: Physical: Nearshore processes; 4558 Oceanography: Physical: Sediment transport; 4568 Oceanography: Physical: Turbulence, diffusion, and mixing processes.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 1043579 bytes)

Citation: Maddux, T. B., J. M. Nelson, and S. R. McLean (2003), Turbulent flow over three-dimensional dunes: 1. Free surface and flow response, J. Geophys. Res., 108(F1), 6009, doi:10.1029/2003JF000017.