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Bed forms created by simulated waves and currents in a large flume

Journal of Geophysical Research C: Oceans

By:
, , , , and
DOI: 10.1029/2006JC003942

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Abstract

The morphology and evolution of bed forms created by combinations of waves and currents were investigated using an oscillating plate in a 4-m-wide flume. Current speed ranged from 0 to 30 cm/s, maximum oscillatory velocity ranged from 20 to 48 cm/s, oscillation period was 8 s (except for one run with 12 s period), and the median grain size was 0.27 mm. The angle between oscillations and current was 90°, 60°, or 45°. At the end of each run the sand bed was photographed and ripple dimensions were measured. Ripple wavelength was also determined from sonar images collected throughout the runs. Increasing the ratio of current to wave (i.e., oscillatory) velocity decreased ripple height and wavelength, in part because of the increased fluid excursion during the wave period. Increasing the ratio of current to waves, or decreasing the angle between current and waves, increased the three-dimensionality of bed forms. During the runs, ripple wavelength increased by a factor of about 2. The average number of wave periods for evolution of ripple wavelength to 90% of its final value was 184 for two-dimensional ripples starting from a flat bed. Bed form orientations at the end of each run were compared to four potential controlling factors: the directions of waves, current, maximum instantaneous bed shear stress, and maximum gross bed form normal transport (MGBNT). The directions of waves and of MGBNT were equally good predictors of bed form orientations, and were significantly better than the other two factors.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Bed forms created by simulated waves and currents in a large flume
Series title:
Journal of Geophysical Research C: Oceans
DOI:
10.1029/2006JC003942
Volume
112
Issue:
C10
Year Published:
2007
Language:
English
Publisher:
Wiley
Contributing office(s):
Coastal and Marine Geology Program
Description:
C10018; 18 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research C: Oceans