Near-bed turbulence dissipation measurements in the inner surf and swash zone

Near‐bed turbulence dissipation rates were quantified in the swash zone and inner surf zone of a dissipative beach. The vertical structure and temporal evolution of the dissipation rate were calculated using the structure function applied to profiles of the vertical velocity collected by three profi...

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Bibliographic Details
Published in:Journal of geophysical research. Oceans 2013-12, Vol.118 (12), p.6634-6647
Main Authors: Lanckriet, Thijs, Puleo, Jack A.
Format: Article
Language:English
Subjects:
Backwash
Computational fluid dynamics
Density
Density stratification
Dissipation
Earth, ocean, space
Exact sciences and technology
External geophysics
Fluid flow
Geophysics
Marine
Meteorology
Oceanography
Physics of the oceans
Stratification
structure function
Surf
swash zone
Turbulence
turbulence dissipation
Turbulent flow
Water depth
Wave height
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Summary:Near‐bed turbulence dissipation rates were quantified in the swash zone and inner surf zone of a dissipative beach. The vertical structure and temporal evolution of the dissipation rate were calculated using the structure function applied to profiles of the vertical velocity collected by three profiling acoustic Doppler velocimeters. Dissipation rates between 6⋅10−5 m2/s3  and 8⋅10−3 m2/s3 were observed. Turbulence dissipation rates increased with diminishing water depth but showed no significant correlation to offshore wave height. Temporal phasing of strong turbulence dissipation events agreed well with image‐based observations of pixel intensity associated with wave breaking. Bore‐generated turbulence decayed rapidly following bore arrival and followed a decay rate similar to grid turbulence. The turbulence dissipation was dominated by (advected) bore‐generated turbulence during the uprush and initial stages of the backwash, and by bed‐generated turbulence during the later stages of the backwash. A scaling analysis shows that near the bed, sediment‐induced density stratification effects may have been an order of magnitude larger than turbulence dissipation. Key Points Turbulence dissipation was quantified using the structure function method Strong dissipation events corresponded with wave breaking detected by video A scaling analysis shows the importance of sediment density stratification
ISSN:2169-9275
2169-9291
DOI:10.1002/2013JC009251