Pattern analysis of benthic boundary layer momentum and sediment transport
A general purpose pattern recognition program is developed in order to detect, analyze, and describe the turbulent velocity signal and corresponding suspended sediment concentration profiles in the benthic boundary layer of geophysical flows. Particular attention is paid to the role of waves in these structures. The basic methods utilized in the structure of the Geophysical Pattern Recognition Program (GEOPRO) are the modified pattern recognition technique (Short-Term Temporal Average, TPAV), the Variable-Interval Time-Averaging (VITA) technique and the modified Conditional Sampling Quadrant Analysis procedure with the emphasis on the first method. Detailed time series and vertical profiles of suspended sediment concentration as well as time series of different components of velocities at 15, 60, 100 and 120 cm above the bottom obtained by a near-bottom Profiling Concentration and Velocity system (PCV), deployed in 10 meter of water depth at a site one km from the Long Island coastline are analyzed. The fractional contributions to Reynolds stress from different quadrants obtained by different pattern recognition techniques indicate high contributions from sweep (55-65%) and ejection (40-50%) type of events. The ensemble average patterns of the recognized concentration profiles show strong fluctuations during ejections and sweeps when the contribution to Reynolds stress is at its maximum. They also demonstrate extreme fluctuations at the trough of the wave pattern where the vertical acceleration of the local fluid is at its maximum positive value. A comparison of the results obtained by application of different pattern recognition techniques to the benthic boundary layer data with those of wall bounded turbulent shear flow do not reveal the same kind of patterns and intermittency in the flow field.
- OSTI ID:
- 5017361
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580500* -- Oceanography-- (1980-1989)
AQUATIC ECOSYSTEMS
AQUATIC ORGANISMS
BENTHOS
BOUNDARY LAYERS
DEPOSITION
ECOLOGICAL CONCENTRATION
ECOSYSTEMS
ENVIRONMENTAL TRANSPORT
FLUID FLOW
GEOPHYSICS
LAYERS
MASS TRANSFER
MONITORING
OCEANOGRAPHY
REYNOLDS NUMBER
SEDIMENTS
TURBULENT FLOW
VELOCITY
WAVE PROPAGATION