Back to Search
Start Over
Sediment resuspension due to near-bed turbulent coherent structures in the nearshore
- Source :
- Continental Shelf Research. 194:104048
- Publication Year :
- 2020
- Publisher :
- Elsevier BV, 2020.
-
Abstract
- Laboratory and field experiments have suggested that near-bed sediment resuspension is an intermittent process influenced by turbulent coherent structures. This is in contrast to many sediment transport theories that relate sediment transport rates to mean near bed flow parameters. This study presents observations of turbulent bursting events obtained from two contrasting environments dominated by unidirectional and oscillatory flow regimes with mean currents higher than the critical value for sand transport. In agreement with previous laboratory and field experiments the data investigated in this study (both in unidirectional current and oscillatory flow environments) indicated that sediment resuspension was an event based system with sediment flux controlled by ejections and sweeps. Both the magnitude of the Reynolds stress and duration of the events contributed to sediment resuspension. Wavelet analysis confirmed that over time turbulence occurred in slowly evolving clusters that were closely followed by periods of strong resuspension near the bed, evolving from the primary leading scales at low frequencies, and decaying in time after the termination of the turbulent agitation. The results highlight the necessity of considering the instantaneous Reynolds shear stress effects in the existing sediment transport equations which are developed based on a time-averaged flow parameters and mean a critical velocity. Field observations presented in this study highlight the importance of considering turbulence events along with the concept of impulse as an essential parameter to be considered into future modelling of sediment movement under both unidirectional and oscillatory flows.
- Subjects :
- 0106 biological sciences
010504 meteorology & atmospheric sciences
Turbulence
010604 marine biology & hydrobiology
Geology
Reynolds stress
Mechanics
Aquatic Science
Impulse (physics)
Oceanography
Critical value
Critical ionization velocity
01 natural sciences
Physics::Fluid Dynamics
Boundary layer
Lagrangian coherent structures
Sediment transport
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 02784343
- Volume :
- 194
- Database :
- OpenAIRE
- Journal :
- Continental Shelf Research
- Accession number :
- edsair.doi...........8bffbacf99fa585b06bd0677afacf366