Intra-Wave Sediment Transport Modelling

Bosboom, J.; Klopman, G.

doi:10.1061/40549(276)192

Cited by 10 publications

(6 citation statements)

References 5 publications

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“…However, net transport rates under waves are about a factor 2.5 larger than in uniform horizontal oscillatory flows, probably because of the previously mentioned differences between boundary layer flows in OWTs and boundary layer flows under free‐surface gravity waves. Model calculations by Bosboom and Klopman [2000] indicate indeed that this difference may (partly) be attributed to the onshore‐directed boundary layer streaming that is present under waves and is absent in horizontal oscillatory flow. As a rough indication of the effect of a boundary layer streaming on the net transport rate, it is investigated what the effect is of a small positive (onshore) net current on the third‐power velocity moment, which is directly related to the net transport rate.…”

Section: Net Transport Ratesmentioning

confidence: 98%

Sheet flow dynamics under monochromatic nonbreaking waves

2002

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[1] For the first time, detailed measurements of sediment concentrations and grain velocities inside the sheet flow layer under prototype surface gravity waves have been carried out in combination with measurements of suspension processes above the sheet flow layer. Experiments were performed in a large-scale wave flume using natural sand. Sand transport under high waves in shallow water is mainly contained within the so-called ''sheet flow layer,'' a thin layer (10-60 grain diameters) in which the volume concentration of sand decreases by an order of magnitude from a value near 0.6 at the stationary bed. The thickness of the layer varies over a wave cycle and the maximum thickness increases with increasing peak Shields stress. The concentrations within the sheet flow layer vary approximately synchronously with the orbital velocity measured by an Acoustic Doppler Velocimeter (ADV) located 0.1 m above the bed, with typical phase lags of 0-p/5. In contrast, the suspended sediment concentrations a few centimeters and higher above the bed exhibit larger phase lags. Grain velocities were successfully measured in the middle and upper portions of the sheet flow layer around the time of their maximums. These velocities increased weakly with elevation from approximately 50% to 70% of the velocity outside the wave boundary layer. The observations are compared to previous experimental work and are found to be mainly consistent with observations in steady unidirectional flows and in oscillating water tunnels (OWTs), although differences in the suspended sediment concentration and the total sediment transport rate are apparent. Observations are also compared to two very different models: a 1DV suspension model for oscillatory flow with enhanced boundary roughness and a two-phase collisional grain flow model for steady unidirectional flow. While the suspension model describes the velocity profile fairly well and the collisional model describes the concentration profile well, neither model accurately predicts both the velocity and the concentration and therefore the sediment flux over the full vertical extent of the sheet flow.INDEX TERMS: 4546 Oceanography: Physical: Nearshore processes; 4558 Oceanography: Physical: Sediment transport; 3022 Marine Geology and Geophysics: Marine sediments-processes and transport; 3020 Marine Geology and Geophysics: Littoral processes; KEYWORDS: sediment transport; sheet flow; bed load; suspension; large wave flume; sand transport models Citation: Dohmen-Janssen, C. M., and D. M. Hanes, Sheet flow dynamics under monochromatic nonbreaking waves,

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Section: Net Transport Ratesmentioning

confidence: 98%

Sheet flow dynamics under monochromatic nonbreaking waves

2002

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“…Sand transport rates can be computed through vertical integration of the sediment fluxes. More information about model characteristics and about previous experiences with the model can be found in Uittenbogaard (2000), Bosboom and Klopman (2000), Uittenbogaard and Klopman (2001) and Hassan (2003). A description of the wave-tunnel version of the model as used in the present study is given below.…”

Section: Generalmentioning

confidence: 99%

Modelling of sand transport under wave-generated sheet flows with a RANS diffusion model

Hassan

Ribberink

2010

Coastal Engineering

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“…Here we use the point sand model (PSM) of Uittenbogaard and Klopman [60,61]. The model can in principle be used in a 'wave mode', so including the vertical orbital motion and wave-current interaction over the full water column.…”

Section: Downloaded By [University Of Chicago Library] At 14:09 19 Nomentioning

confidence: 99%

Sand motion induced by oscillatory flows: Sheet flow and vortex ripples

Ribberink¹,

Werf²,

Donoghue

et al. 2008

Journal of Turbulence

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A large series of field-scale experiments on turbulent sand-laden flows, conducted in preceding years in the LOWT and AOFT large oscillating water tunnels are reviewed and reanalysed. Using the combined experimental data sets, new insights are obtained on the detailed sand transport processes occurring in sheet-flow and ripple regime conditions. For sheet flow (i) new equations are presented relating maximum erosion depth and sheet-flow layer thickness to the maximum Shields parameter; (ii) detailed analysis of sediment flux data shows the dominance of the current-related flux in the sheet-flow layer and the different characters of the current-related flux for fine and medium sands; (iii) a RANS-diffusion type model is shown to reproduce important trends in net transport rate related to grain size, velocity and wave period and to predict the magnitude of net transport rate to within a factor 2 of measured values. For the ripple regime it is shown that (i) asymmetric waves generate negative ('offshore') streaming and the current-related suspended sediment flux associated with this streaming appears to be of the same order of magnitude as the wave-related suspended sediment flux; (ii) time-averaged near-bed transport and time-averaged suspended transport appear to be of about equal magnitude but of opposite sign, and are concentrated on the 'onshore' flank of the ripple for asymmetric wave conditions; (iii) near-bed transport along the onshore flank is generated by sand transported over the ripple crest during the 'onshore' half-cycle. Net sand transport under asymmetric waves can be 'onshore' directed or 'offshore' directed, depending on the degree of unsteadiness in the sand flux behaviour during the wave cycle. Dimensionless phase-lag parameters are presented, for sheet flow and ripples, which can discriminate between predominantly quasi-steady behaviour (resulting in 'onshore' transport) and predominantly unsteady behaviour (resulting in 'offshore transport').

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Intra-Wave Sediment Transport Modelling

Cited by 10 publications

References 5 publications

Sheet flow dynamics under monochromatic nonbreaking waves

Sheet flow dynamics under monochromatic nonbreaking waves

Modelling of sand transport under wave-generated sheet flows with a RANS diffusion model

Sand motion induced by oscillatory flows: Sheet flow and vortex ripples

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