Sediment Transport under Sheet-Flow Conditions

Asano, Toshiyuki

doi:10.1061/(asce)0733-950x(1995)121:5(239)

Cited by 51 publications

(48 citation statements)

References 9 publications

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“…[18] Hsu et al [2004] validate the model with detailed velocity and concentration profiles from laboratory experiments of Sumer et al [1996] for steady flow and Asano [1995] for oscillatory flow. In this paper, we are interested in the temporal variation of the volume sediment transport rate,…”

Section: Model Validationmentioning

confidence: 99%

Effects of wave shape on sheet flow sediment transport

2004

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[1] A two-phase model is implemented to study the effects of wave shape on the transport of coarse-grained sediment in the sheet flow regime. The model is based on balance equations for the average mass, momentum, and fluctuation energy for both the fluid and sediment phases. Model simulations indicate that the responses of the sheet flow, such as the velocity profiles, the instantaneous bed shear stress, the sediment flux, and the total amount of the mobilized sediment, cannot be fully parameterized by quasi-steady free-stream velocity and may be correlated with the magnitude of local horizontal pressure gradient (or free-stream acceleration). A net sediment flux in the direction of wave advance is obtained for both skewed and saw-tooth wave shapes typical of shoaled and breaking waves. The model further suggests that at critical values of the horizontal pressure gradient, there is a failure event within the bed that mobilizes more sediment into the mobile sheet and enhances the sediment flux. Preliminary attempts to parameterize the total bed shear stress and the total sediment flux appear promising.

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Section: Model Validationmentioning

confidence: 99%

Effects of wave shape on sheet flow sediment transport

2004

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“…As described by Asano [6] and Hoque et al [7], the sheet flow occurs under high shear stress where ripples are washed out. Since sheet flow is a grain-fluid mixture flow of high concentration, the mechanism is more complex than of the other modes of sediment transport.…”

Section: Structure Of the Model (Sediment Transport)mentioning

confidence: 89%

A sheet flow model to estimate the sediment transport rate for beaches backed by seawalls

Majd¹,

Neshaei²,

Taleghani³

2008

WIT Transactions on the Built Environment

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To consider the effect of reflective structures on coastal sediment transport and beach morphology, experiments have been performed at laboratory model scale on a partially reflective seawall located in the surf zone. The main objectives of these experiments were to measure beach profile evolution on an open beach with two different sizes of sand and to compare the results with those on a beach fronting a partially reflective seawall. The results obtained from the profile evolution measurements in front of reflective seawalls indicate that the extent to which a seawall affects the processes on the fronting beaches largely depends on its location relative to the active shore face. A seawall located well landward of the active shore face will behave in much the same way as a natural beach whereas seawalls located in the active shore face will modify the near-shore beach profile because of the effects of reflected waves. A simple sheet flow model, based on the measured probability density functions of near-bed horizontal velocities, is developed to predict the short-term response of a partially reflective structure to random wave attack. The main conceptual innovation of the model is taking the probability density functions of the velocities into account and integrating them to calculate the sediment displacements across the profile using a threshold criterion for initiation of sediment motion. The results obtained from the model and comparison with the experimental results are promising and encouraging for further developments of the preliminary model.

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“…It has been validated against a number of independent data sets. tested the sheet flow model for relatively massive particles against the data of Sumer et al (1996) for steady flows, and against intrawave sediment velocity and concentration data from Asano (1995) for oscillatory flows. Amoudry et al (2008) validated the model for sheet flow sand transport against data obtained in oscillatory water tunnels with Conductivity Concentration Meters for intrawave sediment concentration in the sheet layer (Dohmen-Janssen, 1999;O'Donoghue and Wright, 2004) and for sediment velocities and fluxes in the sheet layer (McLean et al, 2001).…”

Section: Model Descriptionmentioning

confidence: 99%

Parameterization of near-bed processes under collinear wave and current flows from a two-phase sheet flow model

Amoudry

Liu

2010

Continental Shelf Research

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Sediment transport models require appropriate representation of near-bed processes. We aim here to explore the parameterizations of bed shear stress, bed load transport rate and near-bed sediment erosion rate under the sheet flow regime. To that end, we employ a one-dimensional two-phase sheet flow model which is able to resolve the intrawave boundary layer and sediment dynamics at a length scale on the order of the sediment grain. We have conducted 79 numerical simulations to cover a range of collinear wave and current conditions and sediment diameters in the range 210 µm to 460 µm. The numerical results confirm that the intrawave bed shear stress leads the free stream velocity, and we assess an explicit expression relating the phase lead to the maximum velocity, wave period and bed roughness. The numerical sheet flow model is also used to provide estimates for the bed load transport rate and to inspect the near-bed sediment erosion. A common bed load transport rate formulation and two typical reference concentration approaches are assessed. A dependence of the bed load transport rate on the sediment grain diameter is observed and parameterized. Finally, the intrawave near-bed vertical sediment flux is further investigated and related to the time derivative of the bed shear stress.

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Sediment Transport under Sheet-Flow Conditions

Cited by 51 publications

References 9 publications

Effects of wave shape on sheet flow sediment transport

Effects of wave shape on sheet flow sediment transport

A sheet flow model to estimate the sediment transport rate for beaches backed by seawalls

Parameterization of near-bed processes under collinear wave and current flows from a two-phase sheet flow model

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