A Sheetflow Transport Model for Asymmetric Oscillatory Flows Part II: Mixed Grain Size Sediments

Ahmed, Ahmed S. M.; Sato, Shinji

doi:10.1142/s0578563403000798

Cited by 18 publications

(19 citation statements)

References 7 publications

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“…Experimental studies to investigate sheet flow have been conducted primarily in oscillatory flow tunnels [Horikawa et al, 1982;Ribberink and Al-Salem, 1995;Dibajnia and Watanabe, 1998;Dohmen-Janssen et al, 2001;Ahmed and Sato, 2003;Wright, 2004a, 2004b;van der A et al, 2010;Ruessink et al, 2011;Dong et al, 2013], supplemented by wave flume studies Hanes, 2002, 2005;Chassagneux and Hurther, 2014]. A main outcome was the development of empirical formulas for the net sheet flow sediment transport aimed toward use in large-scale morphodynamic models [Drake and Calantoni, 2001;Hoefel and Elgar, 2003;Watanabe and Sato, 2004;Camenen and Larson, 2006;da Silva et al, 2006;Nielsen, 2006;Gonzalez-Rodriguez and Madsen, 2007;van der A et al, 2010.…”

Section: Introductionmentioning

confidence: 99%

A semianalytical model for sheet flow layer thickness with application to the swash zone

Lanckriet

Puleo

2015

JGR Oceans

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A new semianalytical model for the time-dependent thickness of the sheet flow layer that includes the effects of pressure gradients, bed slope, boundary layer growth, and bore turbulence is presented. The shear stress and boundary layer growth are computed using the boundary layer integral method. The model is expressed as two coupled ordinary differential equations that are solved numerically given a prescribed time series of free-stream velocity, horizontal pressure gradient and bore turbulence, which together represent the hydrodynamic forcing. The model was validated against two data sets of sheet flow layer thickness collected in oscillatory flow tunnels and one data set collected in the swash zone of a prototype-scale laboratory experiment. In the oscillatory flow tunnel data sets, sheet flow is mostly generated by shear stress, with pressure gradients providing an important secondary forcing around flow reversal. In the swash zone, pressure gradients and shear stresses alone are not sufficient to generate the large sheet flow layer thickness observed at the initial stages of uprush. Bore turbulence is most likely the dominant generation mechanism for this intense sheet flow.

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Section: Introductionmentioning

confidence: 99%

A semianalytical model for sheet flow layer thickness with application to the swash zone

Lanckriet

Puleo

2015

JGR Oceans

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“…Experiments in recirculating flow tunnels (Shook et al 1982;Sumer et al 1996;Pugh and Wilson 1999) provided additional insights into the velocity and sediment concentration profiles in the sheet flow layer and the increased bed roughness due to sheet flow. Sheet flow measurements under sinusoidal, asymmetric and irregular forcing were conducted in oscillatory flow tunnels (Horikawa et al 1982;Ribberink and Al-Salem 1995;Dibajnia and Watanabe 1998;Dohmen-Janssen et al 2001;Ahmed and Sato 2003;O'Donoghue and Wright 2004b;Ribberink et al 2008;van der A et al 2010;Capart and Fraccarollo 2011;Ruessink et al 2011;Dong et al 2013). These studies have established thresholds for the transition between the ripple regime and the sheet flow regime, and have provided the most detailed sediment concentration and velocity profiles in the sheet layer to date.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Field Study of Swash-Zone Processes. II: Sheet Flow Sediment Concentrations during Quasi-Steady Backwash

Lanckriet

Puleo

Masselink

et al. 2014

J. Waterway, Port, Coastal, Ocean Eng.

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Sheet flow sediment concentration profiles were measured in natural conditions for the first time as part of a comprehensive field study on swash-zone hydrodynamics and sediment transport. Three conductivity concentration profilers (CCPs) measured the sediment concentration profile in the sheet flow layer with a 1 mm resolution in the swash zone of a dissipative beach. This paper focuses on sheet flow during quasi-steady backwash events generated by infragravity motion when the effects of phase lags, surface-generated turbulence and accelerations are small. The sheet flow sediment concentration profile has a linear shape in the lower section of the profile and a power-law shape in the upper section, with the transition occurring at sediment volume fractions of 0.20-0.30. The shape of the concentration profile is self-similar for measured sheet flow layer thicknesses ranging from 6 mm to 18 mm. Because of the self-similarity, a single concentration profile curve can be used to describe the normalized profile for the entire range of sheet thicknesses, leading to improved estimates of the sheet flow layer thickness in a simple analytical model. The sheet flow layer thickness and sheet load, the sediment mass mobilized in the sheet flow layer, are wellcorrelated with the hydrodynamic forcing represented by the mobility number (r 2 = 0.60 for sheet thickness and r 2 = 0.53 for sheet load).

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“…While this might seem like quite a drastic step, conceptually it is really no different from using hiding/exposure functions to modify the grain fraction Shields parameter, as described in section 2.3. Also there is some experimental evidence that the velocity is indeed grainsize dependant, see Ahmed and Sato (2003), where coarse grains were found to move faster in a mixture than in isolation for the same flow conditions.…”

Section: Discussionmentioning

confidence: 97%

A Transport Model of Graded Sands in the Oscillatory Sheet-Flow Regime

Malarkey¹,

Davies²

2006

Coastal Dynamics 2005

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The 1DV two-layer model of oscillatory sheet flow of Malarkey et al. (2003) which was developed for a single grain size has been modified to include grain fractions. The model includes a suspension layer above a sheet-flow layer consisting of prescribed profiles of concentration and velocity. Since this model keeps track of the total sediment in the water column through the wave cycle it is ideally suited for representing graded sediments. The modified model has been compared with the graded sediment data of Hassan et al. (1999). The results show that the model can reproduce the statistical characteristics of the sediment in suspension and produces fractional transport rates that are consistent with the experiments. However, it also demonstrates that a sediment weighting function limited by the amount of sediment in suspension is not sufficient to give rise to the apparent effects of hiding and exposure seen in the data.

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A Sheetflow Transport Model for Asymmetric Oscillatory Flows Part II: Mixed Grain Size Sediments

Cited by 18 publications

References 7 publications

A semianalytical model for sheet flow layer thickness with application to the swash zone

A semianalytical model for sheet flow layer thickness with application to the swash zone

Comprehensive Field Study of Swash-Zone Processes. II: Sheet Flow Sediment Concentrations during Quasi-Steady Backwash

A Transport Model of Graded Sands in the Oscillatory Sheet-Flow Regime

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