A two-phase numerical model for sediment transport prediction under oscillatory sheet flows

Li, Ming; Pan, Shunqi; O’Connor, Brian A.

doi:10.1016/j.coastaleng.2008.05.003

Cited by 45 publications

(53 citation statements)

References 14 publications

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“…It differs in that aspect from sheet flow models that use near-bed empirical parameterizations for the reference concentration (e.g., Amoudry et al, 2005;Ruessink et al, 2009;Hassan and Ribberink, 2010) and for the bed load transport rate (e.g., Hassan and Ribberink, 2010). We also believe that it offers more insight on the small-scale physics involved than models that employ an empirical formulation for the sediment phase stresses (e.g., Dong and Zhang, 2002;Li et al, 2008).…”

Section: Model Descriptionmentioning

confidence: 92%

“…But some advanced small-scale local models are now able to fully resolve near-bed sediment transport and could thus be used to gain insight on the parameterizations pertinent to larger scale models. For example, detailed process models are now able to represent very near bed sediment behaviour under the sheet flow regime using descriptions of two-phase sediment fluid interactions (e.g., Dong and Zhang, 2002;Li et al, 2008) and granular flow dynamics (e.g., Jenkins and Hanes, 1998;Drake and Calantoni, 2001). Similar two-phase models have been developed for multi-dimensional studies (e.g., Zhao and Fernando, 2007;Amoudry and Liu, 2009), but their applications remain limited to scour problems.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Model Descriptionmentioning

confidence: 92%

Section: Introductionmentioning

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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“…It is worthwhile to point out that the importance to consider the dependence of the turbulence intensity on the sediment concentration has already been realized in a number of previous studies. Li et al (2008) introduced a concentration-weighted formula for the turbulent viscosity in their one-equation (k-equation) model, which decreases with the increase of the sediment concentration; Sato (2005, 2006) adopted a varying function of the vertical coordinate as their expression of the eddy viscosity; Dong and Zhang (2002) considered the dependence of the vertical diffusion coefficient on the sediment concentration. Amoudry et al (2008) employed a similar relation as Eq.…”

Section: Turbulence Modelmentioning

confidence: 99%

“…Turbulence modeling of the sheet flows, which are characterized by their high sediment concentration, is thus an unsolved problem. In practice, Katori et al (1996) adopted the one-equation (k-equation) model with an empirical formula for the turbulence energy dissipation rate, while Li et al (2008) applied the same one-equation model but required the turbulent viscosity and the dissipation to take different values in low and high concentration regions. Two-equation turbulence models adopted by Elghobashi and Abou-Arab (1983) and Hsu et al (2003) did not consider the effects of the sediment concentration.…”

Section: Turbulence Modelmentioning

confidence: 99%

“…That the mixing-length coefficient involved in the model is complicatedly related to the features of the flow also restricts its applicability. To enhance the turbulence modeling, Hsu et al (2003) applied the standard κ-ε model, while Li et al (2008) employed a one-equation model for simplicity. Bakhtyar et al (2009a;2009b) further included the advection effects but unreasonably neglected the diffusion terms in the continuity equations.…”

Section: Introductionmentioning

confidence: 99%

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A two-phase approach to wave-induced sediment transport under sheet flow conditions

Chen

Niu

et al. 2011

Coastal Engineering

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A numerical model for the general description of the sediment transport under oscillatory sheet flow conditions is developed based on a two-fluid representation of the two-phase turbulent flows. The governing equations of the model are the Reynolds averaged continuity equations and equations of motion for both the fluid and the sediment phases. The two phases are coupled by the interphase forces including the resistance force, the inertia force, and the lift force. Turbulence closure of the fluid phase is based on a slightly modified k-ε model while an algebraic particle-turbulence model is applied to the sediment phase. The numerical method is based on the modified SIMPLE scheme and an improved time stepping technique. The model is validated by the published data for the symmetrical oscillatory sheet flows generated in an oscillatory flow tunnel at the University of Tokyo and for both the symmetrical and the asymmetrical oscillatory sheet flows generated in an oscillatory flow tunnel at University of Aberdeen. The numerical results on the temporal and spacial variation of the sediment concentration, the horizontal velocities of the two phases, the horizontal and vertical fluxes of the sediment phase, as well as the thickness of the sheet flow layer all show satisfactory agreement with the laboratory data. The model is also shown to predict the net sediment transport rate with a reasonably good accuracy.

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Bottom‐slope‐induced net sheet‐flow sediment transport rate under sinusoidal oscillatory flows

Yuan

Madsen

2017

JGR Oceans

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It is generally believed that the slope of beaches can lead to a net downslope (usually offshore) sediment transport rate under shoaling waves, but very few high‐quality measurements have been reported for a quantitative understanding of this phenomenon. In this study, full‐scale (1:1) experiments of bottom‐slope‐induced net sheet‐flow sediment transport rate under sinusoidal oscillatory flows are conducted using a tilting oscillatory water tunnel. The tests cover a variety of flow‐sediment conditions on bottom slopes up to 2.6°. A laser‐based bottom profiler system is developed for measuring net transport rate based on the principle of mass conservation. Experimental results suggest that for a given flow‐sediment condition the net transport rate is in the downslope direction and increases linearly with bottom slope. A conceptual model is presented based on the idea that gravity helps bottom shear stress drive bedload transport and consequently enhances (reduces) bedload transport and suspension when the flow is in the downslope (up‐slope) direction. The model predicts both the measured net sediment transport rates and the experimental linear relationship between net transport rates and bottom slope with an accuracy generally better than a factor of 2. Some measured net transport rates in this study are comparable to those due to flow skewness obtained in similar sheet‐flow studies, despite that our maximum slope could be milder than the actual bottom slope in surf zones, where sheet‐flow conditions usually occur. This shows that the slope effect may be as important as wave nonlinearity in producing net cross‐shore sheet‐flow sediment transport.

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A two-phase numerical model for sediment transport prediction under oscillatory sheet flows

Cited by 45 publications

References 14 publications

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

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

A two-phase approach to wave-induced sediment transport under sheet flow conditions

Bottom‐slope‐induced net sheet‐flow sediment transport rate under sinusoidal oscillatory flows

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