Numerical simulation of two-phase flow for sediment transport in the inner-surf and swash zones

Bakhtyar, Roham; Barry, David Andrew; Yeganeh‐Bakhtiary, Abbas; Li, Ling; Parlange, J.‐Y.; Sander, G. C.

doi:10.1016/j.advwatres.2009.12.004

Cited by 38 publications

(31 citation statements)

References 45 publications

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“…This is consistent with the reduced magnitude, relative to an intermediate beach, of turbulence, flow velocity, momentum and wave energy after breaking that occurs on dissipative beaches during both the uprush and backwash (Miles et al, 2006). These results are also consistent with the field results of Miles et al (2006) and the numerical results of Bakhtyar et al (2010a). They indicated that the sediment transport and concentrations are greater on intermediate beaches than on dissipative beaches.…”

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confidence: 81%

Numerical experiments on interactions between wave motion and variable-density coastal aquifers

Bakhtyar

Barry

Brovelli

2012

Coastal Engineering

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A comprehensive two-dimensional (cross-shore) process-based numerical model of nearshore hydrodynamics (based on the Navier-Stokes equations, k-ε turbulence closure and the Volume-Of-Fluid method), beach morphology, and variable-density groundwater flow (SEAWAT-2000) was developed. This model, which was applied at the field scale, relaxes simplifications in existing models that do not include such detailed mechanistic descriptions. Numerical experiments were conducted to investigate the effects of varying aquifer, beach and wave characteristics (e.g., inland groundwater head, sand grain size, different wave heights and periods) on the coupled system. Spilling and plunging breakers on dissipative and intermediate beaches were simulated. For a given set of boundary conditions, the model was run for 1 y without the hydrodynamic sub-model to achieve a realistic salt-/freshwater interface. Then, the hydrodynamic component was run for 15 min and the model results analyzed. The main features considered were groundwater circulation, saltwater wedge position, in/exfiltration across the beach face, and beach morphology. The predictions of the numerical model agree well with existing understanding and experimental measurements. For an inland watertable that is lower than the still water level (SWL), such that the groundwater flow is mainly landward, on both coarse and fine sand beaches the addition of wave motion moves the saltwater wedge further landward. For an inland watertable that is higher than the SWL, the opposite behavior occurred. The numerical experiments showed that more sediment transport takes place on intermediate beaches than on dissipative beaches. In addition, beach profile variations are greater under plunging breakers, while coarse sand beaches are steeper than fine sand beaches for the same wave conditions. There is a strong correlation between in/exfiltration and beach face deposition/erosion for the coarse beaches, while in/exfiltration has a slight effect on sediment transport for fine beaches. The model is capable of simulating the short-term evolution of foreshore profile changes, and beach 3 watertable and saltwater wedge movement due to interactions between wave motion and coastal groundwater. IntroductionMost previous investigations concerned with modeling of interactions between ocean water and coastal groundwater focused on tide-induced watertable fluctuations, neglecting high-frequency wave-induced oscillations and variable-density groundwater flow (e.g., Teo et al., 2003;Brovelli et al., 2007;Robinson et al., 2007bRobinson et al., , 2009Slooten et al., 2010;Li et al., , 2007Xin et al., 2010). However, given the interplay of mechanisms inherent in coastal processes -mixing of fresh-and seawater driven by waves, sediment transport and beach profile changes -it is not possible to extrapolate readily existing results to realistic coastal zone behavior.Waves in the nearshore zone are an important forcing on sediments and groundwater behavior. While waves induce instantaneous pore wat...

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confidence: 81%

Numerical experiments on interactions between wave motion and variable-density coastal aquifers

Bakhtyar

Barry

Brovelli

2012

Coastal Engineering

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“…This is mainly due to the creeping motion of the breaking wave, momentum exchange, collision of the breaking wave front onto the flow below, shear flow underneath the free surface and vortices near the wave crest. Therefore, numerical models based on the hydrostatic pressure distribution (e.g., depth-averaged models like the non- 23 linear shallow water equation) are not precise. However, RANS models are able to simulate reasonably details of the flow and turbulence fields.…”

Section: Pressure Distributionmentioning

confidence: 99%

Air–water two-phase flow modeling of turbulent surf and swash zone wave motions

Bakhtyar

Razmi

Barry

et al. 2010

Advances in Water Resources

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Wave breaking and wave runup/rundown have a major influence on nearshore hydrodynamics, morphodynamics and beach evolution. In the case of wave breaking, there is significant mixing of air and water at the wave crest, along with relatively high kinetic energy, so prediction of the free surface is complicated. Most hydrodynamic studies of surf and swash zone are derived from single-phase flow, in which the role of air is ignored. Two-phase flow modeling, consisting of both phases of water and air, may be a good alternative numerical modeling approach for simulating nearshore hydrodynamics and, consequently, sediment transport. A two-phase flow tool can compute more realistically the shape of the free surface, while the effects of air are accounted for. This paper used models based on two-dimensional, two-phase Reynolds-Averaged NavierStokes equations, the Volume-Of-Fluid surface capturing technique and different turbulence closure models, i.e., k-ε, k-ω and Re-Normalized Group (RNG). Our numerical results were compared with the available experimental data. Comparison of the employed method with a model not utilizing a two-phase flow modeling demonstrates that including the air phase leads to improvement in simulation of wave characteristics, especially in the vicinity of the breaking point.The numerical results revealed that the RNG turbulence model yielded better predictions of nearshore zone hydrodynamics, although the k-ε model also gave satisfactory predictions. The model provides new insights for the wave, turbulence and means flow structure in the surf and swash zones.

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“…In contrast, the near-bed layer in the inner surf and swash zones is directly affected by bore-generated turbulence [Puleo et al, 2000;Butt et al, 2004;Jackson et al, 2004;Aagaard and Hughes, 2006;. The impact of breaking wave-generated turbulence on the sheet flow layer has only recently been investigated Two-phase numerical models that resolve the granular dynamics and sediment-fluid interactions have led to an improved understanding of sheet flow [Hsu et al, 2004;Calantoni and Puleo, 2006;Amoudry et al, 2008;Bakhtyar et al, 2009Bakhtyar et al, , 2010Chen et al, 2011]. However, the mechanics of sheet flow are not yet fully understood, especially in complex natural environments such as the swash zone.…”

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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Numerical simulation of two-phase flow for sediment transport in the inner-surf and swash zones

Cited by 38 publications

References 45 publications

Numerical experiments on interactions between wave motion and variable-density coastal aquifers

Numerical experiments on interactions between wave motion and variable-density coastal aquifers

Air–water two-phase flow modeling of turbulent surf and swash zone wave motions

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

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