Steady streaming and sediment transport at the bottom of sea waves

Blondeaux, Paolo; Vittori, Giovanna; Bruschi, Antonello; Lalli, F.; Pesarino, Valeria

doi:10.1017/jfm.2012.50

Cited by 34 publications

(43 citation statements)

References 49 publications

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“…The numerical procedure has been validated by comparing the obtained results with experimental data obtained for a flat bed, both in wave channels and in U-tubes. More details on the formulation of the problem and the numerical approach can be found in Blondeaux et al (2012). and in the middle between the crests of two roughness elements.…”

Section: The Numerical Solutionmentioning

confidence: 99%

“…Even though the theoretical analysis seems to underestimate the steady velocity component for large values of A u , the agreement between the theoretical results and the experimental measurements is fair, also taking into account the scatter of the laboratory data. More validation tests can be found in Blondeaux et al (2012).…”

Section: The Numerical Solutionmentioning

confidence: 99%

“…Recently, Blondeaux et al (2012) have focussed their attention in the bottom boundary layer under a propagating sea wave and have determined the flow and the sediment transport by assuming that the sea bottom is flat. Their results show that the steady velocity component and the net (wave averaged) sediment transport are different from those generated by asymmetrical fluid oscillations in an oscillating water tunnel (U-tube) even if the values of the significant parameters (amplitude and period of the fluid oscillations, asymmetry index) are the same.…”

mentioning

confidence: 99%

“…Their results show that the steady velocity component and the net (wave averaged) sediment transport are different from those generated by asymmetrical fluid oscillations in an oscillating water tunnel (U-tube) even if the values of the significant parameters (amplitude and period of the fluid oscillations, asymmetry index) are the same. The analysis of Blondeaux et al (2012) considers large values of the Shields parameter such that the small scale bedforms (ripples), which are usually generated by the interaction of sea waves with a cohesionless sandy bottom, are washed out and the bottom can be assumed to be flat. Even though large values of the Shields parameter are usually found in the nearshore region during storms, for mild weather conditions the shoaling region is characterized by moderate or relatively small values of the Shields parameter such that the sea bottom is rippled (Sleath, 1984).…”

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confidence: 99%

“…Even though large values of the Shields parameter are usually found in the nearshore region during storms, for mild weather conditions the shoaling region is characterized by moderate or relatively small values of the Shields parameter such that the sea bottom is rippled (Sleath, 1984). Motivated by the finding of Chowdhury et al (1997) on the relevant effect of bottom roughness on the bottom boundary layer, presently, the analysis of Blondeaux et al (2012) is extended to take into account the effect of the presence of ripples on the steady streaming.…”

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Sediment Transport at the Bottom of Sea Waves

Vittori

Blondeaux

2012

Int. Conf. Coastal. Eng.

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The flow in the wall boundary layer generated close to the sea bottom by the propagation of a monochromatic surface wave is determined by considering small values of both the wave steepness and the ratio between the thickness of the boundary layer and the local water depth. Depending on the hydrodynamic conditions, the sea bottom can be plane or rippled. The geometrical characteristics of the bottom forms are predicted using empirical formulae and, then, the bedforms are assumed to behave as a bottom roughness, the size of which is related to the size of the ripples. The bottom boundary layer is assumed to be turbulent and the flow field is computed by means of a two-equation turbulence model. Then the sediment transport is evaluated. The bed load is obtained using an empirical relationship. The suspended load is determined by computing the sediment flux, once the spatial and temporal distribution of sediment concentration is determined. A comparison of the model findings with the experimental results supports the approach.

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Section: The Numerical Solutionmentioning

confidence: 99%

Section: The Numerical Solutionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Sediment Transport at the Bottom of Sea Waves

Vittori

Blondeaux

2012

Int. Conf. Coastal. Eng.

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Stochastic interpretation of the advection-diffusion equation and its relevance to bed load transport

Ancey

Bohorquez

Heyman

2015

J. Geophys. Res. Earth Surf.

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The advection-diffusion equation is one of the most widespread equations in physics. It arises quite often in the context of sediment transport, e.g., for describing time and space variations in the particle activity (the solid volume of particles in motion per unit streambed area). Phenomenological laws are usually sufficient to derive this equation and interpret its terms. Stochastic models can also be used to derive it, with the significant advantage that they provide information on the statistical properties of particle activity. These models are quite useful when sediment transport exhibits large fluctuations (typically at low transport rates), making the measurement of mean values difficult. Among these stochastic models, the most common approach consists of random walk models. For instance, they have been used to model the random displacement of tracers in rivers. Here we explore an alternative approach, which involves monitoring the evolution of the number of particles moving within an array of cells of finite length. Birth-death Markov processes are well suited to this objective. While the topic has been explored in detail for diffusion-reaction systems, the treatment of advection has received no attention. We therefore look into the possibility of deriving the advection-diffusion equation (with a source term) within the framework of birth-death Markov processes. We show that in the continuum limit (when the cell size becomes vanishingly small), we can derive an advection-diffusion equation for particle activity. Yet while this derivation is formally valid in the continuum limit, it runs into difficulty in practical applications involving cells or meshes of finite length. Indeed, within our stochastic framework, particle advection produces nonlocal effects, which are more or less significant depending on the cell size and particle velocity. Albeit nonlocal, these effects look like (local) diffusion and add to the intrinsic particle diffusion (dispersal due to velocity fluctuations), with the important consequence that local measurements depend on both the intrinsic properties of particle displacement and the dimensions of the measurement system. Citation:Ancey, C., P. Bohorquez, and J. Heyman (2015), Stochastic interpretation of the advection-diffusion equation and its relevance to bed load transport, p particle volume (m 3 ).Gaussian noise increment (s −1∕2 ). b space and time Gaussian noise increment (m −1∕2 s −1∕2 ) .

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Three‐dimensional streaming in the seabed boundary layer beneath propagating waves with an angle of attack on the current

2015

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The effect of three‐dimensional wave‐induced streaming on the seabed boundary layer is investigated for following and opposing waves and current where the wave propagation forms a nonzero angle with the current. It is shown that the seabed boundary layer flow results from an interaction between the classical wave‐current interaction (reducing the mean velocity relative to current alone), Longuet‐Higgins streaming (forcing the flow in the wave propagation direction), and streaming caused by turbulence asymmetry in successive wave half‐cycles (forcing the flow against the wave propagation direction). For waves and current which are not colinear, the mean velocity profile exhibits a veering behavior which is strongly affected by streaming, particularly for the most wave‐dominated situations. The effect of streaming on the boundary layer flow has been investigated for different wave‐current conditions and bottom roughnesses. Visualizations are given by mean Eulerian and Lagrangian velocity profiles, as well as three‐dimensional seabed boundary layer particle trajectories. The effect of streaming decreases as the flow becomes more current dominated. The mean velocity in the current direction decreases as the roughness increases. However, the mean velocity orthogonal to the current direction increases as the roughness increases due to the lack of wave‐current interaction in this direction. An excellent agreement between the predicted and recently measured velocity profiles beneath horizontally uniform asymmetric forcing is obtained.

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Steady streaming and sediment transport at the bottom of sea waves

Cited by 34 publications

References 49 publications

Sediment Transport at the Bottom of Sea Waves

Sediment Transport at the Bottom of Sea Waves

Stochastic interpretation of the advection-diffusion equation and its relevance to bed load transport

Three‐dimensional streaming in the seabed boundary layer beneath propagating waves with an angle of attack on the current

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