Modeling the turbulent boundary layer at the bottom of sea wave

Blondeaux, Paolo; Vittori, Giovanna; Porcile, Gaetano

doi:10.1016/j.coastaleng.2018.08.012

Cited by 13 publications

(9 citation statements)

References 25 publications

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“…Turbulence appears during the decelerating phases, but the flow recovers a laminar-like behaviour during the accelerating phases (intermittently turbulent regime). As discussed in Blondeaux et al (2018), it can be easily verified that the intermittently turbulent regime is present in a significant part of the coastal region which shifts towards the shore during mild wave conditions while it shifts towards the offshore region during storms.…”

Section: Introductionmentioning

confidence: 87%

Interface-resolved direct numerical simulations of sediment transport in a turbulent oscillatory boundary layer

et al. 2020

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The flow within an oscillatory boundary layer, which approximates the flow generated by propagating sea waves of small amplitude close to the bottom, is simulated numerically by integrating Navier-Stokes and continuity equations. The bottom is made up of spherical particles, free to move, which mimic sediment grains. The approach allows to fully-resolve the flow around the particles and to evaluate the forces and torques that the fluid exerts on their surface. Then, the dynamics of sediments is explicitly computed by means of Newton-Euler equations. For the smallest value of the flow Reynolds number presently simulated, the flow regime turns out to fall in the intermittently turbulent regime such that turbulence appears when the free stream velocity is close to its largest values but the flow recovers a laminar like behaviour during the remaining phases of the cycle. For the largest value of the Reynolds number turbulence is significant almost during the whole flow cycle. The evaluation of the sediment transport rate allows to estimate the reliability of the empirical predictors commonly used to estimate the amount of sediments transported by the sea waves. For large values of the Shields parameter, the sediment flow rate during the accelerating phases does not differ from that observed during the decelerating phases. However, for relatively small values of the Shields parameter, the amount of moving particles depends not only on the bottom shear stress but also on flow acceleration. Moreover, the numerical results provide information on the role that turbulent eddies have on sediment dynamics. *

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Section: Introductionmentioning

confidence: 87%

Interface-resolved direct numerical simulations of sediment transport in a turbulent oscillatory boundary layer

et al. 2020

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“…At the wall, both the velocity and the turbulent kinetic energy are forced to vanish. The boundary condition at the wall for the pseudo-vorticity, which appears in the turbulence model, is forced following Blondeaux et al (2018).…”

Section: The Problem and The Numerical Modelmentioning

confidence: 99%

RANSE Modeling of the Oscillatory Flow Over Two‐Dimensional Rigid Ripples

Sishah

Vittori

2022

JGR Oceans

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In the nearshore region, the hydrodynamics and the sediment transport are highly affected by the interaction of the waves with the sea bottom. Often the sea bed is covered with small-scale undulations, called ripples .In the coastal region, the ripples generated by surface waves are characterized by wavelengths of the order of tens of centimeters and heights of the order of centimeters. Moreover, ripples can be either two-dimensional (long-crested ripples) or three-dimensional.Ripples are relevant from a practical point of view because they influence both the surface wave and the sediment transport. Indeed, ripples dissipate wave energy because of the vortices which are generated each half oscillation cycle at the ripple crest. Such vortices influence also the near-bottom sediment transport, because they are particularly effective in picking up the sediment from the bottom and they influence the spatial and temporal evolution of sediment concentration close to the sea bed.At the early stages of their development, two-dimensional ripples have a small height. These bottom features are called rolling-grain ripples (Sleath, 1984). The mechanism of formation of rolling-grain ripples from a plane bed subject to an oscillatory flow is associated to the formation of steady recirculating cells which form because of the interaction of the bottom profile, which is characterized by a waviness of small amplitude, with the oscillatory flow (Sleath, 1984). The steady velocity components close to the bottom profile are directed from the troughs toward the crests of the waviness, thus dragging the sediment and causing the growth of the ripples. Vittori (1989) showed that the number of steady recirculating cells per ripple wavelength can be two or four, depending on the values of the controlling parameters.Typically rolling-grain ripples evolve into vortex ripples. Stable rolling grain ripples are observed mainly in laboratory experiments.

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“…This review paper does not focus on the different turbulence models and Blondeaux et al [55] provides a detailed description of the flow-structure by comparing various turbulence models. However, it should be noted that, in the study of wave-structureseabed interactions, the most appropriate turbulence model should provide an accurate description of (i) the flow close to the bottom (seabed surface) to obtain a reliable evaluation of the sediments transported by the flow [56] and (ii) the turbulent flow generated by the interactions with the structure.…”

Section: Turbulence Modelmentioning

confidence: 99%

Advances in Numerical Reynolds-Averaged Navier–Stokes Modelling of Wave-Structure-Seabed Interactions and Scour

Díaz-Carrasco

Croquer

Tamimi

et al. 2021

JMSE

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This review paper presents the recent advances in the numerical modelling of wave–structure–seabed interactions. The processes that are involved in wave–structure interactions, which leads to sediment transport and scour effects, are summarized. Subsequently, the three most common approaches for modelling sediment transport that is induced by wave–structure interactions are described. The applicability of each numerical approach is also included with a summary of the most recent studies. These approaches are based on the Reynolds-Averaged Navier–Stokes (RANS) equations for the fluid phase, and mostly differ in how they tackle the seabed response. Finally, future prospects of research are discussed.

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Modeling the turbulent boundary layer at the bottom of sea wave

Cited by 13 publications

References 25 publications

Interface-resolved direct numerical simulations of sediment transport in a turbulent oscillatory boundary layer

Interface-resolved direct numerical simulations of sediment transport in a turbulent oscillatory boundary layer

RANSE Modeling of the Oscillatory Flow Over Two‐Dimensional Rigid Ripples

Advances in Numerical Reynolds-Averaged Navier–Stokes Modelling of Wave-Structure-Seabed Interactions and Scour

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