Experimental and theoretical study of wave–current turbulent boundary layers

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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“…These results are in agreement with those of Holmedal et al . [, Figures and ] and Yuan and Madsen []. Similarly, the mean velocity component

\bar{u} (z)

for ( θ =

45 °

) and ( θ =

135 °

) are smaller and larger, respectively, than the corresponding velocity profiles

\bar{u} (z)

for symmetric horizontally uniform forcing (Figure a).…”

Section: Resultsmentioning

confidence: 67%

“…The velocity measurements by Yuan and Madsen [, Figure ] show that the asymmetric streaming velocity opposes the wave direction, leading to a larger magnitude of the mean velocity for opposing waves and current than for following waves and current. This behavior was earlier predicted qualitatively by Holmedal et al .…”

Section: Resultsmentioning

confidence: 99%

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

2015

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“…They determined a velocity increase in the case of waves propagating with the current and a decrease in the case of opposing flows. Recently, Yuan and Madsen (2015) measured the horizontally uniform turbulent wave-current bottom boundary layer flow subject to asymmetric forcing. They found that within the seabed boundary layer flow the magnitude of the mean velocity is larger for opposing than for following waves and current.…”

Section: Introductionmentioning

confidence: 99%

Waves plus currents crossing at a right angle: near-bed velocity statistics

Faraci

Scandura

Musumeci

et al. 2018

Journal of Hydraulic Research

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Wave-current flow over a bottom covered with different roughness elements was analysed to provide new insights into the statistical properties of the near-bed velocity. Experimental data were used from three different experimental campaigns, with orthogonal waves and currents over a sandy bed, a gravel bed and a rippled bed. Velocity profiles were acquired by means of a micro-ADV. The paper focuses on the effects that the waves have on the velocity statistics of the steady current. In particular, the near-bed velocities in the current direction closely follow a Gaussian distribution. When waves are added, the distribution becomes double-peaked. In order to get single-peaked velocity distributions the total velocity events in the current direction were decoupled by taking into account the sign of the wave directed velocities. The nature of the distribution functions is influenced by the mass conservation principle and, in the rippled bed case by the vorticity dynamics.

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“…They determined a velocity increase in the case of waves propagating with the current and a decrease in the case of opposing flows. Yuan and Madsen (2015) found that in the seabed boundary layer flow, the magnitude of the mean velocity is larger for opposing than for following waves and current.…”

Section: Introductionmentioning

confidence: 96%

Wave-Current Interaction Over Seabeds With Different Roughness: A Statistical Analysis

Faraci

Scandura

Foti

2017

Int. Conf. Coastal. Eng.

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Wave-current flow over seabeds covered with different roughness has been studied in order to deepen the knowledge on the statistical properties of the near-bed velocity. The results of three different experimental campaigns performed in the presence of a sandy bed, a gravel bed and a rippled bed, carried out superimposing a steady current onto an orthogonal wave, have been analysed. The statistics of the current velocity, including the wave effects on the steady current have been investigated. It has been observed that in the absence of waves, the fluctuations of the near-bed velocities closely follow a Gaussian distribution. When waves are also present, in order to obtain consistent near-bed velocity statistics, it is necessary to decouple the velocity events in the current direction by taking into account the sign of the wave velocities. In the latter case, the nature of the distribution functions is influenced by the mass conservation principle. A Gaussian distribution well describes the turbulent fluctuations obtained by removing the phase averaged velocity from the current velocity.

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Experimental and theoretical study of wave–current turbulent boundary layers

Cited by 48 publications

References 44 publications

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

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

Waves plus currents crossing at a right angle: near-bed velocity statistics

Wave-Current Interaction Over Seabeds With Different Roughness: A Statistical Analysis

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