A Dynamical and Visual Study on the Oscillatory Turbulent Boundary Layer

Hayashi, Taizo; Ohashi, Masakazu

doi:10.1007/978-3-642-95410-8_3

Cited by 14 publications

(17 citation statements)

References 6 publications

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“…Horizontal and vertical advection, production, and dissipation are the dominant terms in the near-bed TKE balance A two-dimensional (horizontal 1 vertical) clockwise circulation advects wave breaking TKE through the near-bed layer Flow nonuniformity and the presence of energetic anisotropic wave breaking turbulence enhances near-bed turbulence production Much of our knowledge of WBL turbulence dynamics originates from flow visualizations (Carstensen et al, 2010(Carstensen et al, , 2012Hayashi & Ohashi, 1982;Sarpkaya, 1993) and turbulent velocity measurements (Akhavan et al, 1991;Hino et al, 1983;Jensen et al, 1989;Sleath, 1987;van der A et al, 2011;Yuan & Dash, 2017) in oscillatory flow tunnel studies. Turbulence measurements in the WBL under nonbreaking surface waves are limited, but have been conducted at full scale (Conley & Inman, 1992;Foster et al, 2006) and small-scale (Henriquez et al, 2014;Kemp & Simons, 1982, 1983, generally showing behavior that is similar to tunnel observations.…”

Section: Key Pointsmentioning

confidence: 99%

“…In wave-generated bed boundary layers at full scale, turbulence is unsteady and builds up and decays during each half-cycle. Turbulence is initially generated at the bed during the accelerating flow phase in the form of longitudinal low-speed streaks, which then break up into smaller-scale vortices that merge and produce a burst of turbulence during the decelerating stage of the half-cycle (Carstensen et al, 2010;Costamagna et al, 2003;Hayashi & Ohashi, 1982;Scandura et al, 2016;Vittori & Verzicco, 1998). Consequently, turbulent intensities and Reynolds stress at the bed increase during flow acceleration and reach a maximum during the decelerating phase (e.g., Jensen et al, 1989).…”

Section: Key Pointsmentioning

confidence: 99%

“…Consequently, turbulent intensities and Reynolds stress at the bed increase during flow acceleration and reach a maximum during the decelerating phase (e.g., Jensen et al, 1989). As turbulence diffuses upward, turbulent intensities and Reynolds stresses show a progressive time lag with elevation, relative to their phase behavior at the bed (e.g., Hayashi & Ohashi, 1982;Hino et al, 1983;Jensen et al, 1989;van der A et al, 2011). The precise spatial and temporal turbulent behavior of oscillatory flows depends on Reynolds number and bed roughness (e.g., Jensen et al, 1989).…”

Section: Key Pointsmentioning

confidence: 99%

“…Much of our knowledge of WBL turbulence dynamics originates from flow visualizations (Carstensen et al, ; Hayashi & Ohashi, ; Sarpkaya, ) and turbulent velocity measurements (Akhavan et al, ; Hino et al, ; Jensen et al, ; Sleath, ; van der A et al, ; Yuan & Dash, ) in oscillatory flow tunnel studies. Turbulence measurements in the WBL under nonbreaking surface waves are limited, but have been conducted at full scale (Conley & Inman, ; Foster et al, ) and small‐scale (Henriquez et al, ; Kemp & Simons, ), generally showing behavior that is similar to tunnel observations.…”

Section: Introductionmentioning

confidence: 99%

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Near‐Bed Turbulent Kinetic Energy Budget Under a Large‐Scale Plunging Breaking Wave Over a Fixed Bar

Zanden

Caceres

et al. 2018

JGR Oceans

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Hydrodynamics under regular plunging breaking waves over a fixed breaker bar were studied in a large‐scale wave flume. A previous paper reported on the outer flow hydrodynamics; the present paper focuses on the turbulence dynamics near the bed (up to 0.10 m from the bed). Velocities were measured with high spatial and temporal resolution using a two component laser Doppler anemometer. The results show that even at close distance from the bed (1 mm), the turbulent kinetic energy (TKE) increases by a factor five between the shoaling, and breaking regions because of invasion of wave breaking turbulence. The sign and phase behavior of the time‐dependent Reynolds shear stresses at elevations up to approximately 0.02 m from the bed (roughly twice the elevation of the boundary layer overshoot) are mainly controlled by local bed‐shear‐generated turbulence, but at higher elevations Reynolds stresses are controlled by wave breaking turbulence. The measurements are subsequently analyzed to investigate the TKE budget at wave‐averaged and intrawave time scales. Horizontal and vertical turbulence advection, production, and dissipation are the major terms. A two‐dimensional wave‐averaged circulation drives advection of wave breaking turbulence through the near‐bed layer, resulting in a net downward influx in the bar trough region, followed by seaward advection along the bar's shoreward slope, and an upward outflux above the bar crest. The strongly nonuniform flow across the bar combined with the presence of anisotropic turbulence enhances turbulent production rates near the bed.

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Section: Key Pointsmentioning

confidence: 99%

Section: Key Pointsmentioning

confidence: 99%

Section: Key Pointsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Near‐Bed Turbulent Kinetic Energy Budget Under a Large‐Scale Plunging Breaking Wave Over a Fixed Bar

Zanden

Caceres

et al. 2018

JGR Oceans

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“…Other authors, Sawamoto et al [26], Obasaju et al [20] and Jensen [13], used seeding particles to visualize the flow and to propose a classification of the different regimes. Hayashi et al [9], Medeiros at al. [17,18] realized a velocity field mapping around a cylinder with a Laser Doppler Velocimeter.…”

Section: Introductionmentioning

confidence: 99%

Flow visualisation around a horizontal cylinder near a plane wall and subject to waves

Mouazé¹,

Bélorgey²

2003

Applied Ocean Research

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This study is motivated by the description and the understanding of the vortices formation and development near a cylinder subject to waves and under the influence of the bed. The results presents a classification of flow types for different gap-to-diameter ratio and for two cylinder diameters (D1 = 10 cm and D2 = 4 cm, 0.8m long) according to a systematic wave conditions range. The flow visualisations reveal different mechanisms of separation, development and growth of vortices depending on the Keulegan Carpenter number (0.5 < KC < 26) and the influence of the bed proximity. A flow asymmetry was observed between the crest and the trough of the wave and a stronger vortex activity downstream the cylinder especially for the highest gap-diameter ratios. Furthermore the vortices are rotating preferentially in the same sense than the orbital motion. The flow tends to become more similar to a planar oscillating flow when the cylinder is closer to the bed. The emergence of instabilities in the wake of the cylinder for the highest wave amplitude leads us to measure the velocities in the cylinder axis in order to quantify three-dimensional effects.

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The flow over bedload sheets and sorted bedforms

Blondeaux

Vittori

2014

Continental Shelf Research

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A Dynamical and Visual Study on the Oscillatory Turbulent Boundary Layer

Cited by 14 publications

References 6 publications

Near‐Bed Turbulent Kinetic Energy Budget Under a Large‐Scale Plunging Breaking Wave Over a Fixed Bar

Near‐Bed Turbulent Kinetic Energy Budget Under a Large‐Scale Plunging Breaking Wave Over a Fixed Bar

Flow visualisation around a horizontal cylinder near a plane wall and subject to waves

The flow over bedload sheets and sorted bedforms

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