Experiments on the turbulence statistics and the structure of a reciprocating oscillatory flow

Hino, Masahiro; Kashiwayanagi, Masayuki; Nakayama, Akihiko; Hara, Tatsuhiko

doi:10.1017/s0022112083001378

Cited by 240 publications

(215 citation statements)

References 17 publications

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“…Here, explosive turbulent near-wall bursts appear during the deceleration phase, while the flow relaminarizes during acceleration. 6 For higher Re S , the flow becomes turbulent in earlier phases and remains turbulent for longer periods. A study by Jensen et al 2 showed that fully developed turbu-lence is already present during most of the oscillation cycle at Re S ϳ 1800, while the flow remains turbulent during the complete cycle for Re S Ͼ 3500.…”

Section: Introductionmentioning

confidence: 97%

Turbulent oscillating channel flow subjected to a free-surface stress

2010

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The channel flow subjected to a wind stress at the free surface and an oscillating pressure gradient is investigated using large-eddy simulations. The orientation of the surface stress is parallel with the oscillating pressure gradient and a purely pulsating mean flow develops. The Reynolds number is typically Reω=106 and the Keulegan–Carpenter number—the ratio between the oscillation period and advection time scale—is KC=80. Results compare favorably to the data from direct numerical simulations obtained over a single period. A slowly pulsating mean flow occurs with the turbulent flow essentially being statistically steady. Logarithmic boundary layers are present at both the bottom wall and the free surface. Turbulent streaks are observed in the bottom and free-surface layer. The viscous sublayer below the free surface is, however, much thinner. This observation is verified by simulations we performed for a purely wind-driven channel flow. For the oscillating flow, additional low-speed splats (localized regions of upwelling) occur at the free surface when the mean velocity and stress are in the same direction.

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Section: Introductionmentioning

confidence: 97%

Turbulent oscillating channel flow subjected to a free-surface stress

2010

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“…The turbulence near a hydraulic structure has been the subject of theoretical and experimental research for the past few decades due to sediment transport (Hino et al 1983;Nagata et al 2005;Raupach et al 1991;Raupach and Thom 1981;Speziale 1990). Sediment transport is highly intermittent and it was hypothesized that this was due to an intermittence of the turbulent intensities caused by coherent structures of the turbulent flow field (Grass 1971;Raupach et al 1996;Rhoads and Massey 2012).…”

Section: Parameters and Methodsmentioning

confidence: 99%

Turbulence study in the vicinity of piano key weir: relevance, instrumentation, parameters and methods

Tiwari

Sharma

2015

Appl Water Sci

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This research paper focuses on the need of turbulence, instruments reliable to capture turbulence, different turbulence parameters and some advance methodology which can decompose various turbulence structures at different levels near hydraulic structures. Small-scale turbulence research has valid prospects in open channel flow. The relevance of the study is amplified as we introduce any hydraulic structure in the channel which disturbs the natural flow and creates discontinuity. To recover this discontinuity, the piano key weir (PKW) might be used with sloped keys. Constraints of empirical results in the vicinity of PKW necessitate extensive laboratory experiments with fair and reliable instrumentation techniques. Acoustic Doppler velocimeter was established to be best suited within range of some limitations using principal component analysis. Wavelet analysis is proposed to decompose the underlying turbulence structure in a better way.

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“…(7) (8) (degree) (9) Hereafter, the values of a, as function of a from three approximation of phase difference are plotted in Fig. 8.…”

Section: Experimental Methodsmentioning

confidence: 99%

New Method for Calculating Bottom Shear Stress under Skew Waves

Suntoyo

Tanaka

Yamaji

2004

Journal of applied mechanics

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The bottom shear stress under skew waves can be used in a sediment transport modeling under rapid acceleration occurring in the surf zone. The bottom shear stress in a rough turbulent bottom boundary layer under sawtooth waves has been examined through two methods by Suntoyo and Tanaka°. One is to fit logarithmic velocity profile to the measured velocity in an oscillating wind tunnel, another is a calculation method incorporating acceleration effect. However, an investigation of a more reliable calculation method to estimate the time-variation of bottom shear stress has not been fully dealt with.In the present study, the bottom shear stress of experimental result will be examined with a new calculation method of bottom shear stress based on incorporating velocity and acceleration terms all at once. A new coefficient is proposed to express a wave skewness effect on bottom shear stress under skew waves.

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Experiments on the turbulence statistics and the structure of a reciprocating oscillatory flow

Cited by 240 publications

References 17 publications

Turbulent oscillating channel flow subjected to a free-surface stress

Turbulent oscillating channel flow subjected to a free-surface stress

Turbulence study in the vicinity of piano key weir: relevance, instrumentation, parameters and methods

New Method for Calculating Bottom Shear Stress under Skew Waves

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