Turbulence Structure of Hydraulic Jumps of Low Froude Numbers

Liu, Minnan; Rajaratnam, N.; Zhu, David Z.

doi:10.1061/(asce)0733-9429(2004)130:6(511)

Cited by 121 publications

(64 citation statements)

References 17 publications

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“…We found that the Reynolds shear stresses exhibit self similar ity, as reported from experiments in a similar flow by Liu et al [11]. The Reynolds stresses in our experiments have been calculated by subtracting the mean values of the horizontal and vertical velocity components to the instantaneous velocities and then calculating the ensemble average of the product of horizontal and vertical velocity fluctuations.…”

Section: Self Similaritysupporting

confidence: 84%

“…The resulting self similar shear stresses are well approximated by a gaussian distribution (solid line) as suggested by Townsend [29] for a free mixing layer. It is interesting to point out that the similarity variable employed here is not the one used by Liu et al [11]. The difference is that the origin of our variable is a fixed reference of the mixing layer (y = y 0.1 ) instead of the bottom of the channel, as Liu et al [11] pro pose.…”

Section: Self Similaritymentioning

confidence: 96%

“…It is interesting to point out that the similarity variable employed here is not the one used by Liu et al [11]. The difference is that the origin of our variable is a fixed reference of the mixing layer (y = y 0.1 ) instead of the bottom of the channel, as Liu et al [11] pro pose. This choice is not only preferable in order to apply our results to other steady breakers found in deep water flows, but also yields a better collapse in the dimensionless shear stress profiles, as can be seen comparing Fig.…”

Section: Self Similaritymentioning

confidence: 96%

“…They obtained mean velocity and shear stress profiles that clearly showed the existence of a shear layer. More recently Liu et al [11] used Doppler ultrasound velocimetry to characterize the turbulent stresses in low Froude number hydraulic jumps, where the void fraction is small enough for this technique to operate properly. These authors found the maximum Reynolds stress at the center line of the mixing layer, where the turbulent intensities were greater than 20%.…”

mentioning

confidence: 99%

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Dynamics of large turbulent structures in a steady breaker

Rodríguez-Rodríguez

Marugán-Cruz

Aliseda

et al. 2011

Experimental Thermal and Fluid Science

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a b s t r a c tThe flow near the leading edge of a steady breaker has been studied experimentally using Bubble Image Velocimetry (BIV) with the aim of characterizing the dynamics of the large eddies responsible for air entrainment. It is well reported in the literature, and confirmed by our measurements of the instanta neous velocity field, that this flow shares some important features with the turbulent shear layer formed between two parallel semi infinite streams with different velocities. Namely, the formation of a periodic array of coherent vortices, the constant convective velocity of those vortices, the linear relation between their size and their downstream position and the self similar structure of both mean velocity profiles and Reynolds shear stresses. Nonetheless, important differences exists between the dynamics of the large eddies in a steady breaker and those in a free shear layer. Particularly, the convective velocity of these large structures is slower in a steady breaker and, consistent with this, their growth rates are larger. A physical interpretation of these differences is provided together with a discussion of their implications. To support our measurements and conclusions, we present a careful analysis of the accuracy of the BIV technique in turbulent flows with large bubbles.

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Section: Self Similaritysupporting

confidence: 84%

Section: Self Similaritymentioning

confidence: 96%

Section: Self Similaritymentioning

confidence: 96%

mentioning

confidence: 99%

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Dynamics of large turbulent structures in a steady breaker

Rodríguez-Rodríguez

Marugán-Cruz

Aliseda

et al. 2011

Experimental Thermal and Fluid Science

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“…All of these points depend on the turbulence characteristics and transport of turbulent kinetic energy (TKE) by means of turbulent velocity fluctuations in the flow (Blanckaert and De Vriend 2005a, b;Lee et al 2012;Lien and D'Asaro 2006;Liu et al 2004;Shvidchenko and Pender 2001). In spite of this practical relevance, a lot of ground is to be covered on turbulence characteristics in open channel and near hydraulic structures.…”

Section: Introductionmentioning

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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Flow and turbulence structure in a hypertidal estuary with the world's biggest tidal bore

Fan

2017

JGR Oceans

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Turbulent and flow structure associated with breaking tidal bores are deliberately investigated on the basis of field measurements. High‐resolution velocity and hydrographic data are collected in the middle Qiantang Estuary by a vertical array of acoustic Doppler velocimeters and optical backscatter sensors, collaborated with a bottom‐mounted acoustic Doppler current profiler. Besides obvious variations in diurnal and spring‐neap tidal cycles, the estuarine dynamics is featured by extreme asymmetry in flood and ebb tides. The flood tide is abnormally accelerated to generate tidal bores at the first 10 min or more, with breaking or undular configurations at the front. The occurrence of peak flow velocity, turbulent kinetic energy (TKE), and TKE dissipation rate (ε) is definitely associated with breaking bores, with their values several times to 2 orders of magnitude larger than the corresponding secondary peak values during the maximum ebb flows. Flow and turbulence dynamics are significantly affected by the tidal‐bore Froude number. A sandwich ε structure is clear exhibited with the maximum value at the surface, secondary maximum near the bed, and the minimum at the intermediate. Dual TKE sources are indicated by an approximate local balance between shear production and dissipation near the bottom, and a top‐down TKE dissipation using the modified Froude scaling in the vertical water column. The highly elevated dissipation by breaking bores is comparable to that by intense breaking waves in the surf zone, and the former potentially penetrates the entire water column to produce extreme sediment‐resuspension events in combination with intense bottom shear stress.

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Turbulence Structure of Hydraulic Jumps of Low Froude Numbers

Cited by 121 publications

References 17 publications

Dynamics of large turbulent structures in a steady breaker

Dynamics of large turbulent structures in a steady breaker

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

Flow and turbulence structure in a hypertidal estuary with the world's biggest tidal bore

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