Evaluation of ADV Measurements in Bubbly Two-Phase Flows

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

doi:10.1061/40655(2002)57

Cited by 30 publications

(10 citation statements)

References 14 publications

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“…The results established a cut-off frequency (-3dB) of 12Hz which is quite reasonable considering previous studies. Liu et al [6] found a cut-off frequency of 7Hz. During the hydraulic jump measurements 640 samples were collected at a rate of 128Hz.for each position,…”

Section: Free Surface Measurementsmentioning

confidence: 98%

Turbulence at Free Surface in Hydraulic Jumps

2004

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In the context of recent work by Brocchini & Peregrine [1,2], this paper aims to document free surface profiles, and turbulence length scales in hydraulic jumps with Froude numbers between 1.98 and 4.82. Although information on bubble size, frequency and velocities in hydraulic jumps is available in the literature, there is not much data on the features of the free surface, or on mixing layer thickness. In the present case, measurements at the free surface have been realized with two miniature resistive wire gauges each comprising two parallel 50 micron diameter wires with a separation of 1mm. These instruments were calibrated dynamically over a range of frequencies up to 20 Hz. Furthermore optical probes were used to measure properties of the air phase within the jump, including void fractions (up to 98%). The present results extend the range of Froude numbers for which two-phase measurements in hydraulic jumps are available, and, in most respects, confirm earlier results obtained with different experimental techniques. Length scales at the free surface are deduced from cross-correlation analysis of wire gauge measurements, and are compared with similar data obtained from images of the surface.

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Section: Free Surface Measurementsmentioning

confidence: 98%

Turbulence at Free Surface in Hydraulic Jumps

2004

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“…The spatial grid was defined with 0.03 m spacing in order to accurately characterize the large vortices structures inside the gully box ( Figure 3). The bottom of the grid is 0.05 m above the base of the gully box, which is well above the minimum (of 0.02 m) required to avoid boundary effects [22] and [23]. For reverse flow the first two columns away from the centre are displaced 0.04 from the centre and thus only 0.02 m from the next column.…”

Section: Experimental Methodologymentioning

confidence: 99%

Numerical and experimental characterization of the 2D vertical average-velocity plane at the center-profile and qualitative air entrainment inside a gully for drainage and reverse flow

et al. 2014

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“…Some discrepancies may also be caused by the use of discrete elements to represent the bed topography, which although they are very fine, cannot capture all of the bed details. Uncertainties in ADV measurements associated with the effects of turbulent structures smaller than the size of the sampling volume (Peltier et al, 2013) and increased noise in the vertical velocity component due to the presence of bubbles (Cea, Puertas, & Pena, 2007;Frizell, 2002;Liu, Zhu, & Rajaratnam, 2002) could have also introduced some errors.…”

Section: Flow Model Validationmentioning

confidence: 99%

Effects of Bed Forms and Large Protruding Grains on Near‐Bed Flow Hydraulics in Low Relative Submergence Conditions

2017

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In mountain rivers, bed forms, large relatively immobile grains, and bed texture and topographic variability can significantly alter local and reach‐averaged flow characteristics. The low relative submergence of large immobile grains causes highly three‐dimensional flow fields that may not be represented by traditional shear stress, flow velocity, and turbulence intensity equations. To explore the influence of large protruding grains and bed forms on flow properties, we conducted a set of experiments in which we varied the relative submergence while holding the sediment transport capacity and upstream sediment supply constant. Flow and bed measurements were conducted at the beginning and end of each experiment to account for the absence or presence of bed forms, respectively. Detailed information on the flow was obtained by combining our measurements with a 3‐D numerical model. Commonly used velocity profile equations only performed well at the reach scale when shallow flow effects and the roughness length of the relatively mobile sediment were considered. However, at the local scale large deviations from these profiles were observed and simple methods to estimate the spatial distribution of near‐bed shear stresses are likely to be inaccurate. Zones of high turbulent kinetic energy occurred near the water surface and were largely controlled by the immobile grains and plunging flow. The reach‐averaged shear stress did not correlate to depth or slope, as commonly assumed, but instead was controlled by the relative boulder submergence and degree of plunging flow. For accurate flow predictions in mountain rivers, the effects of bed forms and large boulders must be considered.

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Evaluation of ADV Measurements in Bubbly Two-Phase Flows

Cited by 30 publications

References 14 publications

Turbulence at Free Surface in Hydraulic Jumps

Turbulence at Free Surface in Hydraulic Jumps

Numerical and experimental characterization of the 2D vertical average-velocity plane at the center-profile and qualitative air entrainment inside a gully for drainage and reverse flow

Effects of Bed Forms and Large Protruding Grains on Near‐Bed Flow Hydraulics in Low Relative Submergence Conditions

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