Dynamic response of thin‐wire wave gauges

Liu, H.-T.; Katsaros, Kristina B.; Weissman, Michael A.

doi:10.1029/jc087ic08p05686

Cited by 18 publications

(12 citation statements)

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“…Previous studies were mainly performed with Pitot tubes and conductivity probes (Chanson,[3]), Laser Doppler Velocimetry (Waniewski et al, [4]), or Acoustic Doppler Velocimetry (Liu et al, [5]). Intrusive probes clearly suffer the disadvantage that they could affect the flow, but the nonintrusive techniques (LDV and ADV) also face strong technical limitations in such aerated conditions.…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

Turbulence at Free Surface in Hydraulic Jumps

2004

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“…Typically heights vary between 0.3 to 1 m with a rod diameter of 3 to 4 mm [68], but thinner wire can be utilised if necessary. Andresen and Frigaard [69] applied wave gauges made of a wire with 1 mm near a cylinder under wave conditions and even thinner, namely 0.13 and 0.4 mm, are used by Liu et al [70] in a wind-wave tank.…”

Section: Copper Tape Resistive Wave Gaugesmentioning

confidence: 99%

Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure

Gabl

Steynor

Forehand

et al. 2018

Water

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Large floating structures, such as liquefied natural gas (LNG) ships, are subject to both internal and external fluid forces. The internal fluid forces may also be detrimental to a vessel’s stability and cause excessive loading regimes when sloshing occurs. Whilst it is relatively easy to measure the motion of external free surface with conventional measurement techniques, the sloshing of the internal free surface is more difficult to capture. The location of the internal free surface is normally extrapolated from measuring the pressure acting on the internal walls of the vessel. In order to understand better the loading mechanisms of sloshing internal fluids, a method of capturing the transient inner free surface motion with negligible affect on the response of the fluid or structure is required. In this paper two methods will be demonstrated for this purpose. The first approach uses resistive wave gauges made of copper tape to quantify the water run-up height on the walls of the structure. The second approach extends the conventional use of optical motion tracking to report the position of randomly distributed free floating markers on the internal water surface. The methods simultaneously report the position of the internal free surface with good agreement under static conditions, with absolute variation in the measured water level of around 4 mm. This new combined approach provides a map of the free surface elevation under transient conditions. The experimental error is shown to be acceptable (low mm-range), proving that these experimental techniques are robust free surface tracking methods in a range of situations.

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“…where E'(f) is the measured spectral energy density and E(f) is the corrected value. The exponent p depends on the diameter of the wire used, and for 0.13 mm it is approximately unity [Liu et al, 1982]. (We are assuming that the laboratory calibration also applies to the field conditions.…”

Section: E(f) = E'(f)(f/fo) P (1)mentioning

confidence: 99%

“…In that report, agreement between the two methods was achieved after an empirical correction was applied to the wire gauge data. However, the correction currently being used differs from that reported by Liu et al [1982] by a constant (owing to an error in the calibration of the wire gauge) and is defined for frequencies above f0 (= 10 Hz)as…”

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confidence: 98%

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Intrinsic frequency spectra of short gravity‐capillary waves obtained from temporal measurements of wave height on a lake

Atakturk

Katsaros

1987

J. Geophys. Res.

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Intrinsic frequency spectra of water waves in the range of 6-17 Hz were obtained as a function of both wind speed and wind stress from point measurements of wave height. In a lake with a limited fetch there are two types of surface motions causing Doppler shift in the frequencies of short waves: orbital velocity of long waves and surface wind drift. The former was estimated from long-wave amplitude by using a linear wave theory. The error in this estimate is of the order of the long-wave slope, and for this work it is typically 10%. The latter was approximated by the friction velocity. The friction velocity could be either taken as 3% of the mean wind speed measured at a height of 10 m or obtained from our direct measurements of the wind stress. The surface drift velocities obtained by these two approaches were found to be in close agreement. However, the estimate based on the mean wind speed was preferred because of its simplicity. Doppler frequency shift can be corrected in either the frequency or the equivalent spatial domain. A comparison of these techniques from both a theoretical and a practical point of view was made. The two techniques were found to produce comparable results. Experimental results showed that the spectral energy of short waves rapidly increased in response to increasing winds and jumped up by an order of magnitude when wave breaking occurred. INTRODUCTION The transfer of wind energy and momentum to the sea involves water surface waves of different length scales. The short gravity-capillary waves provide the roughness elements with which the wind interacts [Stewart, 1961]. The longer waves cause the wave-induced pressure fluctuations which are central to the energy flux from wind to waves (see, for example, Phillips [1977, p. 132]). The relative importance of these two stress transfer mechanisms is thought to be a function of the mean wind stress itself, but the details are poorly known [e.g., Valenzuela, 1976; Plant and Wri#ht, 1977; Snyder et al., 1981; Mitsuyasu, 1985]. The relation of the amplitude of these smallscale waves to wind speed or stress and their dependence on the presence of longer waves or mean currents have also become increasingly important from a technological point of view. This has occurred because the remote sensing techniques used to infer these other phenomena depend on the resonant interaction of the electromagnetic radiation with the smallscale surface waves (Bragg scatter). The electromagnetic theory for Bragg scattering is evidently well understood [Rice, 1951; Wright, 1968; Brown, 1978; Ulaby et al., 1981; Keller et al., 1985]. However, whether the scatterometer signal is proportional to wind speed or wind stress is a fundamental question of importance to many investigations which involve scatterometer data. (For discussions, see, for instance, O'Brien et al. [1982], Brown [1983, 1986], Pierson [1983], and Donelan and Pierson [1984].) Other features of the sea surface related to wave breaking may also contribute to the radar backscatter [Keller et al., 1986; B...

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Dynamic response of thin‐wire wave gauges

Cited by 18 publications

References 11 publications

Turbulence at Free Surface in Hydraulic Jumps

Turbulence at Free Surface in Hydraulic Jumps

Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure

Intrinsic frequency spectra of short gravity‐capillary waves obtained from temporal measurements of wave height on a lake

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