Performance of a single-beam pulse-to-pulse coherent Doppler profiler

Zedel, Len; Hay, Alex E.; Cabrera, R.; Lohrmann, Atle

doi:10.1109/48.508159

Cited by 125 publications

(95 citation statements)

References 9 publications

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“…High-resolution three-dimensional acoustic Doppler velocity profiler (3D ADVP) Three-dimensional turbulent velocity profiles were measured along a vertical line over the range 0.02 < z/δ < 0.95 using an acoustic Doppler velocity profiler (ADVP). This type of instrument and its use in measuring turbulent flows are discussed by Garbini, Forster & Jorgensen (1982), Lhermitte & Lemmin (1994), Zedel et al (1996), Hurther & Lemmin (1998 and Blanckaert & deVriend (2004, 2005. A schematic of the instrument is shown in figure 1.…”

Section: Experimental Set-upmentioning

confidence: 99%

Turbulent transport in the outer region of rough-wall open-channel flows: the contribution of large coherent shear stress structures (LC3S)

2007

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Acoustic Doppler velocity profiler (ADVP) measurements of instantaneous threedimensional velocity profiles over the entire turbulent boundary layer height, δ, of rough-bed open-channel flows at moderate Reynolds numbers show the presence of large scale coherent shear stress structures (called LC3S herein) in the zones of uniformly retarded streamwise momentum. LC3S events over streamwise distances of several boundary layer thicknesses dominate the mean shear dynamics. Polymodal histograms of short streamwise velocity samples confirm the subdivision of uniform streamwise momentum into three zones also observed by Adrian et al. (J. Fluid Mech., vol. 422, 2000, p. 1). The mean streamwise dimension of the zones varies between 1δ and 2.5δ. In the intermediate region (0.2 < z/δ < 0.75), the contribution of conditionally sampled u w events to the mean vertical turbulent kinetic energy (TKE) flux as a function of threshold level H is found to be generated by LC3S events above a critical threshold level H max for which the ascendant net momentum flux between LC3S of ejection and sweep types is maximal. The vertical profile of H max is nearly constant over the intermediate region, with a value of 5 independent of the flow conditions. Very good agreement is found for all flow conditions including the free-stream shear flows studied in Adrian et al. (2000). If normalized by the squared bed friction velocity, the ascendant net momentum flux containing 90 % of the mean TKE flux is equal to 20 % of the shear stress due to bed friction. In the intermediate region this value is nearly constant for all flow conditions investigated herein. It can be deduced that free-surface turbulence in open-channel flows originates from processes driven by LC3S, associated with the zonal organization of streamwise momentum. The good agreement with mean quadrant distribution results in the literature implies that LC3S identified in this study are common features in the outer region of shear flows.

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Section: Experimental Set-upmentioning

confidence: 99%

Turbulent transport in the outer region of rough-wall open-channel flows: the contribution of large coherent shear stress structures (LC3S)

2007

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“…The short pulses provide high spatial resolution, while the interval between the pulses provides low noise by permitting time for movement of scatterers, yielding substantial phase shifts. However, there is an inherent limitation on the product of the profiling range and the unambiguous velocity that can be resolved, i.e., the faster the flow, the shorter the range than can be profiled (Lhermitte and Serafin 1984;Lohrmann et al 1990;Zedel et al 1996).…”

Section: Materials and Proceduresmentioning

confidence: 99%

A novel drifter designed for use with a mounted Acoustic Doppler Current Profiler in shallow environments

Mullarney

Henderson

2013

Limnology & Ocean Methods

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Lagrangian drifters have been used for many years to measure surface currents over a wide range of spatial and temporal scales. The cost and design of these drifters varies depending on the application. Building on deployments of drifters in the deep ocean (e.g., Davis 1985), and taking advantage of cheap and accurate modern GPS systems, researchers have recently developed low-cost drifters for use in nearshore, estuarine (Johnson et al. 2003;Austin and Atkinson 2004;Thomson 2012) and surfzone (Schmidt et al. 2003;MacMahan et al. 2009) environments. However, the drifter designs above typically have drafts of around 0.5 to 1 m, rendering them unsuitable for use in very shallow flows.Modern compact Acoustic Doppler Current Profilers (ADCPs) are capable of measuring velocities over range bins of a few centimeters. The small size, high resolution, and short blanking distance of these instruments have raised the possibility of using drifter-mounted ADCPs to resolve near-surface flows, even in very shallow environments.We present a novel design for surface drifters intended for use with a Nortek Aquadopp ADCP. The design yielded highresolution vertical profiles of velocity, as the drifter tracked the propagation of baroclinic surface fronts over very shallow tidal flats (water depths of 0.2-1 m). The highest bin of the velocity profiles was around just 0.18 m below the water surface, a notable improvement over use of majority of the above designs, which would result in a smallest measurement depth of around 0.62 m below the surface (based on a representative 0.5 m drifter draft plus 0.07 m ADCP draft plus 0.05 m blanking distance). The Thomson (2012) drifter used an uplooking ADCP, which allowed measurements to be made close to the water surface; however, the drifter had a 1.25 m draft preventing its deployment in very shallow water depths. For water depths of between 0.15 m and 0.18 m, the ADCP-mounted drifter described here was still freely advected, but in this case, ADCP measurements were not obtained. The drifters were robust and of very simple construction, requiring only use of hand tools and using off-the-shelf components. Although the cost of the ADCP was substantial (exceeding US$10,000), the cost for each drifter body was minimal (less than US$100, similar to costs of the other drifters above). Drifter positions were tracked by an inexpensive off-the-shelf GPS logger (

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“…Two output parameters computed by the NDV were used to monitor the quality of the data: correlation and signal-tonoise ratio (SNR). The first refers to the correlation coefficient between successive velocity estimates from each receiver (Zedel et al 1996). SNR is calculated using the signal amplitude and background noise amplitudes (McLelland and Nicholas 2000).…”

Section: Guadayol Et Al Turbulence In Laboratory Containersmentioning

confidence: 99%

Evaluation of oscillating grids and orbital shakers as means to generate isotropic and homogeneous small‐scale turbulence in laboratory enclosures commonly used in plankton studies

Guadayol

Peters

Stiansen

et al. 2009

Limnology & Ocean Methods

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The effects of turbulent motion on planktonic organisms have mainly been studied in the laboratory with devices capable of generating controlled turbulent conditions. Owing to technical and logistical difficulties, thorough assessments of hydrodynamics in such experiments are not routinely made. In this study, we examined the suitability of two widely used systems to generate isotropic, homogeneous, and stationary turbulence in laboratory containers: oscillating grid devices with large stroke length and relatively low frequencies of oscillation and orbital shaker tables. Turbulent kinetic energy dissipation rates were estimated from velocity measurements made with acoustic Doppler velocimeters. Both systems were shown to generate isotropic conditions in a relatively broad range of dissipation rates. Grid-stirred tanks produce homogeneous turbulence in both the horizontal and vertical dimensions, as long as stroke length is comparable to the height of the container. Turbulence in orbital shakers is not completely homogeneous, as it depends on the distance to the wall and to the surface. Empirical models are derived as a tool for the calculation of dissipation rates in the two systems within the ranges and conditions examined in this study.

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Performance of a single-beam pulse-to-pulse coherent Doppler profiler

Cited by 125 publications

References 9 publications

Turbulent transport in the outer region of rough-wall open-channel flows: the contribution of large coherent shear stress structures (LC3S)

Turbulent transport in the outer region of rough-wall open-channel flows: the contribution of large coherent shear stress structures (LC3S)

A novel drifter designed for use with a mounted Acoustic Doppler Current Profiler in shallow environments

Evaluation of oscillating grids and orbital shakers as means to generate isotropic and homogeneous small‐scale turbulence in laboratory enclosures commonly used in plankton studies

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