scholarly journals A Modified Beam-to-Earth Transformation to Measure Short-Wavelength Internal Waves with an Acoustic Doppler Current Profiler

2005 ◽  
Vol 22 (5) ◽  
pp. 583-591 ◽  
Author(s):  
A. Scotti ◽  
B. Butman ◽  
R. C. Beardsley ◽  
P. Soupy Alexander ◽  
S. Anderson
Keyword(s):  
Internal Waves ◽  
Short Wavelength ◽  
Acoustic Doppler Current Profiler ◽  
Propagation Direction ◽  
Horizontal Distance ◽  
Massachusetts Bay ◽  
Backscatter Intensity ◽  
Current Profiler ◽  
Adcp Observations ◽  
Made In

Abstract The algorithm used to transform velocity signals from beam coordinates to earth coordinates in an acoustic Doppler current profiler (ADCP) relies on the assumption that the currents are uniform over the horizontal distance separating the beams. This condition may be violated by (nonlinear) internal waves, which can have wavelengths as small as 100–200 m. In this case, the standard algorithm combines velocities measured at different phases of a wave and produces horizontal velocities that increasingly differ from true velocities with distance from the ADCP. Observations made in Massachusetts Bay show that currents measured with a bottom-mounted upward-looking ADCP during periods when short-wavelength internal waves are present differ significantly from currents measured by point current meters, except very close to the instrument. These periods are flagged with high error velocities by the standard ADCP algorithm. In this paper measurements from the four spatially diverging beams and the backscatter intensity signal are used to calculate the propagation direction and celerity of the internal waves. Once this information is known, a modified beam-to-earth transformation that combines appropriately lagged beam measurements can be used to obtain current estimates in earth coordinates that compare well with pointwise measurements.

scholarly journals A Study of the Location of the Entrance of a Fishway in a Regulated River with CFD and ADCP

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Anders G. Andersson ◽  
Dan-Erik Lindberg ◽  
Elianne M. Lindmark ◽  
Kjell Leonardsson ◽  
Patrik Andreasson ◽  
...  
Keyword(s):  
Acoustic Doppler Current Profiler ◽  
Field Measurements ◽  
Fish Passage ◽  
Hydropower Plant ◽  
Regulated River ◽  
Unstable Flow ◽  
River Bed ◽  
Current Profiler ◽  
Tailrace Tunnel ◽  
Made In

Simulation-driven design with computational fluid dynamics has been used to evaluate the flow downstream of a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed, and the measurements were used to validate the simulations. The measurements indicate a more unstable flow than the simulations, and the tailrace jet from the turbines is stronger in the simulations. A fishway entrance was included in the simulations, and the subsequent attraction water was evaluated for two positions and two angles of the entrance at different turbine discharges. Results show that both positions are viable and that a position where the flow from the fishway does not have to compete with the flow from the power plant will generate superior attraction water. Simulations were also performed for further downstream where the flow from the turbines meets the old river bed which is the current fish passage for upstream migrating fish. A modification of the old river bed was made in the model as one scenario to generate better attraction water. This considerably increases the attraction water although it cannot compete with the flow from the tailrace tunnel.

scholarly journals Generation of Internal Waves by Eddies Impinging on the Western Boundary of the North Atlantic

2016 ◽  
Vol 46 (4) ◽  
pp. 1067-1079 ◽  
Author(s):  
L. Clément ◽  
E. Frajka-Williams ◽  
K. L. Sheen ◽  
J. A. Brearley ◽  
A. C. Naveira Garabato
Keyword(s):  
Internal Waves ◽  
North Atlantic ◽  
High Frequency ◽  
Large Scale ◽  
Acoustic Doppler Current Profiler ◽  
Relative Vorticity ◽  
Western Boundary ◽  
The North ◽  
Current Profiler ◽  
The North Atlantic

AbstractDespite the major role played by mesoscale eddies in redistributing the energy of the large-scale circulation, our understanding of their dissipation is still incomplete. This study investigates the generation of internal waves by decaying eddies in the North Atlantic western boundary. The eddy presence and decay are measured from the altimetric surface relative vorticity associated with an array of full-depth current meters extending ~100 km offshore at 26.5°N. In addition, internal waves are analyzed over a topographic rise from 2-yr high-frequency measurements of an acoustic Doppler current profiler (ADCP), which is located 13 km offshore in 600-m deep water. Despite an apparent polarity independence of the eddy decay observed from altimetric data, the flow in the deepest 100 m is enhanced for anticyclones (25.2 cm s−1) compared with cyclones (−4.7 cm s−1). Accordingly, the internal wave field is sensitive to this polarity-dependent deep velocity. This is apparent from the eddy-modulated enhanced dissipation rate, which is obtained from a finescale parameterization and exceeds 10−9 W kg−1 for near-bottom flows greater than 8 cm s−1. The present study underlines the importance of oceanic western boundaries for removing the energy of low-mode westward-propagating eddies to higher-mode internal waves.

Detecting plastic items in the water column using an Acoustic Doppler Current Profiler (ADCP)

2021 ◽  
Author(s):  
Frans Buschman ◽  
Sophie Broere
Keyword(s):  
Water Column ◽  
Acoustic Doppler Current Profiler ◽  
Signal Strength ◽  
Accurate Method ◽  
Background Signal ◽  
Detection Volume ◽  
Current Profiler ◽  
S Period ◽  
Adcp Observations ◽  
Feasibility Test

<p>An Acoustic Doppler Current Profiler (ADCP) is commonly used to monitor flow velocity. An accurate method to obtain discharge in a river or a channel is to mount an ADCP to a boat and sail transects across the channel. Additionally, these surveys may also be used to obtain the amount of plastic items in the water column. The transport of plastic items suspended in the water column may be substantial and is more challenging to monitor than the transport of floating items. We carried out a feasibility test in a harbour of a river. We deployed the ADCP horizontally at 1.0 m depth and released plastic items (and similarly shaped organic items for comparison) 5 times at 1.0, 3.0 and 5.0 m from the ADCP. We compared the signal strength in a 5 s period after release with the background signal strength.</p><p>The item was steady within the detection volume for the majority of the 5 s periods. Three out of five plastic items had signal strengths a least 5 dB higher than the background strength (at several distances). We conclude that at least these items were detected. The similarly shaped organic items generally had a lower signal strength. Although the response of each item as a function of orientation, distance along and across the beam should be investigated further, the feasibility study shows the potential to additionally determine the amount of plastic items in the water column from ADCP observations.  </p>

scholarly journals Internal-Wave Energy Fluxes on the New Jersey Shelf

2005 ◽  
Vol 35 (1) ◽  
pp. 3-12 ◽  
Author(s):  
Zachariah R. Hallock ◽  
Robert L. Field
Keyword(s):  
New Jersey ◽  
Internal Wave ◽  
Energy Flux ◽  
Vertical Component ◽  
Acoustic Doppler Current Profiler ◽  
Wave Mode ◽  
Buoyancy Frequency ◽  
Energy Fluxes ◽  
Current Profiler ◽  
Adcp Observations

Abstract Internal-wave energetics derived from moored acoustic Doppler current profiler (ADCP) observations on the New Jersey shelf are described. Horizontal and vertical velocity components from three 40-day ADCP records acquired near the shelf edge south of the Hudson Canyon were bandpass filtered to isolate high-frequency internal waves. In this band (0.5–7.5 h−1) the vertical component of velocity is significant and is integrated to yield elevation anomaly. Using the ADCP data with buoyancy frequency profiles from nearby CTD station data, kinetic energy (KE), baroclinic potential energy (PE), and energy flux were calculated. Results show depth-averaged KE and PE are nearly equal and of order 10−3 J kg−1, and there are significant northwestward fluxes, generally parallel to the bathymetry gradient, during most of the record, with depth-integrated magnitudes sometimes exceeding 100 W m−1. Vertical energy fluxes are small relative to horizontal fluxes. Vertical profiles of time-averaged flux suggest a dominant first internal-wave mode. Depth-integrated, time-averaged fluxes range from 9 to 24 W m−1, with the highest values occurring 18 km southwest of the Hudson Canyon. Two-dimensional probability density functions are estimated for energy flux. Group velocity of a large-amplitude internal-wave packet is estimated at 0.36 m s−1.

Klamath River Water Quality and Acoustic Doppler Current Profiler Data from Link River Dam to Keno Dam, 2007

2008 ◽  
Author(s):  
Annett B. Sullivan ◽  
Michael L. Deas ◽  
Jessica Asbill ◽  
Julie D. Kirshtein ◽  
Kenna D. Butler ◽  
...  
Keyword(s):  
Water Quality ◽  
River Water ◽  
Acoustic Doppler Current Profiler ◽  
River Water Quality ◽  
Klamath River ◽  
Current Profiler ◽  
Profiler Data
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