scholarly journals Analysis of acoustic Doppler current profiler mean velocity measurements in shallow flows

2020 ◽  
Vol 74 ◽  
pp. 101755
Author(s):  
Matthew R. Klema ◽  
Abdul G. Pirzado ◽  
S. Karan Venayagamoorthy ◽  
Timothy K. Gates
Keyword(s):  
Acoustic Doppler Current Profiler ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Shallow Flows ◽  
Current Profiler

scholarly journals Analysis of in situ water velocity distributions in the lowland river floodplain covered by grassland and reed marsh habitats - a case study of the bypass channel of Warta River (Western Poland)

2017 ◽  
Vol 65 (4) ◽  
pp. 325-332 ◽  
Author(s):  
Ireneusz Laks ◽  
Krzysztof Szoszkiewicz ◽  
Tomasz Kałuża
Keyword(s):  
Acoustic Doppler Current Profiler ◽  
Water Velocity ◽  
Concrete Slabs ◽  
Lowland River ◽  
Vegetation Types ◽  
Velocity Measurements ◽  
Flow Energy ◽  
Current Profiler

AbstractThe analysis of in situ measurements of velocity distribution in the floodplain of the lowland river has been carried out. The survey area was located on a bypass channel of the Warta River (West of Poland) which is filled with water only in case of flood waves. The floodplain is covered by grassland and reed marsh habitats. The velocity measurements were performed with an acoustic Doppler current profiler (ADCP) in a cross-section with a bed reinforced with concrete slabs. The measured velocities have reflected the differentiated impact of various vegetation types on the loss of water flow energy. The statistical analyses have proven a relationship between the local velocities and the type of plant communities.

Observations of Nepheloid Layers in the Yangtze Estuary, China, Through Phase-Corrupted Acoustic Doppler Current Profiler Speeds

2012 ◽  
Vol 46 (4) ◽  
pp. 60-70 ◽  
Author(s):  
Zhenyi Cao ◽  
Xiao Hua Wang ◽  
Weibing Guan ◽  
Les J. Hamilton ◽  
Qi Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Acoustic Doppler Current Profiler ◽  
Yangtze Estuary ◽  
Fluid Mud ◽  
Nepheloid Layer ◽  
The Yangtze Estuary ◽  
Mean Velocity ◽  
The North ◽  
Navigation Channel ◽  
Current Profiler

AbstractA bottom quadrapod was deployed from March 29 to April 5, 2009 to measure bottom boundary layer (BBL) flows and nepheloid layer properties in the Deepwater Navigation Channel in the North Passage of Shanghai Port in the Yangtze estuary. Using a downward-looking acoustic Doppler current profiler (ADCP) and acoustic Doppler velocimeter, detailed measurements of mean velocity and turbulence distribution within 1 m above the seabed were obtained. It appears that corrupted speeds measured for the deeper bins are caused by formation of the nepheloid layer at the seabed, implying that the ADCP is not a suitable instrument to measure current velocities in the bins nearest the seafloor. A statistical clustering method was used to characterize the current profiles in the BBL. The majority of current profiles within the BBL had a simple shape with current speed monotonically decreasing with depth, reflecting a logarithmic boundary layer. Phase-corrupted ADCP speeds measured for bins close to the bottom are shown to be useful as proxies to indicate the presence of primary and secondary lutoclines/nepheloid layers. A lutocline is a sediment-induced density gradient or pycnocline. The primary lutocline is closest to the bottom, and below it is the nepheloid layer, which is commonly composed of fluid mud. The proxies indicated that a nepheloid layer formed in the neap tide when the current velocity 1 m above the seabed dropped below a threshold of 0.65 m/s. The lutocline height was indicated to be about 0.2 m above the seabed. A secondary lutocline in the water column was also observed in the second half of the record, when the lowest maximum currents occurred.

scholarly journals The Finescale Response of Lowered ADCP Velocity Measurements Processed with Different Methods

2012 ◽  
Vol 29 (4) ◽  
pp. 597-600 ◽  
Author(s):  
A. M. Thurnherr
Keyword(s):  
Acoustic Doppler Current Profiler ◽  
Processing Method ◽  
Vertical Shear ◽  
Inversion Method ◽  
Velocity Data ◽  
Velocity Measurements ◽  
Processing Methods ◽  
Velocity Inversion ◽  
Current Profiler ◽  
Specific Implementation

Abstract In a paper published in 2002 in this journal, K. Polzin et al. derive corrections for spectra of vertical shear calculated from lowered acoustic Doppler current profiler (LADCP) velocity data. To illustrate and validate the corrections, they use velocities derived with a specific implementation of the shear method for LADCP processing that is no longer supported or widely used. In several recent publications, spectral corrections specific to this old processing method have been applied without modification to LADCP data processed with the more modern and much more widely used velocity-inversion method, which is associated with significantly less damping at high vertical wavenumbers than the older method. The purpose of this work is to derive and validate spectral corrections appropriate for different LADCP processing methods.

Measurements of Tidal Current Velocities in the Folda Fjord, Norway, With the Use of a Vessel Mounted ADCP

2014 ◽  
Author(s):  
Nicole Carpman ◽  
Mats Leijon
Keyword(s):  
Tidal Current ◽  
Energy Resource ◽  
Acoustic Doppler Current Profiler ◽  
Renewable Energy Resource ◽  
Mean Velocity ◽  
Average Width ◽  
First Approximation ◽  
Current Profiler ◽  
Current Water ◽  
Mean Current

Measurements of tidal current water velocities is an important first step in evaluating the potential for a tidal site to be used as a renewable energy resource. For this reason, on site measurements are performed at the inlet of a fjord situated at the coast of Norway. The site has an average width of 580 m and a depth of 10–15 m which is narrow and shallow enough to give rise to water velocities that can be of use for energy conversion. With the use of an Acoustic Doppler Current Profiler (ADCP) cross-section measurements are conducted along four transects. The measurements covered flood and ebb currents around one tide and the data give a first approximation of the magnitude and distribution of the flow field. Depth averaged mean current velocities are calculated along the transects for horizontal bins with sizes in the order of 50 × 50 m. Maximum mean velocity for the flood currents were 1.31 m/s and 1.46 m/s for the ebb currents. The measurements show that even a small amount of data can give an indication of the potential and characteristics of the site.

scholarly journals Using Orthogonal Combined Signals in Broadband ADCP for Improving Velocity Measurement

2020 ◽  
Vol 8 (6) ◽  
pp. 450
Author(s):  
Yujing Lin ◽  
Fei Yuan ◽  
En Cheng
Keyword(s):  
Current Velocity ◽  
Velocity Measurement ◽  
Water Environment ◽  
Acoustic Doppler Current Profiler ◽  
Processing Method ◽  
Velocity Measurements ◽  
Signal Parameters ◽  
Current Profiler ◽  
Signal Combination ◽  
Conventional Signal

Broadband Acoustic Doppler Current Profiler (BBADCP) is a widely used technology in velocity measurements. To adapt to the varied water environment and different measurement requirements, flexible tuning of transmitted signal parameters will improve the feasibility and accuracy of velocity measurement. Compared with the conventional signal, the orthogonal combined signal designed in this paper can generate a wealth of signal combination examples and improve the accuracy of the velocity measurement under the same conditions. The proposed orthogonal combined signal consists of two orthogonal sub-signals with a symmetrical spectrum. Each is designed based on time delay to eliminate or weaken the current velocity ambiguity. Then, the processing method of the received signal when the pulse signals are the same or different coded signal is discussed. The numerical simulation results show that, when using the proposed method, the standard deviation of the estimated current velocity has different degrees of reduction at different current velocities. Our simulation also shows that, compared to the convention method, the proposed method can improve the SNR by 10 dB. This can help significantly increase the scope of the configuration.

scholarly journals Removing Wave Bias from Velocity Measurements for Tracer Transport: The Harmonic Analysis Approach

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1138 ◽  
Author(s):  
Sangdon So ◽  
Arnoldo Valle-Levinson ◽  
Jorge Armando Laurel-Castillo ◽  
Junyong Ahn ◽  
Mohammad Al-Khaldi
Keyword(s):  
Harmonic Analysis ◽  
Gravity Wave ◽  
Wave Energy ◽  
Acoustic Doppler Current Profiler ◽  
Surface Gravity ◽  
Tracer Transport ◽  
Velocity Measurements ◽  
Surface Gravity Wave ◽  
Current Profiler ◽  
Adcp Measurements

Estimates of turbulence properties with Acoustic Doppler Current Profiler (ADCP) measurements can be muddled by the influence of wave orbital velocities. Previous methods—Variance Fit, Vertical Adaptive Filtering (VAF), and Cospectra Fit (CF)—have tried to eliminate wave-induced contamination. However, those methods may not perform well in relatively energetic surface gravity wave or internal wave conditions. The Harmonic Analysis (HA) method proposed here uses power spectral density to identify waves and least squares fits to reconstruct the identified wave signals in current velocity measurements. Then, those reconstructed wave signals are eliminated from the original measurements. Datasets from the northeastern Gulf of Mexico and Cape Canaveral, Florida, are used to test this approach and compare it with the VAF method. Reynolds stress estimates from the HA method agree with the VAF method in the lower half of the water column because wave energy decays with depth. The HA method performs better than the VAF method near the surface during pulses of increased surface gravity wave energy.

Sign in / Sign up

Export Citation Format

Share Document