Effect of clay content on Acoustic Doppler Velocimeter backscatter for suspended sediment concentration measurements

2021 ◽  
Author(s):  
Akın Aras ◽  
Cihan Sahin
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Experimental Studies ◽  
Clay Content ◽  
Sediment Concentration ◽  
Acoustic Backscatter ◽  
Doppler Velocity ◽  
Clay Material ◽  
Sediment Distribution ◽  
Wide Range

<p>The capability of ADVs (Acoustic Doppler Velocimeters) to estimate suspended sediment concentration (SSC) has been widely investigated using commercial glass microspheres of the same size or well-sorted fractions in experimental studies. In the natural environment, sediment samples may be composed of different types of sediments having various types of grain size distribution.</p><p>This study aims to analyze experimentally the effect of clay ratio in sediment content on acoustic response. Modification of scattering and attenuation characteristics for different clay ratios is evaluated theoretically. In laboratory experiments, four different sediment mixtures constituting non-cohesive sand and cohesive clay materials were prepared with clay ratios of 0, 5, 10 and 15% by dry mass. A-10 MHz acoustic Doppler velocity profiler (ADVP, The Nortek Vectrino Profiler) was used in controlled laboratory environments under a wide range of concentration conditions up to 10 g/L. Acoustic backscatter measurements were made by immersing the ADVP in a well-mixed circulation tank filled with mixtures with known concentration and sediment composition. The backscattered signals were recorded at 100 Hz, from which 1.5-min ensemble averages were obtained. For each sediment mixture, calibration curves representing the relationship between SSC and acoustic backscatter were obtained based on the sonar equation. Acoustic estimates of suspended sediment parameters obtained for mixtures with different clay contents are compared to identify the effect of increasing clay content on the acoustic signal.</p><p>The experimental results showed that the slope of the calibration curve decreases with increasing validity range as the clay ratio of the mixture increases. Under the fixed SSC condition, the backscatter strength is greater for the mixture with a lower clay ratio. The theoretical analysis indicated that changing clay content modifies the scattering and attenuation properties compared to the mono-size suspension with the same mean size. Introducing clay material in a mixture affects the scattering properties more significantly than the attenuation properties. Therefore, information on the form of the sediment distribution and the sorting of sediments in suspension is crucial for acoustic estimates of suspended sediment parameters.</p><p>Acknowledgments</p><p>This research is supported by the Scientific and Technological Research Council of Turkey (TUBITAK) with project number 218M428.</p>

Research on the Coastal Suspended Sediment Movement of Matakong Island in Guinea, Africa Based on Remote Sensing Data

2013 ◽  
Vol 333-335 ◽  
pp. 275-279
Author(s):  
Yin Cai ◽  
Hong Bo Zhao ◽  
Shu Hua Zuo
Keyword(s):  
Remote Sensing ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Remote Sensing Data ◽  
Sediment Concentration ◽  
Concentration Data ◽  
Sediment Distribution ◽  
Sensing Data ◽  
Sediment Movement ◽  
Wide Range

A wide range of suspended sediment concentration can be obtained by satellite remote sensing. According to the multi-temporal remote sensing data and quasi-simultaneously surface sediment concentration data, research works on the surface suspended sediment distribution and movement trends of Matakong coastal area, Africa were carried out. The results showed that the suspended sediment concentration of the studied area is not large, and the sediment movement is not active. The sediment source comes from the nearshore shallow flats, where they could be entrained by the wind waves and then diffuses by the tidal currents.

Acoustic Inversion Method for Profiling Suspended Sediment Concentration

2014 ◽  
Vol 687-691 ◽  
pp. 3980-3983
Author(s):  
Jun Xi Shi ◽  
Min Zhu ◽  
Yan Bo Wu ◽  
Xing Tao Sun
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Acoustic Backscatter ◽  
Inversion Method ◽  
Dual Frequency ◽  
Frequency Method ◽  
Backscatter Signal ◽  
Size Profile ◽  
Acoustic Inversion

The concentration of suspended sediment is an important parameter for the research of sediment transport. Acoustic backscatter technique has been employed to measure the concentration of suspended sediment recently. It is an inversion problem to measure the concentration from the backscatter signal. In this paper, an improved dual-frequency method is proposed for the concentration inversion of suspension sediment. It is an explicit solution with much lower computational complexity than the commonly used iterative method and with no requirement of known and constant particle size profile compared to the basic dual-frequency method.

scholarly journals COUPLED WAVE-BED DYNAMICS, ATCHAFALAYA SHELF, LOUISIANA

2012 ◽  
Vol 1 (33) ◽  
pp. 116
Author(s):  
Cihan Sahin ◽  
Ilgar Safak ◽  
Alexandru Sheremet
Keyword(s):  
Shear Stress ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Critical Shear Stress ◽  
Flow Characteristics ◽  
Sediment Concentration ◽  
Density Variation ◽  
Acoustic Backscatter ◽  
Concentration Profiles ◽  
Fluid Mud

Observations of waves, currents, suspended sediment concentration and acoustic backscatter are used to re-investigate the interaction between the combined wave-current flow and cohesive sediments on the muddy Atchafalaya inner shelf. Observations support the previously proposed bed reworking cycle by waves of mobilization and resuspension of bed sediment, erosion, deposition with fluid mud formation and consolidation. Suspended sediment concentration profiles are estimated based on the acoustic backscatter of a current profiler. A one-dimensional vertical bottom boundary model is used to reconstruct the vertical structure of the flow characteristics, and estimate parameters difficult to observe directly, such as bottom shear stress. Estimated bed position, concentration profiles and computed bottom stresses remarkably support the previous findings on the bottom stress-resuspension relation, critical shear stress for erosion and bed density variation throughout a storm.

scholarly journals USE OF DIGITAL HOLOGRAPHIC CAMERAS TO EXAMINE THE MEASUREMENT AND UNDERSTANDING OF SEDIMENT SUSPENSION IN THE NEARSHORE

2012 ◽  
Vol 1 (33) ◽  
pp. 73
Author(s):  
Daniel Conley ◽  
Daniel Buscombe ◽  
Alex Nimmo-Smith
Keyword(s):  
Size Distribution ◽  
Suspended Sediment ◽  
Surf Zone ◽  
Sediment Concentration ◽  
Acoustic Backscatter ◽  
Sediment Suspension ◽  
Data Set ◽  
Sediment Grain Size ◽  
Grain Sizes ◽  
Wide Range

We present results from a 3-week field experiment measuring surf-zone flows and sediment transport on a steep energetic beach in the south-west UK, including the first reported deployment of an in-line holographic camera (‘holocam’) in the surf zone, co-located with various optical backscatter sensors and an acoustic backscatter sensor (ABS). The extensive data set provides perhaps a unique opportunity to examine the performance of optical and acoustic backscatter instruments in a wide range of conditions including bubbly flows, as well as some fundamental aspects of sediment suspension processes such as the near-bed size-distribution of suspended sediment. The holocam, deployed with a 1.3cm cubic sample volume approximately 10cm above the bed, provides in-focus well-resolved images of the instantaneous suspended load, making it possible to determine highly-accurate estimates of the concentrations of mineral sand grains, bubbles and organic particles, and their size distributions. Instantaneous estimates of sediment concentration from the ABS compare poorly with the equivalent measure from the holocam. This could be due to various factors such as spatial decorrelation or acoustic insensitivities at larger grain sizes. However, the ABS does a very good job at estimating burst-averaged suspended sediment concentrations when bubble concentrations are low (less than 1ml/l). The error in ABS concentrations (as compared against holocam) appears to be related to relative bubble concentration. The OBS is even more sensitive to bubbles. Suspended sediment grain size distribution is skewed towards the finer grain sizes but shifts to the larger sizes with increased flow intensity.

scholarly journals Investigating Suspended-Sediment Transport in a Shallow Lake Using a Three-Dimensional Model

2017 ◽  
Author(s):  
Hong-Ming Liu ◽  
Wen-cheng Liu ◽  
Chih-Yu Chiu
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Shallow Lake ◽  
Suspended Sediment Concentration ◽  
Transport Model ◽  
Three Dimensional ◽  
Sediment Concentration ◽  
Suspended Sediment Transport ◽  
Sediment Distribution ◽  
Mean Current

A three-dimensional, unstructured grid, hydrodynamic and suspended-sediment transport model (i.e., SELFE-SED) was developed to simulate temporal and spatial variations of suspended sediment and was applied to the subtropical subalpine Tsuei-Feng Lake (TFL) of Taiwan. The model was validated with measured water level and suspended‑sediment concentration in 2009, 2010, and 2011. The overall model simulation results are in quantitative agreement with the observational data. The validated model was then applied to explore the most important parameter that affects the suspended-sediment concentration and to investigate the effect of wind stress on the mean current and suspended‑sediment distribution in this shallow lake. Modeling results of sensitivity analysis reveal that the settling velocity is a crucial parameter and erosion rate is less important in the suspended-sediment transport model. Remarkable lake circulation was found based on the strength of wind speed and wind direction. Strong wind would result in higher mean current in the top layer and suspended-sediment distribution in the top and bottom layers. This study demonstrated that the wind stress played a significant influence on mean circulation and suspended-sediment transport in a shallow lake.

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