Acoustic density measurements of consolidating cohesive sediment beds by means of a non-intrusive “Micro-Chirp” acoustic system

Ha, Ho Kyung; Maa, Jerome P.‐Y.; Holland, Charles W.

doi:10.1007/s00367-010-0206-y

Cited by 7 publications

(3 citation statements)

References 28 publications

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“…This decreased sensitivity was also observed in the scattering cross-section results for flocculated calcite and may similarly indicate that, in modeling terms, a greater COV is measured by the ABS compared to the light scattering, when using the same mean number size. The form function data for flocculated calcite also support the scattering cross-section results, in that some degree of reduced scattering and attenuation is apparent for the flocs, compared to model data for a solid particle of the same size, in agreement with a number of previous results. ,,,, …”

Section: Resultssupporting

confidence: 86%

Characterizing Flocculated Mineral Sediments with Acoustic Backscatter, Using Solid and Hybrid Scattering Models

Tonge,

Peakall,

Lockwood

et al. 2023

Ind. Eng. Chem. Res.

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This study investigated the performance of an acoustic backscatter system (ABS) for the in situ particle characterization of complex wastes. Two sediments were used: a fine, milled calcite that was flocculated with anionic polyacrylamide and naturally flocculated pond sludge. Particles were initially measured independently by light-based techniques to gain size, the coefficient of variation (COV), and fractal dimensions. For acoustic experiments, a bespoke, high-fidelity ABS was employed with 1, 2.25, and 5 MHz probes and a recirculating mixing tank. Initially, the concentration independent attenuation and backscatter coefficients were measured for each system using a robust calibration procedure at multiple concentrations. Comparisons of the total scattering cross-section (χ) and form function (f) were made between the experimental data and two semiempirical models: a Solid Scattering model and a Hybrid model (where the effects of bound fluid are incorporated). Experimental data compared more closely to the Solid Scattering model, as it was assumed scattering was dominated by small, bound “flocculi” rather than the macroscopic structure. However, if the COV was used as a fit parameter, the hybrid model could give equally accurate fits for a range of input aggregate sizes, highlighting that important size and structure information can be gained from the acoustic models if there is some a priori system data. Additionally, dual-frequency inversions were undertaken to measure concentration profiles for various frequency pairs. Here, the lowest frequency pair gave the best performance (with accurate measurements in the range of 2–35 g·L–1) as interparticle scattering was lowest.

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Section: Resultssupporting

confidence: 86%

Characterizing Flocculated Mineral Sediments with Acoustic Backscatter, Using Solid and Hybrid Scattering Models

Tonge,

Peakall,

Lockwood

et al. 2023

Ind. Eng. Chem. Res.

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“…A step of 3.6 MHz leads to ∆d = 4.4 × 10 −3 g/cm 3 , i.e., a relative uncertainty well below 1%. This value makes the proposed sensor competitive with respect to acoustic sensors with the advantage of limiting the data treatment [35]. Note that the sensor displays such a high resolution due to the choice of the frequency range and to the optimization procedure detailed above.…”

Section: Vectorial Network Analyzermentioning

confidence: 99%

Development of a Resonant Microwave Sensor for Sediment Density Characterization

Mansour

Rioual

Lescop

et al. 2020

Sensors

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In this study, a sensor based on the development of a planar antenna immersed in sediments dedicated to water content monitoring in this type of material is proposed and experimentally validated. It is produced by a conventional Printed Circuit Board (PCB) manufacturing process on a double-sided metalized FR4 substrate. The sensitivity of the sensor is ensured by the variation of the real part of the complex dielectric permittivity of sediments with water content at around 1 GHz. As shown, in this frequency range, electrode polarization and Maxwell–Wagner polarization effects become negligible, leading to only a bulk water polarization sensitivity. The sensor operates in the reflection mode by monitoring the variation of the resonant frequency as a function of the sediment density through the S11 reflection measurements. An experimental sensitivity of 820 MHz . g − 1 . cm 3 was achieved. Despite the simplification of data interpretation at the considered frequency, the influence of ionic species such as NaCl in sediments on the real part of the relative complex dielectric permittivity is highlighted. This demonstrates the importance of considering a second parameter such as the S11 level at low frequency or the electrical conductivity to extract the density from the frequency measurements.

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“…structure and composition) remain a major challenge for improving understanding of sedimentation processes in mixed sedimentary environments (Ha et al 2010). The majority of sedimentation and consolidation studies are conducted in settling columns (te Slaa et al 2013), focussing on vertical profile measurements of bulk density development within the consolidating bed, as well as excess pore water pressure dissipation.…”

Section: Previous Work On Sand-mud Characterisation Techniquesmentioning

confidence: 99%

Monitoring and characterisation of sand-mud sedimentation processes

et al. 2016

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Estuaries and tidal inlets are often characterised by the presence of both cohesive and non-cohesive sediments. Knowledge of the sedimentation behaviour of sand-mud mixtures is therefore crucial to the understanding and prediction of the time-dependent structure (i.e. mixed or segregated), composition and erodibility of sediment bed deposits developing within these environments. In the current study, a series of settling column tests are conducted to investigate the hindered settling and initial bed consolidation phases of a range of sandclay mixtures to determine the parametric conditions under which bed segregation occurs. A new, non-invasive, electrical resistivity measurement technique is employed to capture both temporal and spatial changes in the density, porosity and composition of the evolving sand-clay bed deposits, complimented by time-lapsed images of the sedimentation process within the column. The results show that the formation of segregated (sand-clay) bed layers with bed deposits is largely controlled by the initial fractional composition (i.e. relative sand and clay concentrations). Specifically, mixtures with low clay contents are shown to form well-defined (sandclay) layer segregation within the resulting deposits, while higher clay contents result in more transitional segregation patterns or no layer segregation (for very high clay concentrations). The physical mechanisms under which these different segregation types can be generated are illustrated through predictions from an existing polydisperse hindered settling model. This model indicates that the degree of bed segregation, and time scale over which this occurs, correlates well with the difference in predicted hindered settling characteristics and upward displacements associated with the sand and clay fractions, respectively. In this regard, the new experimental dataset provides validation for the polydisperse model (for the first time), with the combined data and model predictions providing new insight into mixed (sand-clay) sedimentation processes.

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Acoustic density measurements of consolidating cohesive sediment beds by means of a non-intrusive “Micro-Chirp” acoustic system

Cited by 7 publications

References 28 publications

Characterizing Flocculated Mineral Sediments with Acoustic Backscatter, Using Solid and Hybrid Scattering Models

Characterizing Flocculated Mineral Sediments with Acoustic Backscatter, Using Solid and Hybrid Scattering Models

Development of a Resonant Microwave Sensor for Sediment Density Characterization

Monitoring and characterisation of sand-mud sedimentation processes

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