Ultrasonic characterization of marine sediments: a preliminary study

Maa, Jerome P.‐Y.; Sun, K.J.; He, Qing

doi:10.1016/s0025-3227(97)00078-9

Cited by 17 publications

(4 citation statements)

References 11 publications

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“…An ADV was utilized to measure bed‐level changes, not only due to its high accuracy (±1 mm) (e.g., Andersen et al, ; Salehi & Strom, ; Shi et al, ), but also because it is able to detect the interface between the water mass and sediment bed. ADV is based on acoustic rather than optical principles (e.g., Lohrmann et al, ; Maa et al, ; Poindexter et al, ; Shi et al, ; Voulgaris & Trowbridge, ) and, unlike optical instruments, ADV measurements of bed levels are not affected by near‐bed fluid‐like mud. For example, in January and November 2005 on the Kongsmark mudflat in the Lister Dyb tidal basin, Danish Wadden Sea, Andersen et al () have measured the time‐series of bed‐level changes in the presence of maximum SSC values as high as 2.5 − 3.0 kg/m 3 (Figures and in the Andersen et al ()), which is similar to most of SSC values at the present study site (Figure b), suggesting that ADV bed‐level instrument could be insensitive to the impact of high SSCs.…”

Section: Discussionmentioning

confidence: 99%

Erosion and Accretion on a Mudflat: The Importance of Very Shallow‐Water Effects

et al. 2017

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Understanding erosion and accretion dynamics during an entire tidal cycle is important for assessing their impacts on the habitats of biological communities and the long‐term morphological evolution of intertidal mudflats. However, previous studies often omitted erosion and accretion during very shallow‐water stages (VSWS, water depths < 0.20 m). It is during these VSWS that bottom friction becomes relatively strong and thus erosion and accretion dynamics are likely to differ from those during deeper flows. In this study, we examine the contribution of very shallow‐water effects to erosion and accretion of the entire tidal cycle, based on measured and modeled time‐series of bed‐level changes. Our field experiments revealed that the VSWS accounted for only 11% of the duration of the entire tidal cycle, but erosion and accretion during these stages accounted for 35% of the bed‐level changes of the entire tidal cycle. Predicted cumulative bed‐level changes agree much better with measured results when the entire tidal cycle is modeled than when only the conditions at water depths of >0.2 m (i.e., probe submerged) are considered. These findings suggest that the magnitude of bed‐level changes during VSWS should not be neglected when modeling morphodynamic processes. Our results are useful in understanding the mechanisms of micro‐topography formation and destruction that often occur at VSWS, and also improve our understanding and modeling ability of coastal morphological changes.

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Section: Discussionmentioning

confidence: 99%

Erosion and Accretion on a Mudflat: The Importance of Very Shallow‐Water Effects

et al. 2017

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“…Values in different suspensions, e.g. kaolin clay slurries [31], clay sediments [32,33], cornstarch [34], glass [35], were therefore examined to find a convenient one. In the weight range of 1-5%, the differences in sound speed may be ignored and the values are almost equal to that in water (1496 m/s at 25°C) which was consequently used for the calculation.…”

Section: Ultrasound Applicationmentioning

confidence: 99%

Optimization of hydrostatic pressure at varied sonication conditions – power density, intensity, very low frequency – for isothermal ultrasonic sludge treatment

Delmas

Barthe

et al. 2015

Ultrasonics Sonochemistry

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This work aims at investigating for the first time the key sonication (US) parameters: power density (DUS), intensity (IUS), and frequency (FS) - down to audible range, under varied hydrostatic pressure (Ph) and low temperature isothermal conditions (to avoid any thermal effect). The selected application was activated sludge disintegration, a major industrial US process. For a rational approach all comparisons were made at same specific energy input (ES, US energy per solid weight) which is also the relevant economic criterion. The decoupling of power density and intensity was obtained by either changing the sludge volume or most often by changing probe diameter, all other characteristics being unchanged. Comprehensive results were obtained by varying the hydrostatic pressure at given power density and intensity. In all cases marked maxima of sludge disintegration appeared at optimum pressures, which values increased at increasing power intensity and density. Such optimum was expected due to opposite effects of increasing hydrostatic pressure: higher cavitation threshold then smaller and fewer bubbles, but higher temperature and pressure at the end of collapse. In addition the first attempt to lower US frequency down to audible range was very successful: at any operation condition (DUS, IUS, Ph, sludge concentration and type) higher sludge disintegration was obtained at 12 kHz than at 20 kHz. The same values of optimum pressure were observed at 12 and 20 kHz. At same energy consumption the best conditions - obtained at 12 kHz, maximum power density 720 W/L and 3.25 bar - provided about 100% improvement with respect to usual conditions (1 bar, 20 kHz). Important energy savings and equipment size reduction may then be expected.

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“…Therefore, clays can affect the electrical balance of sediment absorbing water and changing the degree of sediment consolidation (Hamilton 1970). Thus, on fine grain cores (BCCF10-04 and BCCF10-09) P-wave propagation tend to slow down ( Figure 6), due to the increase of water content and low elastic compression of the sediment (Maa et al 1997).…”

Section: Core Bccf10-13mentioning

confidence: 99%

Physical and geochemical properties of centennial marine sediments of the continental shelf of southeast Brazil

Cruz

Barbosa²,

Ayres-Neto³

et al. 2013

Geochim. Bras.

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Studies associated with the physical properties of marine sediments are being increasingly disseminated around the world. Comparing these geophysical parameters with sedimentological analysis allows several correlations of the core collected in a region. This research combines sedimentological information of cores samples with geophysical and geochemical properties to identify the influence of organic matter and sediment texture on the characteristics and depositional dynamic. The sediment cores were collected using a box core in four stations of the mud facies from the Cabo Frio shelf, Brazil. Geophysical properties were acquired using the MSCL (multi-sensor core logger). The wave velocity, porosity, density, sediment texture, and organic content have been conducted in samples collected in the shelf mud. The physical properties helped to distinguish two groups, according to oceanographic and sedimentological patterns within the same depositional system. The first group was characterized by the presence of silty sand and high P-wave velocity (nearshore and offshore core) and the second group by the predominance of silt, high organic input, and porosity (the intermediate cores). The presence of coarser sediments in the first group indicates the contribution of terrigenous sediment carried by coastal currents. The second group presents the same deposition dynamic with high accumulation of fine particles and organic carbon, indicating the domain of high productivity upwelling currents and oceanic vortices.

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Ultrasonic characterization of marine sediments: a preliminary study

Cited by 17 publications

References 11 publications

Erosion and Accretion on a Mudflat: The Importance of Very Shallow‐Water Effects

Erosion and Accretion on a Mudflat: The Importance of Very Shallow‐Water Effects

Optimization of hydrostatic pressure at varied sonication conditions – power density, intensity, very low frequency – for isothermal ultrasonic sludge treatment

Physical and geochemical properties of centennial marine sediments of the continental shelf of southeast Brazil

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