Direct measurements of settling velocities in the owen tube: A comparison with gravimetric analysis

Dearnaley, M.P.

doi:10.1016/s1385-1101(96)90769-8

Cited by 30 publications

(13 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…From a series of experiments (Wan, 2013) performed in a traditional settling column (Gibbs, 1972;Dearnaley, 1996) with a diameter of 40 cm, a height of 2.5 m, and with eight multi-depth outlets (intervals are 20 cm) for SSC sampling (Fig. 1), the following drawbacks of traditional experimental procedures could be identified: (1) Intakes are mounted at the fixed depths; therefore, the vertical SSC profile is not continuous to obtain a FV value of high resolution, the SSC gradient between each 2 outlets is ignored.…”

Section: Apparatusmentioning

confidence: 99%

Experimental study on fall velocity of fine sediment in the Yangtze Estuary, China

Wan

Roelvink

et al. 2015

Ocean Engineering

View full text Add to dashboard Cite

Section: Apparatusmentioning

confidence: 99%

Experimental study on fall velocity of fine sediment in the Yangtze Estuary, China

Wan

Roelvink

et al. 2015

Ocean Engineering

View full text Add to dashboard Cite

“…The observed increase in clearance rate with sediment concentration in Owen tubes has been linked conceptually and through direct and indirect observations to aggregation within the tubes (Milligan, 1995;Dearnaley, 1996;Milligan & Hill, 1998). These workers proposed that removal of sediment from a settling tube proceeds in several steps.…”

Section: Sediment Loss From Discharge Plumesmentioning

confidence: 99%

Sediment Delivery to the Seabed on Continental Margins

Hill

Fox

Crockett

et al. 2007

Continental Margin Sedimentation

View full text Add to dashboard Cite

On river-influenced continental margins, terrigenous muds tend to accumulate in the middle of the continental shelf. The common occurrence of mid-shelf mud belts has been attributed to three basic across-margin transport mechanisms. Muds either diffuse to the mid-shelf under the influence of storms, or they are advected there by oceanographic currents, or they arrive at the mid-shelf in dense suspensions that flow across the margin under the influence of gravity. Until recently, observations generally favoured the hypothesis that ocean currents are responsible for advecting dilute suspensions of mud to the mid-shelf. Transport by dense gravity flows was widely rejected, based primarily on the arguments that the bathymetric gradients of continental shelves are too small to sustain gravity flows, and that sediment concentrations cannot grow large enough to cause suspensions to flow down gradient. Observations conducted on the Eel River continental shelf off northern California, however, demonstrate that cross-margin transport by dense suspensions can be an important mechanism for the emplacement of muds on the mid-shelf. Dense suspensions form near the seabed when sediment in the wave boundary layer cannot deposit because of stress exerted on the bottom by waves, and when sediment does not diffuse out of the wave boundary layer because of relatively weak current-induced turbulence. In the future, the importance of these flows on other margins needs to be assessed.

show abstract

“…The use of in situ video techniques (e.g. Fennessy et al 1994;van Leussen and Cornelisse 1996;Manning 2006), which do not compromise the floc structure and which are not vulnerable to error induced by secondary circulation in settling columns (Dearnaley 1996), has greatly enhanced the reliability of settling velocity measurements. Manning (2008) undertook a combination of field-based and laboratory experiments to show that the flocculation of cohesive sediments could be well described by a set of empirically derived algorithms which include the effects of turbulent shear stress and concentration.…”

Section: Introductionmentioning

confidence: 99%

The settling dynamics of flocculating mud and sand mixtures: part 2—numerical modelling

2011

View full text Add to dashboard Cite

Estuarine and coastal sediment transport is characterised by the transport of both sand-sized particles (of diameter greater than 63 μm) and muddy fine-grained sediments (silt, diameter less than 63 μm; clay, diameter less than 2 μm). These fractions are traditionally considered as non-cohesive and cohesive, respectively, because of the negligible physico-chemical attraction that occurs between sand grains. However, the flocculation of sediment particles is not only caused by physicochemical attraction. Cohesivity of sediment is also caused by biology, in particular the sticky extra-cellular polymeric substances secreted by diatoms, and the effect of biology in binding sediment particles can be much larger than that of physico-chemical attraction. As demonstrated by Manning (2008) and further expanded in part 1 of this paper (Manning et al., submitted), the greater binding effect of biology allows sand particles to flocculate with mud. In many estuaries, both the sand and fine sediment fractions are transported in significant quantities. Many of the more common sediment transport modelling suites now have the capability to combine mud and sand transport. However, in all of these modelling approaches, the modelling of mixed sediment transport has still essentially separated the modelling of sand and mud fractions assuming that these different fractions do not interact except at the bed. However, the use of in situ video techniques has greatly enhanced the accuracy and reliability of settling velocity measurements and has led to a re-appraisal of this widely held assumption. Measurements of settling velocity in mixed sands presented by Manning et al. (2009) have shown strong evidence for the flocculation of mixed sediments, whilst the greater understanding of the role of biology in flocculation has identified mechanisms by which this mud-sand flocculation can occur. In the first part of this paper (Manning et al., submitted), the development of an empirical flocculation model is described which represents the interaction between sand and mud particles in the flocculation process. Measurements of the settling velocity of varying mud-sand mixtures are described, and empirical algorithms governing the variation of settling velocity with turbulence, suspended sediment concentration and mud-sand content are derived. The second part of this paper continues the theme of examination of the effects of mud-sand interaction on flocculation. A 1DV mixed transport model is developed and used to reproduce the vertical transport of mixed sediment fractions. The 1DV model is used to reproduce the measured settling velocities in the laboratory experiments described in the part 1 paper and also to reproduce measurements of concentration of mixed sediments in the Outer Thames. In both modelling exercises, the model is run using the algorithms developed in part 1 and repeated using an assumption of no interaction between mud and sand in the flocculation process. The results of the modelling show a significant improvement in the abilit...

show abstract

Direct measurements of settling velocities in the owen tube: A comparison with gravimetric analysis

Cited by 30 publications

References 1 publication

Experimental study on fall velocity of fine sediment in the Yangtze Estuary, China

Experimental study on fall velocity of fine sediment in the Yangtze Estuary, China

Sediment Delivery to the Seabed on Continental Margins

The settling dynamics of flocculating mud and sand mixtures: part 2—numerical modelling

Contact Info

Product

Resources

About