Particle Aggregate Breakup by Fluid Shear

Hunt, James R.

doi:10.1007/978-1-4612-4936-8_5

Cited by 30 publications

(9 citation statements)

References 49 publications

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“…Theory suggests that aggregate size varies with an inverse power of the turbulent-kinetic-energy dissipation rate (e.g. Hunt, 1986). Limited experimentation with natural aggregates, however, showed that dependence of size on turbulent-kinetic-energy dissipation rate is either not significant or weaker than predicted (Alldredge et al, 1990).…”

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

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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.

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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

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“…The coefficient Bk should generally be a function of the shear, diameter, and effective density of the floc as well as dependent on the particular sediment (Parker et al, 1972 ;Matsuo & Unno, 1981 ;Parker, 1982 ;Clark, 1982 ;Hunt, 1984). However, the dependence of Bk on these parameters has not been determined, and this quantity is still not well understood .…”

Section: Previous Work Flocculationmentioning

confidence: 99%

Flocculation and its effect on the vertical transport of fine-grained sediments

Lick

Ziegler

1992

Hydrobiologia

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Recent experimental and theoretical work on flocculation and settling speeds of flocs is reviewed. On the basis of this work, an accurate and computationally efficient model of the aggregation and disaggregation of fine-grained sediments is proposed . This model is then used to predict flocculation times and steady-state floc sizes for a wide range of environmental conditions. The predicted flocculation times are smaller, sometimes by as much as two orders of magnitude, than those predicted by mono-disperse theory. The model is also used to show that the disaggregation of flocs due to increased shear near the sediment-water interface may be a possible mechanism for the increased concentrations often observed near this interface .

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“…The rates and the dominant mechanisms of floc breakage are not well understood, nor even agreed upon (Hunt, 1986;Dyer, 1989;Alldredge et al, 1990;Milligan and Hill, 1998;. Models for floc breakage are complex, contain many adjustable parameters, and have not always been tested systematically against observations (e.g., Pandya and Spielman, 1982;Lu and Spielman, 1985;Ray and Hogg, 1987;Tsao and Hsu, 1989;Hsu and Tsao, 1992;Jackson, 1995;Hill, 1996;Spicer and Pratsinis, 1996;Kramer and Clark, 1999; McAnally and Mehta, 2000; Burd and Jackson, 2002;Ducoste, 2002;Lasheras et al, 2002;Nopens et al, 2002;Odriozola et al, 2002;Kostoglou, 2003).…”

Section: Introductionmentioning

confidence: 97%

“…Floc breakage is the disruption of flocs by stresses created by relative floc-fluid motion generated by turbulent fluctuations or by particle settling (e.g., Pandya and Spielman, 1982;Adler and Mills, 1979;Hunt, 1986). The rates and the dominant mechanisms of floc breakage are not well understood, nor even agreed upon (Hunt, 1986;Dyer, 1989;Alldredge et al, 1990;Milligan and Hill, 1998;.…”

Section: Introductionmentioning

confidence: 98%

Kinematic assessment of floc formation using a Monte Carlo model

Khelifa

Hill

2006

Journal of Hydraulic Research

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A simple stochastic model is proposed to simulate floc formation due to simultaneous aggregation and breakage processes. The model is based on the constant-number Monte Carlo method where the number of flocs is kept constant during simulations. To produce equilibrium floc-size distributions, it uses established models of flocculation and new simple formulations of breakage probability and of the probability of producing fragments of a given size from broken flocs. The concept of fractal geometry is used to describe the geometry of flocs. The maximum size of flocs allowed, the median size of component particles, and their density are the main inputs needed to simulate floc formation. Simulated steady-state floc-size distributions were compared with field data observed at different locations, and good agreement was obtained. Dimensional analysis applied to measured and simulated data revealed that floc-size distributions are self-similar and can be described by the same function, regardless of the conditions of their formation. RÉSUMÉOn propose un modèle stochastique simple pour simuler une formation de floculation due à des processus simultanés d'agrégation et de rupture. Le modèle est basé sur la méthode de Monte Carlo à nombre constant où le nombre de flocons est maintenu constant pendant les simulations. Pour obtenir des distributions de taille de flocons à l'équilibre, on utilise des modèles établis de floculation et de nouvelles formulations simples pour la probabilité de rupture et la probabilité de produire des fragments d'une taille donnée à partir flocons brisés. Un concept de géométrie fractale est employé pour décrire la géométrie des flocons. La taille maximum admise pour les flocons, la taille médiane et la densité des particules qui les composent sont les principales données requises pour simuler leur formation. Les distributions simulées de taille de flocons à l'état stationnaire ont été comparées à des données en nature observées à différents endroits, et on a obtenu une bonne concordance. L'analyse dimensionnelle appliquée aux données mesurées et les simulées a montré que les distributions de taille de flocons sont auto-semblables et peuvent être décrites par la même fonction, indépendamment des conditions de leur formation.

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Particle Aggregate Breakup by Fluid Shear

Cited by 30 publications

References 49 publications

Sediment Delivery to the Seabed on Continental Margins

Sediment Delivery to the Seabed on Continental Margins

Flocculation and its effect on the vertical transport of fine-grained sediments

Kinematic assessment of floc formation using a Monte Carlo model

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