Formulas for Sediment Porosity and Settling Velocity

Wu, Weiming; Wang, Sam S. Y.

doi:10.1061/(asce)0733-9429(2006)132:8(858)

Cited by 187 publications

(100 citation statements)

References 14 publications

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“…Therefore, the potential error when using Stokes' law to calculate the settling velocities of fractions of all sizes is considered acceptable. For soils dominated by larger mineral grains, different relationships should be used (Ferguson and Church, 2004;Wu and Wang, 2006). In addition, fine suspended fractions are considered as one group exported out of the terres- Starr et al (2000).…”

Section: Sediment Collection and Fractionation By A Settling Tube Appmentioning

confidence: 99%

Aggregates reduce transport distance of soil organic carbon: are our balances correct?

Kuhn

2014

Biogeosciences

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Abstract. The effect of soil erosion on global carbon cycling, especially as a source or sink for greenhouse gases, has been the subject of intense debate. The controversy arises mostly from the lack of information on the fate of eroded soil organic carbon (SOC) whilst in-transit from the site of erosion to the site of longer-term deposition. Solving this controversy requires an improved understanding of the transport distance of eroded SOC, which is principally related to the settling velocity of sediment fractions that carry the eroded SOC. Although settling velocity has already been included in some erosion models, it is often based on mineral particle size distribution. For aggregated soils, settling velocities are affected by their actual aggregate size rather than by mineral particle size distribution. Aggregate stability is, in turn, strongly influenced by SOC. In order to identify the effect of aggregation of source soil on the transport distance of eroded SOC, and its susceptibility to mineralization after transport and temporary deposition, a rainfall simulation was carried out on a silty loam. Both the eroded sediments and undisturbed soils were fractionated into six different size classes using a settling tube apparatus according to their settling velocities: > 250, 125 to 250, 63 to 125, 32 to 63, 20 to 32 and < 20 µm. Weight, SOC content and instantaneous respiration rates were measured for each of the six class fractions. Our results indicate that (1) 41 % of the eroded SOC was transported with coarse aggregates that would be likely re-deposited down eroding hillslopes, rather than with fine particles likely transferred to water courses; (2) erosion was prone to accelerate the mineralization of eroded SOC, and thus might contribute more CO 2 to the atmosphere than current estimates which often ignore potential effects of aggregation; (3) preferential deposition of SOC-rich coarse aggregates potentially causes an increase of SOC remaining in the colluvial system and a reduction of SOC flux to the alluvial or aquatic system. These findings identify a potential error of overestimating net erosion-induced carbon sink effects, and thus add an additional factor to consider when improving our current understanding of SOC erosion and deposition on hillslopes.

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Section: Sediment Collection and Fractionation By A Settling Tube Appmentioning

confidence: 99%

Aggregates reduce transport distance of soil organic carbon: are our balances correct?

Kuhn

2014

Biogeosciences

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“…Another approach is to use the following to estimate the settling velocity of a non-spherical particle (Wu and Wang 2006). The equivalent sphere is defined by Wu and Wang (2006) as a sphere having a settling velocity the same as the solid.…”

Section: 5mentioning

confidence: 99%

“…The equivalent sphere is defined by Wu and Wang (2006) as a sphere having a settling velocity the same as the solid. The diameter of the equivalent sphere, d E , is calculated by solving the following equation with the above calculated V S and known ρ L , ρ S and ν: …”

Section: 5mentioning

confidence: 99%

Hanford Waste Physical and Rheological Properties: Data and Gaps

Wells¹,

Kurath²,

Mahoney³

et al. 2011

103

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Executive SummaryThe Hanford Site in Washington State manages 177 underground storage tanks containing approximately 250,000 m 3 of waste generated during past defense reprocessing and waste management operations. These tanks contain a mixture of sludge, saltcake and supernatant liquids. The insoluble sludge fraction of the waste consists of metal oxides and hydroxides and contains the bulk of many radionuclides such as the transuranic components and 90 Sr. The saltcake, generated by extensive evaporation of aqueous solutions, consists primarily of dried sodium salts. The supernates consist of concentrated (5-15 M) aqueous solutions of sodium and potassium salts. The 177 storage tanks include 149 single-shell tanks (SSTs) and 28 double-shell tanks (DSTs).Ultimately the wastes need to be retrieved from the tanks for treatment and disposal. The SSTs contain minimal amounts of liquid wastes, and the Tank Operations Contractor is continuing a program of moving solid wastes from SSTs to interim storage in the DSTs. The Hanford DST system provides the staging location for waste feed delivery to the Department of Energy (DOE) Office of River Protection's (ORP) Hanford Tank Waste Treatment and Immobilization Plant (WTP). The WTP is being designed and constructed to pretreat and then vitrify a large portion of the wastes in Hanford's 177 underground waste storage tanks.The retrieval, transport, treatment and disposal operations involve the handling of a wide range of slurries. Solids in the slurry have a wide range of particle size, density and chemical characteristics. Depending on the solids concentration the slurries may exhibit a Newtonian or a non-Newtonian rheology.The extent of knowledge of the physical and rheological properties is a key component to the success of the design and implementation of the waste processing facilities. These properties are used in engineering calculations in facility designs. Knowledge of the waste properties is also necessary for the development and fabrication of simulants that are used in testing at various scales. The expense and hazards associated with obtaining and using actual wastes dictates that simulants be used at many stages in the testing and scale-up of process equipment. The results presented in this report should be useful for estimating process and equipment performance and provide a technical basis for development of simulants for testing.The purpose of this document is to provide an updated summary of the Hanford waste characterization data pertinent to safe storage, retrieval, transport and processing operations for both the tank farms and the WTP and thereby identify gaps in understanding and data. Important waste parameters for these operations are identified by examining examples of relevant mathematical models of selected phenomena including: The data sets in (UDS composition and particle density, UDS primary particle size and shape, UDS particle size distributions [PSDs], and estimated particle size and density distributions [PSDDs]) and Poloski et al. (2007) ...

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“…(4), it is necessary to establish a relationship between the porous gravel size D 50 and the porosity as well as the permeability. Wu and Wang (2006) developed an empirical equation given as:…”

Section: Open Channel Flow Over a Cylindermentioning

confidence: 99%

Macroscopic particle method for channel flow over porous bed

Jin

2017

Engineering Applications of Computational Fluid Mechanics

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This paper presents a new macroscopic mesh-free particle method in which Darcy's and Forchheimer's terms are introduced into the governing equation to ensure the capacity of the particle method in simulating laminar and turbulent porous medium flows. A developed interfacial condition and inflow boundary condition are implemented in the macroscopic particle method to improve the stability of the Particle-based model. The comparisons of channel flow over and within porous bed among the present method, previous mesh-based method, and experimental data show that the macroscopic particle method is capable of simulating flows in both the clear flow region and porous flow region. Finally, two cases of flow over a rigid box and a cylinder lying on porous bed are simulated, and the numerical results are in good agreement with the measured data. The analysis and comparisons indicate that the newly developed particle-based method is reliable and has been successfully extended to macroscopic porous medium simulation. ARTICLE HISTORY

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Formulas for Sediment Porosity and Settling Velocity

Cited by 187 publications

References 14 publications

Aggregates reduce transport distance of soil organic carbon: are our balances correct?

Aggregates reduce transport distance of soil organic carbon: are our balances correct?

Hanford Waste Physical and Rheological Properties: Data and Gaps

Macroscopic particle method for channel flow over porous bed

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