Settling Velocity Research Papers - Academia.edu (original) (raw)

Excel spreadsheet Settling Velocity.xls (2.1) calculates the terminal settling velocity of single spherical particles and of single natural sediment particles, in liquids and gases. It also predicts the hindered settling velocity of... more

Excel spreadsheet Settling Velocity.xls (2.1) calculates the terminal settling velocity of single spherical particles and of single natural sediment particles, in liquids and gases. It also predicts the hindered settling velocity of concentrated suspensions, by using Richardson & Zaki’s Law.
Guo (2002), Song Zhiyao et al. (2008), and Cheng (2009) combined the 3 “classical” settling velocity equations on laminar flow (Stokes’ Law), intermediate flow, and turbulent flow (Newton’s Law) each to only one relatively simple “new” settling velocity equation, used in this spreadsheet.
Calculations by these new settling laws are compared and contrasted with the sometimes tedious
classical calculations, and validated by graphical and manual sedimentation calculations.
13 worked examples illustrate how to use this spreadsheet, and how do manual calculations.

Turbidite slope channels are analogous to fluvial channels in that they tend towards graded equilibrium profiles. The gap between the equilibrium profile and the actual sediment surface defines the accommodation, and it is the creation or... more

Turbidite slope channels are analogous to fluvial channels in that they tend towards graded equilibrium profiles. The gap between the equilibrium profile and the actual sediment surface defines the accommodation, and it is the creation or removal of accommodation that governs the architectural style of turbidite channels on the slope. The factors that determine the tangent to the profile at a given point are the flow density, the flow thickness and the maximum settling velocity (a proxy for grain-size) of suspended sediment. These factors combine in a simple hydraulic relationship that illustrates how changes in these parameters affect the equilibrium gradient. In concept, graded channels behave like many sinuous fluvial systems in that the channels migrate laterally with little or no aggradation. Decrease in flow density or thickness, or increase in grain-size steepens the gradient and creates accommodation, allowing channels to aggrade. In fact without changes in other factors such as base level, channel aggradation should only occur when flow properties change. Increase in flow density or thickness, or decrease in grain-size reduce the gradient and remove accommodation, leading to erosional channels. Both long and short term changes tend from erosional to aggradational, with a tendency towards smaller and perhaps muddier flows with time.

Two important festival events were selected to assess their impacts on atmospheric chemistry by understanding settling velocity and emission time of aerosols. Using high volume sampler, aerosols were collected in a sequential manner to... more

Two important festival events were selected to assess their impacts on atmospheric chemistry by understanding settling velocity and emission time of aerosols. Using high volume sampler, aerosols were collected in a sequential manner to understand settling velocity and emission time of aerosols on a particular day. Composition and total suspended particulate load of the aerosols collected during the festivals were used as markers for strengthening the assessment. Terminal settling velocity of the aerosols were calculated using morphological and elemental compositional data, obtained from scanning electron microcopy (SEM) and energy dispersive X-ray (EDX) study. Aerosol load, black carbon, aromatic carbon and terminal velocity calculations were correlated to obtain conclusion that aerosols collected on the festival day might have been emitted prior to the festival. Settling time of aerosols collected on 17th and 19th October’09 during Diwali were found to be 36.5 (1.5 days) and 12.8 h, respectively. Carbon concentration estimated using EDX was found to be almost double in the sample collected after 2 days of the festival event. This strengthens our inference of time calculation where carbon with high concentration of load must have settled approximately after two days of the event. Settling time of aerosols collected on Holi morning and afternoon was found to be 1.7 and 24.8 h, respectively. Further, because of the small distance of 5.4 km between the meteorological station and sampling site, observed TSP values were compared with theoretical load values, calculated by using visibility values taken from the meteorological data. And it was found that both experimental and calculated values are close to each other about 50% of the times, which proves the assumption that experimental and meteorological data are comparable.► Concept of setting velocity was used to assess impact of festival events on the atmosphere chemistry. ► SEM-EDX analysis was used to determine terminal setting velocity. ► Correlation between BC, AOC and aerosol load was used to determine the settling time of the aerosols. ► Role of morphology of aerosols in altering the atmospheric chemistry was also highlighted in the study.

Two formulas are proposed for explicitly evaluating drag coefficient and settling velocity of spherical particles, respectively, in the entire subcritical region. Comparisons with fourteen previously-developed formulas show that the... more

Two formulas are proposed for explicitly evaluating drag coefficient and settling velocity of spherical particles, respectively, in the entire subcritical region. Comparisons with fourteen previously-developed formulas show that the present study gives the best representation of a complete set of historical data reported in the literature for Reynolds numbers up to 2 × 105.Two formulas are proposed for explicitly evaluating drag coefficient and settling velocity of spherical particles, respectively, in the entire subcritical region. Comparisons with fourteen previously-developed formulas show that the present study gives the best representation of a complete set of historical data reported in the literature for Reynolds numbers up to 2 × 105

The operation of nitrifying biomass as biofilms or granules allows the treatment of higher ammonia loads compared to the conventional activated sludge systems, due to the large amounts of biomass accumulated inside the reactors. In the... more

The operation of nitrifying biomass as biofilms or granules allows the treatment of higher ammonia loads compared to the conventional activated sludge systems, due to the large amounts of biomass accumulated inside the reactors. In the present work, a sequencing batch reactor (SBR) containing nitrifying granules with an average diameter of 1.9–2.9 mm was operated for 880 d at room temperature (18–24 °C). The obtained granules presented high settling velocities around 100 m h−1 and low sludge volumetric indexes of 30 mL (g VSS)−1 which indicated their good settling properties. When nitrogen loading rate (NLR) of 0.4 g NH4+-N L−1 d−1 was fed, complete nitrification to nitrate was reached. The increase of the NLR to 0.8 g NH4+-N L−1 d−1 caused a stable accumulation of nitrite with only 20% of nitrate production even by keeping the dissolved oxygen (DO) concentration in the bulk liquid at 8 mg O2 L−1. Batch assays performed in a range from 2 to 30 mg O2 L−1 of DO showed that partial nitrification was reached by fixing the DO concentration in the range from 2.0 to 3.5 mg O2 L−1 in the bulk liquid. The total surface of the granules to bulk liquid ratio was low and ranged from 58 to 216 m2 m−3 being the oxygen mass transfer through the interface bulk liquid–granule surface the limiting step. This oxygen transfer limitation allowed reaching stable partial nitrification at room temperature. For more than one year, an effluent with a mean NO2−/NH4+ molar ratio close to 1.0, suitable to feed a subsequent Anammox reactor, was obtained. A maximal nitrite production of 1 g NO2−-N L−1 d−1 was reached without nitrite oxidation to nitrate. The bacteria populations in the granules belonged mainly to the genus Nitrosomonas and were placed in the external layer of the granules of 100 μm.

This paper describes two semi-empirical formulas for the hindered settling velocity at high concentration. The first formula is based on the Richardson and Zaki formula (1954) with the inclusion of the effect of the maximum volume... more

This paper describes two semi-empirical formulas for the hindered settling velocity at high concentration. The first formula is based on the Richardson and Zaki formula (1954) with the inclusion of the effect of the maximum volume concentration of matter cmax≈0.65. The second formula is based on the solid-fluid mixture theory. Both expressions produce the best results among the studied formulas in the case of non-cohesive particles. The formula based on the fluid-mixture theory tends, however, to be sensitive to the estimation of the viscosity of the mixture. In the case of cohesive particles, as larger uncertainties exist due to unknown parameters as the density and the size of the flocs, no conclusion could be found. The Winterwerp (1999) formula gave similar results to the two proposed formulas. The estimation of the gelling concentration is also an important challenge, and appeared to correspond to for a volume concentration of the flocs =max≈0.8.

Coiled tubing (CT) has been recently applied for frequent drilling operation. Pushing the limits for coiled tubing drilling to include extended reach drilling is opposed by hole cleaning issues. Hole cleaning problems are claimed to be... more

Coiled tubing (CT) has been recently applied for frequent drilling operation. Pushing the limits for coiled tubing drilling to include extended reach drilling is opposed by hole cleaning issues. Hole cleaning problems are claimed to be critical in coiled tubing drilling due to lack of drillpipe rotation. This paper is intended to show how significant is the effect of not rotating the inner pipe on hole cleaning during coiled tubing drilling. The drillpipe was constrained at its ends only allowing it to exhibit eccentricity at the mid-section. This allows to simulate the whirling motion of the drillpipe which is claimed to add to good hole cleaning. The effect of pipe rotation was studied and the data collected were graphically correlated in the form of weight percent of recovered particles versus hole inclination at different drillpipe rotational speeds and annular fluid velocities. Results showed that pipe rotation significantly improve hole cleaning; up to 68% improvement was recorded for intermediate velocities (1.86 ft/sec & 2.29 ft/sec). The effect of pipe rotation is less significant at lower annular velocities and lower inclinations (1.43 ft/sec and 60 degree from vertical respectively); however, it has a significant effect at intermediate annular velocities but this effect is diminished with further increase in velocity. The results emphasized that turbulent flow are critical for cuttings removal at horizontal/highly deviated wellbores.

Submarine channel levees aggrade through repeated overspill events from the channel axis. The shape of the levees may therefore reflect some characteristic(s) of the overspilling flow. It has been noted that basin floor levees typically... more

Submarine channel levees aggrade through repeated overspill events from the channel axis. The shape of the levees may therefore reflect some characteristic(s) of the overspilling flow. It has been noted that basin floor levees typically have a relatively low-relief and taper exponentially to their termination; in contrast slope channel levees may be much steeper close to the channel. A simple physical experiment was performed where a surge-like sediment-laden current flowed through a curved channel. Significant overspill occurred and generated a deposit flanking the channel on either side. The experiment was repeated 25 times to build up low-relief channel-levees. It was found that in proximal areas, levees were steep and characterised by power-law decays, a transitional zone of logarithmically thinning levee was found a little further down-channel, followed by exponential decays in medial to distal areas. The style of levee decay is a function of spatial variation in overbank sedimentation rates. Where flows rapidly lose momentum and deposit across the grain-size spectrum, i.e., in proximal areas, levees tend to be steep; farther down the channel, the steep levee slope gives way to a more gradually tapering deposit. In more distal parts of the channel, deposition is directly related to sediment settling velocity (rather than the suspended load exceeding flow transport capacity as is the case in proximal areas), the deposit reflects this with relatively simple exponential thickness decays. Additionally, small-scale sediment waves developed under lee wave conditions on the inner-bend overbank. The waves initially migrated slightly towards the channel, but as the style of overspill evolved due to intra-channel deposition, flows moved out of the lee wave window and sedimentation became out of phase with the wavelength of the features and the topography was healed.

Rheological modelling of drilling fluids in oil fields is usually described by Bingham plastic and Ostwald-deWaele models. These models gain popularity because their specific descriptive parameters are fairly easy to estimate. Standard... more

Rheological modelling of drilling fluids in oil fields is usually described by Bingham plastic and Ostwald-deWaele models. These models gain popularity because their specific descriptive parameters are fairly easy to estimate. Standard methods use Fann VG meter dial reading at 600 and 300 rpm to determine these rheological parameters. Unfortunately, these points correspond to higher shear rates which seldom prevail during particle settling. Recently, many researchers pointed out that the non-Newtonian behavior of drilling fluids can be described well by the three parameters Herschle-Bulkley model. Again, the determination of its parameters using the standard API method make use of dial readings at 6 & 3 rpm to determine yield stress and 600 and 300 rpm to determine the other two parameters. Furthermore, the use of non-linear regression techniques to determine these parameters though deemed more accurate, sometimes give meaningless negative yield stress values. This work aims to investigate different techniques and shear rates to derive rheological parameters and show their influence on the magnitude of effective viscosity and hence settling velocity. It is demonstrated that very small differences among the values of the model parameters determined by different techniques/dial readings can lead to substantial differences in predicted settling velocities. Results of this work shows that the use of Herschle-Bulkley rheological parameters was by far the most accurate for representing the example muds rheograms as well as predicting the settling velocities, particularly when using non-linear regression values.

Adequate cuttings removal from the bottom hole of an oil well to the surface during a rotary drilling is critical for cost-effective drilling. The major factors that describe cuttings transport particularly in vertical sections are fluid... more

Adequate cuttings removal from the bottom hole of an oil well to the surface during a rotary drilling is critical for cost-effective drilling. The major factors that describe cuttings transport particularly in vertical sections are fluid effective viscosity and velocity
which influence particle settling velocity. Rheological modelling of drilling fluids in oil fields is usually described by Bingham plastic and power law models. These models gain popularity because their specific descriptive parameters are fairly easy to estimate. Standard methods use Fann V-G Meter dial reading at
600 and 300 rpm to determine these rheological parameters. Unfortunately, these points correspond to
higher shear rates which seldom prevail during particle
settling. This work aims to investigate different shear
rates to derive power law rheological parameters and
show their influence on the magnitude of effective
viscosity and hence settling velocity. The results show
that data pair of R600/R3 was the best to predict the full
spectrum of the fluid rheogram. Using Chien (1994)
correlation, data pair of R200/R100 give the best results
for predicting observed settling velocity of a nonspherical
particle settling in a static fluid. Data pair of
R200/R100 out performs commonly used data pairs
(R600/R300, R100/R3 and R6/R3). Furthermore, Using
modified Moore correlation with effective viscosity as
suggested by Chien obtained excellent predictions with
error less than 1% particularly with R600/R100.

and is providing both visible and infrared imaging observations of the martian surface at two scales (18 m/p and 100 m/p respectively). IR observations are being conducted during both day and night. IR imagery records temperature... more

and is providing both visible and infrared imaging observations of the martian surface at two scales (18 m/p and 100 m/p respectively). IR observations are being conducted during both day and night. IR imagery records temperature variations, which are primarily due to differences in abundances of rocks, indurated materials , sand, and dust on the surface. THEMIS has imaged all of the major outflow channels and valley networks. Outflow Channels: The source regions for the outflow channels contain large blocks of collapsed chaotic terrain with very coarse (rocky) slopes and talus aprons while the tops of these blocks appear smooth and mantled with finer grained materials (dust) or alternatively the tops of these blocks may be capped by a different material (relatively finer grained than the lower coarser talus producing material). This suggests that the blocks are made of strongly consolidated material capable of eroding into rocky debris. Layering along with cliff and ledge forming m...

The separation performance of a Floatex Density Separator (FDS) for Indian coals has been studied. Experimental results reveal that both density as well as size have substantial influence on separation performance. It is seen that at a... more

The separation performance of a Floatex Density Separator (FDS) for Indian coals has been studied. Experimental results reveal that both density as well as size have substantial influence on separation performance. It is seen that at a lower bed pressure the unit acts more like a classifier rather than a concentrator. With increasing bed pressure, the classification effect is, however, reduced and the concentration effect becomes more dominant due to proper development of suspension density. The separation performance of the FDS is described with density as well as size partitions. It is found that the size or density alone is not able to describe the separation fully. The terminal settling velocity, which includes both the size and density of a particle, can be a useful descriptor of separation in FDS. Ut50 may be defined as the terminal settling velocity of those particles that have equal tendency to report to the overflow or to the underflow stream. As a result, a higher teeter water flow rate helps in carrying larger-lighter particles to the overflow (higher settling velocity) by increasing the cut off terminal settling velocity as it increases the net upward force.

We use tank experiments to measure settling rates of deep-sea volcaniclastic material recovered from the Arctic (85°E Gakkel Ridge) and Pacific (Juan de Fuca Ridge, Loihi seamount) Oceans. We find that clast size and shape exert a strong... more

We use tank experiments to measure settling rates of deep-sea volcaniclastic material recovered from the Arctic (85°E Gakkel Ridge) and Pacific (Juan de Fuca Ridge, Loihi seamount) Oceans. We find that clast size and shape exert a strong influence on settling velocity, with velocities of ~30cm/s for large (~8mm), blocky clasts, compared to velocities of ~2.5cm/s for small (<0.5mm), sheet-like