Sedimentation Phenomena Research Articles

Microplastic occurrence and hydrodynamic-sedimentary driving effects in the Bohai Strait region of China.

The ubiquity of microplastics in oceans has led to an increased interest in microplastics in society. The Bohai Strait is in a key position in the Yellow and Bohai Seas and plays a key role in the exchange of materials and environmental changes in these waters. In this study, seawater, surface sediments, and column sediments, were collected from the Bohai Strait region. Among all seawater samples, the abundance of microplastics in the Bohai Strait region ranged between 0.38 and 3.20 items/L, and that of microplastics in surface sediments was between 15.80 and 94.41 items/kg d.w.. The average microplastics abundance in columnar sediments was 72.62±29.86 items/kg d.w., which provided key information on the spatial distribution of microplastics and sedimentation phenomena in the Bohai Strait region. The abundance of microplastics was higher in regions where currents flowed more slowly, which suggests that ocean currents exert a crucial effect on microplastic distribution. In addition, the abundance of microplastics in sediments showed a close relation to the deposition rate, which implies that the deposition rate contribute to the deposition process of microplastics on the seafloor. The type of microplastics in seawater influences the kind of microplastics in sediments, which further emphasizes the importance of microplastics in seawater during microplastic transport and the deposition process. The results of this research contribute to the in-depth understanding of the behavior and propagation pathways of microplastics in oceans and provide a valuable reference for the reduction of microplastic pollution.

Physicochemical Factors Affecting the Rheology and Stability of Peach Puree Dispersions

The rheological properties and sedimentation phenomena in fruit purees are of particular importance for the food industry and product acceptance by consumers. The aim of this study was to correlate the phase separation with the underlying mechanisms. First, the influence of soluble solids content and temperature on the flow properties of peach puree was determined. Furthermore, considering the fruit puree matrix as a colloidal dispersion, the sedimentation rate, particle size and zeta potential were also determined. The peach puree samples exhibited pseudoplastic behavior, which was effectively described by the power law model. Both the flow consistency coefficient and apparent viscosity increased as the concentration rose. On the contrary, viscosity decreased as temperature increased. In addition, there was no significant effect of temperature on the flow behavior index. Low zeta potential values resulted in sedimentation as expressed by the phase separation index, and the highest sedimentation rate was observed for the sample with the lowest sucrose content.

On the Use of Styrene-Based Nanoparticles to Mitigate the Effect of Montmorillonite in Copper Sulfide Recovery by Flotation.

Clay minerals have different negative effects on the froth flotation process such as low adsorption of collectors on valuable minerals, increased pulp viscosity, and the reduction in recovery and grade concentrates of copper sulfides. This study aims to evaluate the use of polystyrene-based nanoparticles (NPs) for the froth flotation of chalcopyrite and their ability to mitigate the negative effect of montmorillonite on the recovery of this sulfide. The experimental stage consisted of preparing a type of polystyrene-based nanoparticle (St-CTAB-VI), which was analyzed by dynamic night scattering (DLS) to establish its hydrodynamic size. Then, the effect of NPs on chalcopyrite's angle's in the presence and absence of montmorillonite (15%) was evaluated and compared with the contact angle achieved using potassium amyl xanthate (PAX) and a mixture of PAX and NPs. In addition, zeta potential measurements were carried out to investigate the interactions between the chalcopyrite and the montmorillonite or the NPs under fixed concentrations and microflotation tests were performed employing different times to evaluate the chalcopyrite recovery in the presence of montmorillonite, using NPs and mixtures with PAX. Finally, turbidity analysis as a function of time was performed to evaluate the occurrence of sedimentation and flocculation phenomena in suspensions of 15% montmorillonite in the presence and absence of chalcopyrite, nanoparticles, and mixtures of NPs and PAX. The results indicated that the mixture of NPs and PAX contributed to increasing the contact angle of chalcopyrite in the presence of montmorillonite. This can be associated with the presence of molecular and nanometric collectors that generated a higher hydrophobicity on the chalcopyrite particles, contributing to reducing the presence of clay minerals on the mineral surface. In addition, the mixture of NPs and PAX promoted the generation of nanoparticles on the sulfide mineral surface, which helps to detach the slime and facilitate the bubble/mineral attachment step during flotation.

A Rapid Detection Method for Coal Ash Content in Tailings Suspension Based on Absorption Spectra and Deep Feature Extraction

Traditional visual detection methods that employ image data are often unstable due to environmental influences like lighting conditions. However, microfiber spectrometers are capable of capturing the specific wavelength characteristics of tail coal suspensions, effectively circumventing the instability caused by lighting variations. Utilizing spectral analysis techniques for detecting ash content in tail coal appears promising as a more stable method of indirect ash detection. In this context, this paper proposes a rapid detection method for the coal ash content in tailings suspensions based on absorption spectra and deep feature extraction. Initially, a preprocessing method, the inverse time weight function (ITWF), is presented, focusing on the intrinsic connection between the sedimentation phenomena of samples. This enables the model to learn and retain spectral time memory features, thereby enhancing its analytical capabilities. To better capture the spectral characteristics of tail coal suspensions, we designed the DSFN (DeepSpectraFusionNet) model. This model has an MSCR (multi-scale convolutional residual) module, addressing the conventional models’ oversight of the strong correlation between adjacent wavelengths in the spectrum. This facilitates the extraction of relative positional information. Additionally, to uncover potential temporal relationships in sedimentation, we propose a CLSM-CS (convolutional long-short memory with candidate states) module, designed to strengthen the capturing of local information and sequential memory. Ultimately, the method employs a fused convolutional deep classifier to integrate and reconstruct both temporal memory and positional features. This results in a model that effectively correlates the ash content of suspensions with their absorption spectral characteristics. Experimental results confirmed that the proposed model achieved an accuracy of 80.65%, an F1-score of 80.45%, a precision of 83.43%, and a recall of 80.65%. These results outperformed recent coal recognition models and classical temporal models, meeting the high standards required for industrial on-site ash detection tasks.

Improved desalination performance of flow-electrode capacitive deionisation by a novel drop-shape channel

ABSTRACT As an emerging desalination technology, flow-electrode capacitive deionisation (FCDI) has the advantages of theoretically infinite adsorption capacity and applicability to high-concentration brine. However, during the operation of FCDI, the flow electrode in the S-shape channel is prone to sedimentation and clogging the channel. This undesirable phenomenon brings low efficiency and security issues. Therefore, a drop-shape channel was designed for FCDI to improve the flow regime of the flow electrode. The flow simulation of the drop-shape channel was performed to select the appropriate geometry to avoid the formation of the vortex and low-velocity region. The simulation results showed that the streamlined design of the drop-shape channel has insignificant velocity gradients. It significantly reduces the low-velocity region and improves the phenomenon of particle sedimentation. The desalination performance with varieties of electrode flow rate, AC content, and voltage was used to investigate the advantage between S-shape and drop-shape channels. It was found that under the conditions of low flow rate, high AC content, and high voltage, the drop-shape channel FCDI system could still obtain better ASRR and CE.

Assessment of the physical stability of cold brew coffee in retorted beverages

In recent years, the coffee market has launched many ready-to-drink cold brew coffee beverages (CBC). When bottled, producers face issues with the stability as consumers perceive the sedimentation phenomenon as a quality defect. As the physical stability in CBC is an emerging topic, it is necessary to characterize the sediment and understand its origin to identify mitigation alternatives. In this regard, regular and decaffeinated CBC in glass bottles over a period of 60 days were analyzed by microscopy and particle size distribution. Nano, amorphous and semi-crystalline particles were identified. Nanoparticles increased in the ∼0.1 μm range in the sediment of the regular CBC. Caffeine (+10%) and chlorogenic acid (CQAs) levels (+50%) in the supernatant filtrate increased after 60 days, which by scanning electron microscopy (SEM) revealed the topology of the identified particles, with a clear presence of the crystalline needles of caffeine, protein and potassium. X-ray diffraction analysis revealed that some peaks (3 out of 10), were associated with caffeine and sucrose, suggesting a complexation from the CQA presence; and supporting that the sediment might be mostly potassium chlorogenate complex. As the phenomenon was prevalent in the regular CBC, the presence of caffeine in the formation is key.

The Influence of Graphite Filler on the Self-Lubricating Properties of Epoxy Composites.

In this work, epoxy composites filled with flake graphite of various size (less than 10 μm and less than 45 μm) were produced. The aim of the research was to develop a self-lubricating material with favorable tribological properties, i.e., reduced friction coefficient compared to unfilled epoxy resin and limited abrasive wear. The research material was produced using technical epoxy resins based on bisphenol A. The detailed process of composite production was described, and typical technological problems were considered. The addition of graphite led to an increase in dynamic viscosity, which positively limits the phenomenon of sedimentation, but an increase in the filler content also led to an increase in the porosity of the material. A series of tests have shown that the addition of graphite above 5% by weight allows for a reduction in the friction coefficient from 0.6 to 0.4 and significantly reduces the material's tendency to abrasive wear.

An energy estimate and a stabilized Lagrange–Galerkin scheme for a multiphase flow model

Multiphase flow models are commonly employed for understanding complex fluid flows, while few mathematical discussions exist. For a general multiphase flow model in Gidaspow (1994), an energy decay property is proved. A stabilized Lagrange–Galerkin scheme for the model and its stability property are presented. Here, a hyperbolic tangent transformation is employed to preserve the boundedness of the volume fraction. A novel artificial term is added to obtain the stability property. Two-dimensional numerical examples exhibit the experimental order of convergence and applicability in modelling sedimentation phenomena.

Numerical Simulation of Pipeline Scour and Sedimentation around Submerged Pipelines with an Open-Source Multiphase-CFD Model

This paper presents a comprehensive study on pipeline scour and sedimentation phenomena using an open-source multiphase Computational Fluid Dynamics (CFD) model. The research focuses on understanding the complex interactions between fluid flow, sediment transport, and scour formation around submerged pipelines. The proposed analysis aims to enhance the understanding of scour development and sedimentation deposition, which is crucial for the design, operation, and maintenance of various engineering structures, including offshore pipelines and underwater infrastructure. The results show that the model exhibits the ability to compute sediment transport without depending on traditional assumptions related to bed-load and suspended-load layers. The simulation results affirm the model's proficiency in replicating the underlying mechanisms accountable for the onset of these processes, notably seepage flow and piping. Furthermore, this model can successfully depict the vortex phenomenon, which promotes the accumulation of sediment around the pipe. This phenomenon arises from the contrast in pressure between the centre of the vortex and the pressure exerted on the sediment beneath it.

An experimental and numerical study investigating sediment transport position in the bed of sewer pipes in Karbala

Abstract The complex phenomenon of sedimentation in urban areas is well studied using numerical models. Because they may be used to mimic sediment flow, obstructions, and drainage system optimization, the simulations are useful in urban planning and design. By merging ANSYS Fluent with Rocky, researchers were able to track the motion of sediment particles of various sizes and speeds. The sizes of the sediment particles were measured using a sieve after being collected from the streets of Karbala. The particle sizes established by the sieve analysis were used in both the computational and experimental procedures. Varied particle sizes and velocities, including 0.1, 0.2, 0.3, 0.35, 0.4, and 0.49 m/s, as well as varied particle sizes, including 0.4, 0.6, 0.8, 0.1, and 1.2 mm, were investigated. Numerical analysis showed that 1.2 mm-sized particles sedimented between 10 and 148 cm from the input pipe’s X coordinate at a rate of 0.49 m/s. A maximum sedimentation distance of 380 cm was also observed for particles with a diameter of 1 mm. Sediment did not include 0.4 mm-sized objects flowing at the same speed. The findings demonstrated that particle size and velocity significantly impacted the quantity of drag and lift forces acting on the particles. As the particle size increased, the drag force increased, which led to more sedimentation. The particle positions along the X coordinate (pipe bed) showed a declining trend. Overall, this work offers crucial insights for understanding sediment transport in urban drainage systems by illuminating the connection between velocity, particle size, and sedimentation behaviour.

Analyzing coastal erosion and sedimentation using Sentinel-1 SAR change detection: An application on the Volta Delta, Ghana

Ghana's coastline has been facing erosion and sedimentation phenomena for several decades, resulting in a serious threat to life and property considering that major urban settlements are located on the coast. In this region, there has been a lack of emphasis on comprehensive, large-scale investigations into coastal changes: prior research has predominantly centered on site-specific assessments. These studies have revealed alarming erosion rates, with reports indicating that nearly ten meters are lost annually. The use of high-resolution remotely sensed data can be a consistent support in regions where physical or economic obstacles interfere with collecting in situ information. In particular, the use of continuous all-weather SAR data may facilitate the evaluation of erosion and sedimentation phenomena in coastal areas. In this paper, we apply SAR data over a time period between 2017 and 2021. Sentinel-1 data are pre-processed using the Google Earth Engine platform, and a dedicated algorithm is then applied to identify and quantify erosion and sedimentation processes. Optical images are used as a reference for detecting the location of two areas where consistent sedimentation and erosion phenomena occurred in the considered four years. The results demonstrate that SAR backscattering variations over time offer a reliable method for monitoring coastal changes. This approach enables the identification of the type of phenomena occurring - sedimentation or erosion -, and allows for the quantification of their intensity and dimensions over time. The method can be worldwide applied once the appropriate thresholds are evaluated and help in predictive studies and environmental planning.

Analytical and numerical investigation of viscous fluid-filled spherical slip cavity in a spherical micropolar droplet

<abstract><p>This article presents an analytical and numerical investigation on the quasi-steady, slow flow generated by the movement of a micropolar fluid drop sphere of at a concentrical position within another immiscible viscous fluid inside a spherical slip cavity. Additionally, the effect of a cavity with slip friction along with the change in the micropolarity parameter on the movement of the fluid sphere is introduced. When Reynolds numbers are low, the droplet moves along a diameter that connects their centres. The governing and constitutive differential equations are reduced to a computationally convenient form using appropriate transformations. By using the resulting linear partial differential equations for the stream functions and using the method of separation variables, we can obtain their solutions. General solutions for velocity fields are found using spherical coordinate systems, which are based on the concentric point of the cavity; this allows to obtain solutions to the Navier-Stokes equations internal and external to the spherical droplet. The vorticity-microrotation boundary condition is used in regard to the micropolar droplet case in a viscous fluid. The normalised drag forces acted upon the micropolar drop are illustrated via graphs and tables for diverse values of the viscosity ratio and drop-to-wall radius ratio, with the change of the spin parameter that attaches the microrotation to vorticity. The correction wall factor is shown to increase with an increase in the drop-to-wall radius ratio, when moving from the gas bubble case to the solid sphere case, with an increase in the micropolarity parameter, and with an increase in the slip frictional resistance. This study is relevant due to its potential uses in a variety of biological, natural, and industrial processes, including the creation of raindrops, the investigation of blood flow, fluid-fluid extraction, the forecasting of weather conditions, the rheology of emulsions, and sedimentation phenomena.</p></abstract>

Assessing dispersion stability of alumina colloids via thermal characterization of the sediment layer

Colloidal suspensions incorporating particles are pivotal in diverse industries because of their distinct properties. However, challenges such as particle aggregation and sedimentation have impeded their widespread application. Existing techniques for assessing dispersion stability have limitations with respect to the particle type, concentration, and suspension properties. This study focuses on an innovative approach for assessing the dispersion stability and presents a streamlined method for analyzing the particle size and distribution. A theoretical model considering gravity, buoyancy, and viscous forces acting on the particles was developed to calculate the time-varying thickness of the sediment layer at the bottom of the sample colloid. The 3ω method is employed to measure thermal resistance changes at the sample droplet's bottom due to sedimentation. An empirical comparison utilizing Al2O3 particles in deionized water validates the efficacy of the method in understanding sedimentation mechanisms. In addition, a stability constant was proposed to quantitatively compare sedimentation phenomena, factoring in mixing methods, time, particle concentration, and shelf time. This study enhanced the quantification of the dispersion stability of colloids by enabling swift and precise assessment of particle concentration, size, and distribution inside a sample droplet.

Research on wear characteristics of U-shaped elbows based on CFD-DEM coupling

The C++ programming language is employed to improve the Computational Fluid Dynamics (CFD)- Discrete Element Method (DEM) coupling interface in this paper, the accuracy of solid-liquid two-phase flow numerical model are validated through experiments. Subsequently, the wear characteristics of the U-shaped elbows under different elbows spacing, bending diameter ratio, particle volume concentration, and particle size are investigated. The research results indicate that as the spacing between bends is increased, the phenomenon of particle sedimentation is intensified, and the maximum collision angle in elbow 2 is increased. The location of the maximum collision angle is closer to the outlet of elbow 2. However, both the collision frequency and wear rate are reduced due to the decrease in the number of particles. Smoother particle flow and a reduction in the collision angle and wear rate of particles on both bends are achieved by increasing the bend ratio. During the variation of the particle volume fraction from 0.5% to 7%, the increase in collision frequency and wear rate of both bends is slowed down. A greater decrease is observed in elbow 2, but the “shielding effect” is not observed. Furthermore, at low volume fractions, kinetic energy is lost by particles as they flow through elbow 1, resulting in a lower average wear rate in elbow 2 compared to elbow 1. Conversely, at high volume fractions, the opposite effect occurs. Finally, when keeping the particle volume fraction constant, an increase in the particle size leads to a smaller wear area in both bends. The wear rate in elbow 1 increases at a slower rate, while the wear rate in elbow 2 exhibits an initial increase followed by a decrease trend.

Thermo-optical performance of building glass under salt sedimentation

The phenomenon of salt sedimentation on the building glass surface occurs in coastal salt-fog climates, leading to the changes in surface heat transfer characteristics and optical properties, which affects the indoor environment and gradually reduces building energy performance. Regrettably, there remains a paucity of research concerning the impact of salt sedimentation on the thermal and optical performances of building glass. This study investigated the salt sedimentation features of building glass using an indoor accelerated test, and explored the relationships between surface heat transfer coefficients, optical properties and salt sedimentation. As the spray duration grew, the sedimented salt stains appeared more dispersed and less dense, but their dimensions increased, exhibiting an exponential growth tendency. The salt sedimentation per unit area grew logarithmically with the spray duration, with the magnitudes being 14.4 to 40.0 mg/m2 and 15.6 to 44.3 mg/m2 under 5% and 10% brine concentration conditions, respectively. The convection heat transfer coefficient (CHTC) and radiative heat transfer coefficient (RHTC) showed a linear monotonic increase with the salt sedimentation, in contrast to the control condition, with the maximum growth rates reaching 178.7% and 97.2%, respectively. The extended CHTC model could be used to calculate the CHTC regarding the impact of salt sedimentation and wind speed. The entire solar spectral transmittance and reflectance was affected by salt sedimentation, and the visible light transmittance, reflectance, hemispherical emissivity, and shading coefficient of low-E and clear glasses all decreased linearly with the increase of salt sedimentation.

Effects of a spherical slip cavity filled with micropolar fluid on a spherical viscous droplet

An analytical study for the quasisteady flow caused by a spherical viscous fluid droplet translating at a concentric position in a second immiscible micropolar fluid within a spherical cavity with a slip surface is presented. Attention is focused on the case when one of the two fluid phases has a microstructure nature (micropolar fluid). The droplet translates along a diameter connecting their centres under the conditions of low Reynolds numbers. To solve the Stokes equations for the velocity fields inside and outside the droplet, general solutions are obtained in terms of spherical coordinates based on the concentric position. For the case of the viscous droplet within a micropolar fluid, a boundary condition related to vorticity with microrotation is used. The wall correction factors acted on the viscous droplet for the different cases are represented through graphs for various values of relative viscosity, radii ratio of droplet and cavity, and the parameter that connects the vorticity with microrotation. The wall-corrected drag force is found to be a monotonically increasing function of the ratio of drop-to-cavity radii. The present work is important because of its applications in various natural, industrial, and biological processes, such as raindrop formation, the study of blood flow, liquid–liquid extraction, the prediction of atmospheric conditions, sedimentation phenomena, and the rheology of emulsions.

Evaluation of the local kinetics of a colloidal system through diffusion–sedimentation phenomena: A numerical approach

Evaluation of the local kinetics of a colloidal system through diffusion–sedimentation phenomena: A numerical approach

The Assessment of Sedimentation Problems in Kenyir Hydropower Reservoir, Malaysia

Lakes may take a while to respond to management interventions because of the management implications of incremental development and degradation issues. This includes the requirement for the ongoing participation of key lake basin management institutions and their operations. This study’s objective is to assess the impacts of land use activities along the Kenyir Lake Basin based on the sedimentation problem level. There are a few hydrological methods that are necessary indicators to measure the level of sediment production, such as Total Suspended Solid (TSS), area of sub-catchment, river discharge measurement, and annual sediment load production. The results showed that the sub-catchment of Besar River released the lowest annual average estimation at 3833.70 kg/km2/year, and the sub-catchment of Kenyir River produced the highest annual average estimation at 128,070.86 kg/km2/year for annual sediment load flow produced from tributary rivers into Kenyir Lake. Kenyir Lake Basin’s downstream and midstream regions had higher sediment load values than its upstream regions. This study highlighted the significance of the effects of anthropogenic factors, hydrological, geomorphological, growth, and developmental factors, and climate changes as the key variables attributing to the sedimentation phenomenon along the Kenyir Lake Basin. The construction of a long-term lake or reservoir catchment development and management plan, combined with the formation of a vision and comprehensive strategic plan, are vital components of sound management practice. The efficient implementation of the suggested watershed management programmes depends on the active involvement of all significant catchment stakeholders.

Empirical modeling of ex-vessel debris bed formation in a pre-flooded reactor cavity

To secure the containment integrity of a nuclear power plant (NPP) in severe accident situation of ex-vessel corium release into the reactor cavity, a pre-flooding strategy of a reactor cavity has been adopted in various NPPs, including Korean PWRs. Molten corium released into the pre-flooded water pool is fragmentized and forms a particulate debris bed at the bottom of the cavity. To prevent the containment failure, it is important to properly remove the heat from the debris bed, which can be accomplished by water ingression into the bed. The water ingression characteristics are highly dependent on the debris bed shape. In this study, several main parameters affecting the debris bed shape were determined with respect to phenomena of free-fall & sedimentation, particle dispersion by steam spike and convection flow, and self-leveling. Then empirical model was developed and validated using the results of DEFCON (Debris bed Formation and COolability experimeNt) experiments. The model’s error was within ±10% when only free-fall & sedimentation were present. When steam-spike or convection was added to free-fall & sedimentation condition, the error increased to within ±20%. When all three were simultaneously present (free-fall & sedimentation, steam-spike, and convection), the model predicted most of the experimental results within ±20% error, except for several cases where convection had a significant impact. The effect of self-leveling itself was within ±10%. Considering all phenomena related to particulate debris bed formation, most cases had an error of ±20%. In addition, the debris bed shape formed by poly-disperse particles was predicted appropriately by the mode using the mass mean diameter of the particle size distribution, with an error range of ±20%. Consequently, it is expected that the proposed model of the debris bed shape can be utilized in an integrated severe accident analysis code for the evaluation on the ex-vessel debris bed coolability in the pre-flooded reactor cavity.

On the detection of nanoparticle cloud migration by a resonant photonic surface signal towards sedimentation velocity measurements

Migration and sedimentation of solid particles in a liquid are physical phenomena involving accumulation of soft matter or decantation of fragmented matter. A thorough understanding together with relevant measurements are prerequisites regarding many fields, including medicine, galenic pharmacology, food processing, and the cosmetics industry. In this paper, we investigate the feasibility of monitoring and detecting the migration of a nanoparticle cloud with a resonant light probe. For this purpose, hybrid silicon/silica/UV210 organic integrated photonic racetrack resonators were patterned by thin film processes to be used as sensors measuring the outcome of the impact of a cloud of nanoparticles, the dynamic migration plus sedimentation phenomenon of the nanoparticle cloud in water. A broadband superluminescent diode has been used for the excitation. Then, the spectral characteristics of the resonant guided modes have been analyzed, considering the observed changes while tracking the free spectral range of the transduced comb spectra as a function of time. The way to operate can be summarized as follows: Solutions based on spherical silica nanoparticles of fixed size are prepared and subjected to rheological measurements to obtain their respective viscosities. Next, a millimeter tank filled with water is conveniently placed on the active surface of the sensing chip, prior to the addition of one of the previously mentioned solutions. The series of spectra are acquired during the whole migration sequence and the transduced optical signal is then directly processed and treated by a specific code operated in real time by way of Lagrange interpolation polynomials. Collected data are then compared to a simple theoretical model describing the sedimentation of a spherical particle in water (Stokes' law). Eventually, the implementation of the device in a characterization platform and the development of a specific protocol allows a global treatment, whose description is followed by discussions on measurements and data. Consequently, after the impact of the drop containing the nanoparticles, the monitoring of a first phase regarding their fast cloud migration into the global study volume (with flow of matter plus vortex) eventually followed by their slow sedimentation, can be detected using such a resonant light probe. The overall duration of the first phase associated with sedimentation velocities is in the order of a few tens of µm/min for particles with submicron diameters (several hundreds of nanometers); a first attempt of comparison of this first phase with the results of the classic Stokes model would give a convergence of the values reaching between 9 and 19% for the sedimentation rates.