Sedimentation Velocity Of Particles Research Articles

Processing reflectivity and Doppler velocity from EarthCARE's cloud-profiling radar: the C-FMR, C-CD and C-APC products

Abstract. The Earth Clouds, Aerosols and Radiation (EarthCARE) satellite mission is a joint effort by the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA). The EarthCARE mission features the first spaceborne 94 GHz cloud-profiling radar (CPR) with Doppler capability. The raw CPR observations and auxiliary information are used as input to three Level-2 (L2) algorithms: (1) C-APC: Antenna Pointing Characterization; (2) C-FMR: CPR feature mask and reflectivity; (3) C-CD: Corrected CPR Doppler Measurements. These algorithms apply quality control and corrections to the CPR primary measurements and derive important geophysical variables, such as hydrometeor locations, and best estimates of particle sedimentation fall velocities. The C-APC algorithm uses natural targets to introduce any corrections needed to the CPR raw Doppler velocities due to the CPR antenna pointing. The C-FMR product provides the feature mask based on only-reflectivity CPR measurements and quality-controlled radar-reflectivity profiles corrected for gaseous attenuation at 94 GHz. In addition, C-FMR provides best estimates of the path-integrated attenuation (PIA) and flags identifying the presence of multiple scattering in the CPR observations. Finally, the C-CD product provides the quality-controlled, bias-corrected mean Doppler velocity estimates (Doppler measurements corrected for antenna mispointing, non-uniform beam filling and velocity folding). In addition, the best estimate of the particle sedimentation velocity is estimated using a novel technique.

Cyclic Thermal Shock Response of Zirconia/304 Stainless Steel Functionally Graded Materials Fabricated by Centrifugal Slurry Methods

Functionally graded materials (FGMs) are multi-phase composites with gradual spatial variations of constituents. The compositional transitions in the FGMs are classified into two manners such as continuous gradient manners and stepwise manners. In this study, zirconia (ZrO2)/ 304 stainless steel (SUS304) FGMs with continuous gradient manners were fabricated by a combination of centrifugal slurry methods and spark plasma sintering (SPS). A variety of continuous gradient patterns were achieved by controlling the amount of dispersant such as ammonium polycarboxylic acid (PCA) in the slurry. With an increase in the amount of PCA, the gradient patterns in the FGMs changed from ceramic (ZrO2)-rich to metal (SUS304)-rich ones. According to Stokes sedimentation velocity simulations, the sedimentation velocity of SUS304 particles is higher than that of ZrO2 particles. With an increasing amount of PCA, the sedimentation velocity of the particles decreases. Cyclic thermal shock test results demonstrated that FGMs with metal (SUS304)-rich continuous gradient patterns showed the highest resistance among the samples of FGMs, 5-layered materials and ZrO2 single materials.

Методический подход к изучению седиментационной устойчивости тонкодисперсных отходов переработки минерального сырья по спутниковым данным загрязнения природных водоемов

The paper presents the results of the study of sedimentation stability of suspended finely-dispersed mineral particles based on satellite observations of their aggregation and sedimentation. The authors studied satellite data on self-purification of subarctic lakes polluted by apatite-nepheline, iron, and copper-nickel ore processing wastes. The multispectral images of lakes taken by Sentinel-2 spacecraft have allowed determining the average size of suspended finely-dispersed mineral processing wastes and the density of particle size distribution. To account for aggregation, the authors have designed a computer model of the dynamics of suspended particles and have set parameters of the forces of electrostatic and dispersion interactions of mineral particles from the Kola deposits. It is shown that the balance of repulsive electrostatic and dispersion attractive forces appears in the generation of aggregates of finely-dispersed mineral particles with characteristic fractal dimension, using Nepheline, Hematite, Quartz, and Pyrite as examples. The authors have developed an algorithm for matching the computer simulation results of the dynamics of suspended particles with the results of satellite images processing of lakes. The developed methodological approach makes it possible to determine the sedimentation stability of lakes’ pollution by finedispersed mineral processing wastes without surface observations. The research results allow calculating the sedimentation velocity of mineral particles and their aggregates of a given size. The good correspondence between the calculated parameters of particles aggregation and sedimentation and satellite observations data can be used to monitor the pollution of water bodies when adapting mineral processing technologies to modern production ecologization requirements, as well as to assess the waterenvironmental potential of the territory for rational management of natural resources.

Influence of inelastic collision on the dynamic behavior of particle sedimentation in high-viscosity fluids

To further understand the characteristics of particle–fluid flow, the particle sedimentation process in a high-viscosity fluid is conducted with both experimental and numerical methods. In this work, inelastic collisions between particles during the sedimentation process are observed. Different from the sedimentation in a low-viscosity fluid, the increase of particle sedimentation velocity can be found due to the inelastic collisions in a high-viscosity fluid. This phenomenon is more obvious with the increase of the particle volume fractions and the viscosity of the fluid. The necessary conditions for the inelastic collision phenomenon are determined based on the viscous dissipative dynamics of particle collisions. According to the experimental and numerical results, the interactions between particles in high-viscosity liquids are mainly the inelastic collisions which caused the particle aggregation. The correction coefficient of particle sedimentation velocity equation is obtained, and the applicability of the equation for the sedimentation in a high-viscosity fluid is improved.

The assessment of average cell number inside in-flight 3D printed droplets in microvalve-based bioprinting

3D cell bioprinting is an innovative and time-saving additive manufacturing technology; it precisely generates complex cell-laden constructs to overcome the limitations of 2D cell culture and conventional tissue engineering scaffold technology. Many efforts have been made to evaluate the bioprinter performance by considering printed cell number and the consistency of printed cell number. In this paper, a modified droplet imaging system is used to study the printing performance for a micro-valve-based 3D bioprinter using fluorescence MCF-7 cells. The effects of droplet dispensing physics (dosing energy Ed), ink properties (Z number—the inverse of the Ohnesorge number and particle sedimentation velocity), and input cell concentration are considered. The droplet imaging system demonstrates a strong capability and accuracy in analyzing bioprinting performance for printed cell density less than 300 cells/droplet. The average printed cell number is positively correlated with the increasing input cell concentration, dosing energy, and printing time. Printing ink, with Z number ranging from 4 to 7.41 and cell sedimentation velocity at 9.45×10−8 m/s, can provide the estimated printed cell number and consistent cell printing results within 2 min printing time. Printing inks with higher Z number or cell sedimentation velocity should be ejected under dosing energy below 2.1 La and printed right after filling the reservoir to achieve reliable and stable printing results.

Apparent Viscosity Measurement of Solid-liquid Coexisting Fluid by Falling Ball Method for Evaluation Iron Particle Sedimentation Velocity in Slag

Apparent Viscosity Measurement of Solid-liquid Coexisting Fluid by Falling Ball Method for Evaluation Iron Particle Sedimentation Velocity in Slag

The characterization of particle number and distribution inside in-flight 3D printed droplets using a high speed droplet imaging system

3D bioprinting is an innovative and time-saving method to precisely generate cell-laden 3D structures for clinical and research applications. Ejected cell number and cell distribution are two key technical parameters for evaluation of the bioprinter performance. In this paper, a modified droplet imaging system is used to study cell-size fluorescent particle number and distribution within droplets ejected from a microvalve-based 3D bioprinter. The effects of droplet dispensing physics (dosing energy Ed), ink properties (Z number—the inverse of the Ohnesorge number and particle sedimentation velocity), and input particle concentration are considered. The droplet imaging system demonstrates a strong capability in analyzing bioprinting performance for seeded concentrations less than 3×106 particles/ml. The printed particle number increases near-linearly under increasing dosing energy and Z number. It was found that for 7<Z<21 and seeded particle concentration no less than 3×106 particles/ml, particles within the visualized droplets approached a homogeneous distribution in the 2D images. It was also determined that the particle sedimentation velocity within the ink has a positive relationship to the ejected particle number over time—with the particle distribution approaching a homogeneous state over increasing sedimentation time.

MATHEMATICAL MODEL FOR MEASURING THE CONCENTRATION OF NANOPARTICLES IN A LIQUID DURING SEDIMENTATION

Expanding the application areas of polymer composite materials with dispersed filler requires the development of technologies providing the required mechanical characteristics. One of these methods is based on forming a thin polymer shell on the surfaces of particles. At the same time, it is impossible to take into account the mechanical characteristics of a thin polymer shell due to its ultra-small thickness. The mechanical properties of the polymer shell can be determined only by indirect methods, and prior information can improve the adequacy of the properties determination. The method, which allows reducing the requirements for composite sample preparation, is proposed. This method is based on the sedimentation approach. It is suggested to evaluate the sedimentation time (or velocity) by measuring the optical density of the solution, consisting of nanoparticles and polymer macromolecules. The nanoparticle and polymer macromolecules parameters are defined using sedimentation time. The mathematical model for simulation of the photo sedimentation velocity of particles in a solvent is developed. The model considers the sedimentation process under the influence of gravity, hydrostatic lift, and drag forces. The model takes into account also the influence of the Brownian motion of the solvent on the particle movements based on elastic collision as well as the effect of the inelastic collision of particles with each other. The particle concentration is estimated based on beam light scattering modeling. The results of the mathematical model investigation and the experimental results confirm the feasibility of the proposed method. The results and estimations allow both to determine the sedimentation time and to formulate the method requirements for measuring particles of various sizes and densities. The proposed approach can be used to create equipment for nanoparticle parameters (mass, density) measuring.

Ensemble average and nearest particle statistics in disperse multiphase flows

Abstract

Sedimentation of finite-size particles in quiescent wall-bounded shear-thinning and Newtonian fluids

We study the sedimentation of finite-size particles in quiescent wall-bounded Newtonian and shear-thinning fluids by interface resolved numerical simulations. The suspended phase consists of Non-Brownian rigid spherical particles with particle to fluid density ratio ρp/ρf=1.5 at three different solid volume fractions Φ=1%, 5% and 20%. Firstly, to focus on the effect of shear-thinning on the particle dynamics and interactions, the Archimedes number is increased for a single particle to have the same settling speed in the Newtonian fluid as in the shear-thinning fluid. Secondly, we consider fixed Archimedes and vary the shear-thinning properties of the fluid. Overall, we report a twofold effect of shear thinning. First and more important, the substantial increase of the particle sedimentation velocity in the shear-thinning case due to the increase of the shear rate around the particles, which reduces the local viscosity leading to a reduced particle drag. Secondly, the shear-thinning fluid reduces the level of particle interactions, causing a reduction of velocity fluctuations and resulting in particles sedimenting at approximately the same speed. Moreover, the mean settling velocities decrease with the particle concentration as a consequence of the hindering effect. Particles tend to sediment in the middle of the channel, preferentially positioning in the wake of neighbouring particles or aside them, resulting in lower levels of fluid velocity fluctuations in the gravity direction in the shear-thinning fluid.

Statistical characterization of sedimentation velocity of natural particles

Aeolian sediment transport has major repercussions for global climatic variations, air quality, human health, agricultural areas, air and ground transportation, civil structures and infrastructures. This led to the development of models to understand the involved physical process, and to predict the dynamics of aeolian sediment transport. The sedimentation velocity is one of the key model parameters characterizing sediment behavior. It allows the prediction of the mode of transport, the distribution of particles above the ground, and the sediment transport rate. Despite its importance, there is substantial discrepancy among the sedimentation velocity laws for natural particles, also due to the large dispersion of experimental data. This study proposes the statistical characterization of the experimental measurements of sedimentation velocity available from the literature. 1812 experimental measurements were recovered from 11 studies. Their variability was discussed, providing an aerodynamic reading. Nonlinear regression was carried out on the consolidated dataset in order to assess the average value. Two well-known laws initially conceived for spheres were refitted to natural particles providing high coefficients of determination equal to 0.90 and 0.93. Then, copula-based regression was performed in order to seize the variability of sedimentation velocity. Finally, the results from the two approaches were compared and critically discussed.

The study of magnetorheological fluids sedimentation behaviors based on volume fraction of magnetic particles and the mass fraction of surfactants

Magnetorheological fluids (MRFs) is composed of carbonyl iron (CI) powder distributed in carrier fluid. This paper studied the sedimentation behavior of MRFs in a cylindrical column by using direct visual observation (VO). In order to obtain the settlement law of MRFs with respect to particle concentration and surfactant contents, MRF samples with different particles volume fractions (i.e., 4, 10, 20 and 28 vol%) and with different surfactant mass fractions (i.e., none, 2, 4 and 5 wt%) were prepared, separately. And the commercial MRFs with the same magnetic particles volume fraction was used as the control group. In addition, the morphology of bare CI and surface modified CI particles samples were measured, experimentally, by light microscope. At last, three different settling velocity models (Vesilind model, Dick model, and Richardson and Zaki model) were considered to acquire the sedimentation velocity of magnetic particle concentration of MRF samples. Results present Dick model is more suited to the sedimentation rule of MRF sample in our study. The propagation velocity formula of the volumetric concentration of particles was also established on the basis of sedimentation velocity of particles and the particle setting velocity equation with the variational surfactant contents was also obtained.

Modeling and Analysis of the Influence of Costal Remediation and Repair Management Project on the Coastal Erosion and Siltation

ABSTRACT Zou, T., 2018. Modeling and analysis of the influence of costal remediation and repair management project on the coastal erosion and siltation. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 305–308. Coconut Creek (Florida), ISSN 0749-0208. In view of the problem that the modeling results of the current coastal erosion and siltation by using the current modeling mothed are not ideal, the modeling efficiency is low and the flexibility is poor, the modeling method of coastal erosion and siltation based on numerical simulation is proposed. The sediment transport equation is calculated by the critical shear stress, sediment carrying capacity and particle sedimentation velocity, and the numerical simulation results of the influence of costal remediation and repair management project on the coastal erosion and siltation are obtained according to the obtained parameters. According to the simulation results, the ...

High-Performance Magnetorheological Suspensions of Fe3O4-deposited Carbon Nanotubes with Enhanced Stability

AbstractThe magnetorheological (MR) performance of suspensions based on the Fe3O4-deposited carbon nanotubes (CNTs) was investigated by using a vibrating sample magnetometer (VSM) and a rotational rheometer. The Fe3O4-deposited CNTs were synthesized by the reduction process in which nano-Fe3O4 nanoparticles were generated and adsorbed on the surface of CNTs. All tested suspensions displayed excellent MR behaviors with high yield strengths. The morphology was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). It was revealed that Fe3O4 particles adsorbed on the surface of CNT particles led to make the surface topology bumpy and rough which decreased the particle sedimentation velocity. Finally, Turbiscan apparatus was used to test the sedimentation properties of Fe3O4-deposited CNTs suspensions. The suspensions showed excellent stability against sedimentation, much better than bare Fe3O4 particle suspension due to the inherent low density of CNT and its inside pore which can reduce the density mismatch between the nanoparticles and the carrier medium as well as the surface topology change due to the adsorption of Fe3O4.

A systematic approach for numerical research of realistic shaped particle-fluid interactions

The motion of rigid particles driven by gravity in a viscous fluid is relevant in many natural and industrial processes, and many investigations have been carried out on spheroidal particles. However, many non-spherical particles with complex surface structure exist in nature. So far, only few people have proposed an effective particle-laden flow model for practical engineering applications. Therefore, we put forward a set of models combined with the realistic shape data for practical engineering simulation. We present a systematic approach by researching the three-dimensional sedimentation of realistic shaped particles in a viscous fluid. The DEM-FDM method is used for numerical simulations. The morphology of particles is obtained by micro X-ray computed tomography. The novelty of our present contribution relies on the combination of the Monte Carlo Scheme with FDM to calculate the hydrodynamic force acting on the particles. In addition, a new procedure is proposed using overlapping spheres to reconstruct the particles' micro-morphology in three dimensions. We verify the numerical implementation of our approach and validate it against the analytical solution for ellipsoids in uniform shear flow derived by Jeffery, 1922. We investigate the sedimentation of realistic shaped particles separately and that of four particles with different morphologies in an incompressible fluid. The aspect ratio (AR) ranges from 1.2 to 2.2. The density ratio is 2.6. The results show that the path instability of sedimentation of realistic shaped particles with different morphologies occurs, but the behaviour of their sedimentation is closely related to the particles' AR. The sedimentation velocity of particles with sharp corners is obviously higher than that of flat particles, which have a relatively lower sphericity. For particles with higher AR, the phenomenon of ‘helical sedimentation’ appears. This paper provides an effective method to simulate the interactions of particles and their morphology in an incompressible fluid in engineering applications, with continuous improvements in computer performance.

The impact of particle shape on fall velocity: Implications for volcanic ash dispersion modelling

Modelling atmospheric volcanic ash dispersion is a critical tool in mitigating the impact of large explosive eruptions; it is also useful for understanding and reconstructing past events. Most atmospheric dispersion models include a sedimentation velocity term that is sensitive to the physical properties of the particle, but many do not use particle shape as an input parameter; instead particles are assumed to be spherical. There are many empirical and semi-empirical shape-dependent drag laws. We measure the velocity of scaled analogue particles over the range of flow conditions anticipated for volcanic ash dispersion to test published formulae against an independent dataset. We use a semi-empirical formula we determined to be accurate for non-spheres to investigate the sensitivity of the modelled transport of an ash cloud to particle shape, using the atmospheric dispersion model NAME and a shape parameter we measure for non-spherical ash particles from Katla volcano, Iceland. We find that model particle trajectories are sensitive to particle shape for particles >1–3 μm diameter; the sedimentation velocity of smaller particles is low compared to atmospheric vertical velocities. Sensitivity to shape increases with size such that 100 μm particles can travel 44% further from the source when they are highly non-spherical (sphericity = 0.5). Despite the sensitivity of the fall velocity of large particles to their shape, however, forecasts of distal ash concentration using particle size distributions of 0.1–100 μm and 0.1–250 μm show relatively good agreement between a spherical and non-spherical case for the first 36 h after an eruption. The vertical structure of an ash cloud is more sensitive to particle shape than the horizontal extent. Model particle trajectories are also sensitive to particle size, and we find a discrepancy between different particle size parameters for non-spherical ash: particle long axis L, used in cryptotephra studies, was on average twice the equivalent-volume sphere diameter dv, used in dispersion modelling, for tephra samples from Katla volcano, Iceland. This discrepancy in size measurements could explain the observed travel distance of large distal cryptotephra shards.

High-Performance Magnetorheological Suspensions of Pickering-Emulsion-Polymerized Polystyrene/Fe3O4 Particles with Enhanced Stability.

The magnetorheological (MR) performance of suspensions based on core-shell-structured foamed polystyrene (PSF)/Fe3O4 particles was investigated by using a vibrating sample magnetometer and a rotational rheometer. Core-shell-structured polystyrene (PS)/Fe3O4 was synthesized by using the Pickering-emulsion polymerization method in which Fe3O4 nanoparticles were added as a solid surfactant. Foaming the PS core in PS/Fe3O4 particles was carried out by using a supercritical carbon dioxide (scCO2) fluid. The density was measured by a pycnometer. The densities of PS/Fe3O4 and PSF/Fe3O4 particles were significantly lowered from that of the pure Fe3O4 particle after Pickering-emulsion polymerization and foaming treatment. All tested suspensions displayed similar MR behaviors but different yield strengths. The important parameter that determined the MR performance was not the particle density but rather the surface density of Fe3O4 on the PS core surface. The morphology was observed by scanning electron microscopy and transmission electron microscopy. Most Fe3O4 particles stayed on the surface of PS/Fe3O4 particles, making the surface topology bumpy and rough, which decreased the particle sedimentation velocity. Finally, Turbiscan apparatus was used to examine the sedimentation properties of different particle suspensions. The suspensions of PS/Fe3O4 and PSF/Fe3O4 showed remarkably improved stability against sedimentation, much better than the bare Fe3O4 particle suspension because of the reduced density mismatch between the nanoparticles and the carrier medium as well as the surface topology change.

Soil Particle Size Analysis by Laser Diffractometry: Result Comparison with Pipette Method

Soil texture as the basic soil physical property provides a basic information on the soil grain size distribution as well as grain size fraction representation. Currently, there are several methods of particle dimension measurement available that are based on different physical principles. Pipette method based on the different sedimentation velocity of particles with different diameter is considered to be one of the standard methods of individual grain size fraction distribution determination. Following the technical advancement, optical methods such as laser diffraction can be also used nowadays for grain size distribution determination in the soil. According to the literature review of domestic as well as international sources related to this topic, it is obvious that the results obtained by laser diffractometry do not correspond with the results obtained by pipette method. The main aim of this paper was to analyse 132 samples of medium fine soil, taken from the Nitra River catchment in Slovakia, from depths of 15-20 cm and 40-45 cm, respectively, using laser analysers: ANALYSETTE 22 MicroTec plus (Fritsch GmbH) and Mastersizer 2000 (Malvern Instruments Ltd). The results obtained by laser diffractometry were compared with pipette method and the regression relationships using linear, exponential, power and polynomial trend were derived. Regressions with the three highest regression coefficients (R2) were further investigated. The fit with the highest tightness was observed for the polynomial regression. In view of the results obtained, we recommend using the estimate of the representation of the clay fraction (<0.01 mm) polynomial regression, to achieve a highest confidence value R2 at the depths of 15-20 cm 0.72 (Analysette 22 MicroTec plus) and 0.95 (Mastersizer 2000), from a depth of 40-45 cm 0.90 (Analysette 22 MicroTec plus) and 0.96 (Mastersizer 2000). Since the percentage representation of clayey particles (2nd fraction according to the methodology of Complex Soil Survey done in Slovakia) in soil is the determinant for soil type specification, we recommend using the derived relationships in soil science when the soil texture analysis is done according to laser diffractometry. The advantages of laser diffraction method comprise the short analysis time, usage of small sample amount, application for the various grain size fraction and soil type classification systems, and a wide range of determined fractions. Therefore, it is necessary to focus on this issue further to address the needs of soil science research and attempt to replace the standard pipette method with more progressive laser diffraction method.

Sedimentation behavior of poly(methyl methacrylate) spheres in water upon application of a DC vertical electric field of the order of a few V/mm

Recently, our group discovered the phenomenon that the sedimentation velocity of colloidal particles in water increased drastically when a horizontal electric field of the order of a few V/mmDC was applied. The authors call this the electrically induced rapid separation (ERS) effect. Regarding the mechanism, it is highly plausible that the particles gather each other in the horizontal electric field. In this study, the sedimentation velocity of poly(methyl methacrylate) (PMMA) spheres in water under a vertical electric field of the order of a few V/mmDC was investigated via transmitted-light intensity measurement. When an upward electric field was applied, the sedimentation velocities of the spheres, whose zeta potential was negative, increased due to the electrophoretic migration toward the cell bottom. When a downward electric field was applied, the sedimentation of PMMA spheres was not observed for a prolonged time, and eventually some of the spheres adhered to the upper positive electrode, and the other spheres settled out in the bottom negative electrode. As a result, in the vertical electric field, rapid sedimentation by forming an aggregation of PMMA spheres has not been observed. These results indicate that the electrical double layers around the spheres play a crucial role in the ERS effect. It is clear that the direction of an electric field plays a crucial role in the ERS effect.

Determination of the Porosity of PLGA Microparticles by Tracking Their Sedimentation Velocity Using a Flow Imaging Microscope (FlowCAM)

PurposeTo investigate whether particle sedimentation velocity tracking using a flow imaging microscope (FlowCAM) can be used to determine microparticle porosity.MethodsTwo different methods were explored. In the first method the sedimentation rate of microparticles was tracked in suspending media with different densities. The porosity was calculated from the average apparent density of the particles derived by inter- or extrapolation to the density of a suspending medium in which the sedimentation velocity was zero. In the second method, the microparticle size and sedimentation velocity in one suspending fluid were used to calculate the density and porosity of individual particles by using the Stokes’ law of sedimentation.ResultsPolystyrene beads of different sizes were used for the development, optimization and validation of the methods. For both methods we found porosity values that were in excellent agreement with the expected values. Both methods were applied to determine the porosity of three PLGA microparticle batches with different porosities (between about 4 and 52%). With both methods we obtained microparticle porosity values similar to those obtained by mercury intrusion porosimetry.ConclusionsWe developed two methods to determine average microparticle density and porosity by sedimentation velocity tracking, using only a few milligrams of powder.