Sedimentation Motion Research Articles

Modeling coupled growth and motion of solid-air dendrite induced by convection in liquid hydrogen using phase-field lattice Boltzmann method

The safety hazard arising from the growth, condensation and accumulation of trace air in liquid hydrogen deserves attention. In order to predict the microstructural growth evolution and oxygen solute segregation distribution characteristics during solid-air dendrite motion induced by solution convection, a partially saturated bounce-back lattice Boltzmann coupled non-isothermal phase field method (PSLBM-PF) is proposed in this study. The partially saturated bounce-back lattice Boltzmann method (PSLBM) is employed to calculate the flow field and the forces and moments between the fluid and solid phases, and the phase field method (PF) is utilized for the computation of the growth of solid-air dendrites and the distribution of solute segregation. The motion of solid-air dendrites is determined by the momentum equation. The accuracy of the calculated interaction forces between fluid and solid phases was validated through the sedimentation process of circular particles in the liquid, and the capability of the present model to preserve the shape during solid-air dendrite motion (translational and rotational) was confirmed. Subsequently, this model was employed to investigate the growth and sedimentation motion of solid-air dendrites with different growth orientations in the solution. During dendrite settlement, the growth of the lower dendrite arms is promoted, while the settlement velocity and the solid phase fraction are almost unaffected by the growth orientation. Then, the differences in morphology evolution and solute distribution under conditions of forced convection for both stationary and motion are comparatively investigated, utilizing the free growth of solid-air dendrites under convection-free conditions as a reference. Finally, the model was utilized to study the growth of individual solid-air dendrites as well as translational and rotational motion under the action of shear flow. The presence of convection significantly alters the solute and temperature distributions at the solid-liquid interface, thereby influencing the dendrite growth process. The simulation results indicate that this model can predict the solid-air dendrites microstructural growth evolution and oxygen solute segregation distribution accompanying the convection and motion.

Study of sedimentation characteristics of an elliptical squirmer in a vertical channel

Abstract We used a two-dimensional lattice Boltzmann method to simulate the sedimentation motion of an elliptical squirmer in a vertical channel, taking into account the case of a circular squirmer, aiming to more realistically simulate the swimming of microorganisms in nature. The study in this was divided into two phases. The first phase comprised the numerical calculations of an elliptical squirmer with an aspect ratio of c = 2.0 and revealed three typical motion modes: steady inclined motion, wall-attraction oscillation, and large-amplitude oscillation. It was found that the formation of these three motion modes and transitions between modes are related to the pressure distribution formed between the elliptical squirmer and wall. In addition, significant differences exist between the motions of elliptical and circular squirmers. The force generated by the interaction between the elliptical squirmer and wall does not all point towards its center of mass, resulting in an additional torque on the elliptical squirmer; this is not the situation for the circular squirmer. The second phase of the study simulated squirmers with different aspect ratios (c = 1.0, c = 3.0). It was found that for an elliptical squirmer with an aspect ratio c = 3.0, the large-amplitude oscillation mode (among the above three motion modes) no longer exists. By combining the motion modes of a circular squirmer in the channel, it can be observed that as the aspect ratio c increases, the squirmer’s head direction tends to be more vertical, which may reduce the drag force during swimming.

Settling mode of a bottom-heavy squirmer in a narrow vessel.

The lattice Boltzmann-immersed boundary (IB-LB) method is used to numerically simulate the sedimentation motion of a single two-dimensional, bottom-heavy squirmer in a narrow vessel. The effects of the swimming Reynolds number Res = 0.1-3, eccentricity distance l = 0.15d-0.75d, and density ratio of squirmer to fluid γ = 1.1-2.0 on the settlement motion characteristics are investigated and analyzed. The results showed that four settling modes exist: vertical motion, unilateral oscillation, oscillation, and tilt. The bottom-heavy neutral squirmer and puller settle in the vessel during vertical motion when Res is 0.1-1.5. By increasing Res and swimming strength |β|, the bottom-heavy squirmer becomes more self-driven, shifting its settling mode from vertical motion to unilateral oscillation or oscillation. Increasing l or |β| does not affect the bottom-heavy neutral squirmer and puller's vertical settling mode but shifts the bottom-heavy pusher's settling mode from unilateral oscillation to oscillation or oscillation to unilateral oscillation. Similarly, altering γ or |β| has no impact on the eccentric neutral squirmer and puller's settling mode; however, pushers will switch from oscillation mode to attraction mode or from oscillation mode to tilt mode. Additionally, it was found that after the squirmer collided with the bottom wall, the bottom-heavy squirmer settled at the bottom of the vessel in a different state of motion.

Wall Effects for Spheroidal Particle in Confined Bingham Plastic Fluids

The wall effects on the sedimentation motion of a single spheroidal particle in cylindrical tubes filled with Bingham plastic fluid are investigated with the fixed computational domain using the Computational Fluid Dynamic (CFD) model in steady-state mode. The CFD model is validated with literature in both bounded and unbounded mediums. The rheological model of the Bingham plastic fluid is regularized with a smoothly varying viscosity. The retardation effects of the tube wall are presented in functions of Reynolds number Re, radius ratio λ (the radius of the tube to the semiaxis of the particle normal to the flow λ = R/r), aspect ratio E (the ratio of the semiaxis of the particle along the flow to r, E = b/r), and Bingham number Bn. The simulation results demonstrate that the drag coefficient C D declines with the rise in Reynolds number. The relative contribution to drag coefficient from the pressure force increases with larger Bingham number comparing with that from the friction force. The formation and size of the recirculation wake is suppressed by the yield stress. While Bn is approaching infinity, the limiting behavior is observed in the location of yield surface and the value of yield-gravity parameter. The values of critical yield-gravity parameter are explicitly given at different values of E, showing independence with Re and λ. For the flow with Bn ≥ 100, the influence of wall can be even ignored while λ is larger than 5.

Sedimentation motion of sand particles in moving water (I): The resistance on a small sphere moving in non-uniform flow

In hydraulics, when we deal with the problem of sand particles moving relative to the surrounding water, Stokes’ formula of resistance has usually been used to render the velocity of sedimentation of the particles. But such an approach has not been proved rigorously, and its accuracy must be carefully considered. In this paper, we discuss the problem of a sphere moving in a non-uniform flow field, on the basis of the fundamental theory of hydrodynamics. We introduce two assumptions: i) the diameter of the sphere is much smaller than the linear dimension of the flow field, and ii) the velocity of the sphere relative to the surrounding water is very small. Using these two assumptions, we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform, and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.

A Review of Dispersion Film Drying Research

Abstract Dispersion drying is an essential step in an enormous number of research and industry fields, including self-assembly, membrane fabrication, printing, battery electrode fabrication, painting, and large-scale solar cell fabrication. The drying process of dispersion directly influences the structure and properties of the resulting dried film. Thus, it is important to investigate the underlying physics of dispersion drying and the effects of different drying parameters. This article reviews modeling studies of coating drying processes, along with corresponding experimental observations. We have divided drying processes into two conceptual stages. In the first drying stage, liquid evaporation, particle sedimentation, and Brownian motion compete and affect the particle distribution during drying and thus in the final film structure. We have included a comprehensive discussion of the influences of drying parameters, such as evaporation rate, particle sizes, and temperature, on the above competition and the resulting film structure. A drying regime map describing where different drying phenomena dominate was formulated based on the literature. We also extended our discussion to the practical applications of battery slurry drying an essential step in conventional battery electrode manufacturing. In the second drying stage, the physics of porous drying and crack formation are reviewed. This review aims to provide a comprehensive understanding of dispersion drying mechanisms and to provide guidance in the design of film products with favorable structures and properties for targeted practical applications.

Container size effects on the validity for the concept of sedimentation turbulence studied using coagulated suspension of Na-montmorillonite in the semi-dilute regime

In our previously proposed concept of sedimentation turbulence, the feed-forward mechanism of flocculation induced by a sequential cohesive collision between settling flocs during the sedimentation process resulted in the monotonous increase of the settling velocity with increments of the settling cylinder height. However, the monotonous increase of the settling velocity and the size of flocs onset of the sedimentation turbulence are considered to meet across their limiting values. In order to confirm this conjecture, the effects of container sizes, i.e., the diameter and the height of the settling cylinder, on the validity of this concept were investigated on the basis of maximum floc size, which was maintained during the sedimentation process. The sedimentation experiments of highly coagulated Na-montmorillonite in the semi-dilute regime were extended using cylinders taller in height and smaller in diameter. The results obtained demonstrate that the maximum velocity becomes much faster than that of the free settling of a single floc. A notable observation was made when a cylinder with a diameter of 10 mm was used and in which the corresponding floc size was in the same order of magnitude. In this case, the clogged large floc essentially stopped its sedimentation motion. The crude estimation of the fluid force exerted on the floc during the sedimentation process was found to be consistent with this drastic change. • Sedimentation rate was enhanced by a collision of flocs resulted from a feed-forward mechanism. • The validity of sedimentation turbulence concept against the diameter and the height of the settling cylinder was examined. • Limiting behavior of sedimentation was found in the relation of cylinder diameter and size of developed flocs. • Crude estimation of the fluid force exerted on the floc was discussed.

Role of nanoparticles on critical heat flux in convective boiling of nanofluids: Nanoparticle sedimentation and Brownian motion

This study presents simulation of heat and mass transfer in two-phase flows of various nanofluids at various volume fractions and mass flow velocities. In contrary to most of research in the available literature, nanoparticles sedimentation along with Brownian motion of nanoparticles are comprehensively modeled and effects of these two important parameters on heat transfer and critical heat flux are evaluated. The aim of this modeling is to investigate the effect of nanoparticles and their sedimentation on the critical heat flux and mass transfer phenomena. All four mechanisms of mass transfer are simulated. The studied nanofluids are water-silver, water-copper, water-nickel and water-alumina with volume fractions of 1 to 5% and their results are compared against saturated water. Simulation of sedimentation together with Brownian motion of nanoparticles considerably improves the model precision. Nanofluids are seen to result in increased critical heat flux, heat transfer coefficient and net mass transfer. Moreover, the heat transfer coefficient and the critical heat flux are increased with the volume fraction of nanoparticles. Increase in mass flow velocity leads to rise of critical heat flux. In the event of nanoparticle sedimentation during the boiling process, the critical heat flux and heat transfer coefficient are seen to decrease.

Measurement of Average Aggregate Density by Sedimentation and Brownian Motion Analysis

The spatially averaged density of protein aggregates is an important parameter that can be used to relate size distributions measured by orthogonal methods, to characterize protein particles, and perhaps to estimate the amount of protein in aggregate form in a sample. We obtained a series of images of protein aggregates exhibiting Brownian diffusion while settling under the influence of gravity in a sealed capillary. The aggregates were formed by stir-stressing a monoclonal antibody (NISTmAb). Image processing yielded particle tracks, which were then examined to determine settling velocity and hydrodynamic diameter down to 1 μm based on mean square displacement analysis. Measurements on polystyrene calibration microspheres ranging in size from 1 to 5 μm showed that the mean square displacement diameter had improved accuracy over the diameter derived from imaged particle area, suggesting a future method for correcting size distributions based on imaging. Stokes' law was used to estimate the density of each particle. It was found that the aggregates were highly porous with density decreasing from 1.080 to 1.028 g/cm3 as the size increased from 1.37 to 4.9 μm.

Computational modeling of aerosol transport, dispersion, and deposition in rhythmically expanding and contracting terminal alveoli

Inhalation dosimetry in the alveolar region is critical in assessing health risks of inhaled toxicants and therapeutic outcomes of systemic pulmonary drug delivery. Most previous studies of acinar deposition focused on respiratory bronchioles or alveolated ducts with either steady unidirectional or tidal flow through the duct. The precise nature of particle dynamics in response to different wall motions of the blind-ended terminal alveoli is unclear. The objective of this study is to numerically investigate the flow and particle behaviors in terminal alveoli which rhythmically expand and contract at varying modes, frequencies, and amplitudes. Parametric study of physiological factors that affect alveolar deposition will be undertaken to gain a better understanding of relevant deposition mechanisms. Particle dispersion and rhythmic wall effect on alveolar deposition will be examined in the absence of gravity. An idealized terminal alveolus model was developed with rhythmically alveolar moving boundary conditions. The dynamic wall expansion mode and magnitude were based on experimentally measured chest wall motions and tidal volumes. Dimensional analysis was used to develop an alveolar deposition correlation. Results of this study show radical discrepancies in airflow kinetics in comparison to the alveolated duct. Recirculation zones that characterize the airflow in the alveolated duct are absent in the terminal alveolus. This study also demonstrates that the alveolar deposition is sensitive to the particle diameter, alveolar orientation, and breathing frequency, but is relatively insensitive to the breathing depth. The periodic alveolar wall motion leads to incremental particle dispersion, which was found to have a net effect in reducing particle deposition in the alveolus. A correlation was proposed for particle deposition in terminal alveoli that captured the separate contributions from the gravitational sedimentation and rhythmic wall motion.

Diversity and survival of artificial lifeforms under sedimentation and random motion.

Cellular automata are often used to explore the numerous possible scenarios of what could have occurred at the origins of life and before, during the prebiotic ages, when very simple molecules started to assemble and organise into larger catalytic or informative structures, or to simulate ecosystems. Artificial self-maintained spatial structures emerge in cellular automata and are often used to represent molecules or living organisms. They converge generally towards homogeneous stationary soups of still-life creatures. It is hard for an observer to believe they are similar to living systems, in particular because nothing is moving anymore within such simulated environments after few computation steps, because they present isotropic spatial organisation, because the diversity of self-maintained morphologies is poor, and because when stationary states are reached the creatures are immortal. Natural living systems, on the contrary, are composed of a high diversity of creatures in interaction having limited lifetimes and generally present a certain anisotropy of their spatial organisation, in particular frontiers and interfaces. In the present work, we propose that the presence of directional weak fields such as gravity may counter-balance the excess of mixing and disorder caused by Brownian motion and favour the appearance of specific regions, i.e. different strata or environmental layers, in which physical-chemical conditions favour the emergence and the survival of self-maintained spatial structures including living systems. We test this hypothesis by way of numerical simulations of a very simplified ecosystem model. We use the well-known Game of Life to which we add rules simulating both sedimentation forces and thermal agitation. We show that this leads to more active (vitality and biodiversity) and robust (survival) dynamics. This effectively suggests that coupling such physical processes to reactive systems allows the separation of environments into different milieux and could constitute a simple mechanism to form ecosystem frontiers or elementary interfaces that would protect and favour the development of fragile auto-poietic systems.

Embodied intersubjectivity, sedimentation and non-actual motion expressions

As part of a long-term project investigating the relevance of phenomenology for (cognitive) linguistics we analyse two central, interrelated concepts:embodied intersubjectivity(intercorporeality) andsedimentation. With respect to the first, we spell out a number of different intercorporeal structures, emanating at the most fundamental level from the dualLeibkörpernature of the body. Further, we demonstrate that sedimentation is more than a ‘geological metaphor’ as meaning is intrinsically layered in human experience. This is first illustrated by reviewing evidence from ontogenetic semiotic development within the framework of the Mimesis Hierarchy model (Zlatev 2013). Then, we focus on the linguistic construal of situations lacking actual motion in dynamic terms through expressions of non-actual motion such asThe road goes through the forestandHe was uplifted by her smile. We review studies of non-actual motion in Swedish, English, French, Bulgarian and Thai extending and re-formulating previous analyses. We argue that the present analysis is more adequate than cognitive linguistic explanations in terms of ‘mental simulation’ and ‘conceptual metaphor’. We conclude by pointing out how our phenomenological investigation can help resolve a number of classical dilemmas in semantics: Is language primarily grounded in the body or in society? Is the ontology of linguistic meaning mental or social? What is the relationship between pre-linguistic experiences and linguistic conventions?

Concurrent particle diffusion and sedimentation measurements using two-dimensional tracking in a vertical sample arrangement

This letter reports a method for simultaneous tracking of Brownian motion and superimposed sedimentation movement of multiple micro- and nanoparticles in liquid. Simple two-dimensional particle tracking can be employed because the thin liquid sample film is arranged vertically and viewed from the side with a dark field video microscopy setup. Therefore, both diffusion and sedimentation can be used for particle size calculation, allowing analyses over a wide range of sizes and mass densities. To validate the method, size distributions of reference particles with known density and diameters ranging from 100 nm to 6 μm were determined. Brownian motion for size calculation is useful for sufficiently small particles, whereas sedimentation can only be applied if there is significant settling motion superimposed on Brownian motion (which requires large diameters and/or densities). Within a certain range, both principles are suitable for size measurements. As a consequence, this method can be used to determine the size and density of unknown particles in a single measurement step, provided that they exhibit both sedimentation and diffusive motion.

Study on Particle Size and Concentration Using Laser Speckle Technique in Light Scattering Liquid Medium

A high coherent Laser beam is scattered from a colloidal medium of liquid (milk) due to the movement of sedimentation and Brownian motion and a random grainy image known as speckle pattern is formed in the observation plane. The resultant speckle having a statistical distribution of the intensity and it is dynamic in nature. Sequential laser speckle images were recorded for different concentrations and the time evolution of this interference image carries information about the dynamics of the scattering particles. The aim of this work is to evaluate the use of dynamic speckle for the assessment of particle size and corresponding speckle size for different concentration with the help of image processing technique.

Rayleigh–Bénard convection of Al2O3/water nanofluids in a cavity considering sedimentation, thermophoresis, and Brownian motion

This paper aims to investigate the Rayleigh–Bénard convection of Al2O3/water nanofluids in a cavity considering the sedimentation, thermophoresis, and Brownian motion. For this purpose, a numerical simulation is carried out using finite volume method to obtain the flow patterns and heat transfer characteristics of nanofluid flow inside the cavity. The results are presented for volume fractions up to 4%, Rayleigh numbers between 104 and 8×104 where the temperature difference between top and bottom walls is between 2 and 10°C. To validate the numerical solution, comparisons are made between the numerical results and experimental data available in the literature. The comparisons unfold that the results of numerical work are in a good agreement with the previous experimental results.

Geomorfologia y peligros de la subcuenca del rio Auqui (Calcayhuanca), Huaraz, Ancash

La parte baja de la subcuenca del río Auqui, entre los 3,200 y 3,500 msnm, comprende el área periférica y de expansión urbana de la ciudad de Huaraz. Son espacios tradicionalmente ocupados para desarrollar actividades agrícolas y ganaderas; sin embargo, en los últimos años debido al auge económico de Huaraz, el aludido espacio está siendo paulatinamente urbanizado. Esta parte baja de la cuenca son áreas naturales de sedimentación fluvioglaciar y de movimientos en masa (alud-aluviones). En la parte alta de la cuenca, la erosión glaciar y la fusión de la masa glaciar (deshielo) son el origen de los aludidos procesos naturales. La ocurrencia de alud-aluviones, que afectaría la parte baja de la cuenca, son lentos; sin embargo, no se descarta que ocurran en cualquier momento, similar al de 1941 o 1970, debido a que el Perú es un país altamente sísmico.

Natural spatial variability of algal endosymbiont density in the coralAcropora globiceps: a small-scale approach along environmental gradients around Moorea (French Polynesia)

This study provides a baseline describing natural small scale variability ofSymbiodiniumdensity in the sentinel coralAcropora globicepsduring the summer, under non-bleaching conditions. Spatial scales investigated range from the colony scale (1–10 cm, i.e. among branches of the same colony) to the reef scale (1–10 km, i.e. among stations distributed over several locations and depths), at Moorea Island, French Polynesia. The coral–Symbiodiniumsymbiosis is a key process in scleractinian coral physiology, andSymbiodiniumdensity provides an easy-to-measure and inexpensive biomarker of this symbiosis health. Spatial variability of three major environmental factors: light intensity, sedimentation and water motion was also assessed to evaluate their potential link withSymbiodiniumdensity. Density ofSymbiodiniumdid not significantly differ within colonies or among colonies within a station. However, a marked depth gradient was observed, showing increasing density with increasing depth and decreasing light intensity. These observations provide an interesting reference for forthcoming comparisons with disturbed conditions, such as bleaching events.

Analysis of latex, gold and smectite colloid transport and retention in artificial fractures in crystalline rock

The transport behavior of artificial (gold and latex) and natural (smectite) colloids within artificial fractures in natural crystalline rock was analyzed. The selected colloids presented different size, shape, density and surface charge: the effects of these parameters on their transport and retention in the fractures were evaluated in conjunction with the effects of the hydrodynamic characteristics of the system (water velocity/residence time in the fracture and fracture width). Resultshowed that, in crystalline rock fractures, all the analyzed colloids travel as fast as or faster than water (retardation factors, Rf≤1). Different parameters were identified to simultaneously control the velocity of colloids in the fracture, and an efficient analysis of Rf values could be performed relating them to the Taylor dispersion. This parameter accounts for the Brownian diffusion (colloid size), the mean water velocity and the fracture width.All the experiments were carried out under unfavorable electrostatic conditions (rock and colloids both negatively charged) and, in spite of clear exclusion effects observed, colloids were retained on the fracture surface. Under similar water velocities, the recovery of smectite colloids was always higher than that of latex and gold colloids, most probably due to the different morphology of the particles.Colloid retention was observed mainly in zone of the rock with defects, micro-fractures and grain boundaries and increased significantly as the water flow rate decreased. The retention behavior observed could not be totally explained considering only sedimentation and Brownian motion effects.

Investigation on the phase separation in undercooled Cu–Fe melts

On the basis of the gravity difference and the temperature dependence of the interfacial energy of the separated phases, the amalgamation of the droplets of minor phase was affected by Stokes sedimentation and Marangoni motion during the liquid-phase separation. Moreover, the velocity of Stokes motion increased distinctly with the undercooling, while the velocity of Marangoni motion was slightly impacted. At the beginning of the liquid-phase separation, the droplets of minor phase were dominated by Marangoni motion when the droplets radius was small. As the droplets radius increased by combination, the effect of Stokes sedimentation strengthened gradually. Additionally, the coagulation process was mainly controlled by Stokes sedimentation when a critical radius rd was far exceeded.

Study on dielectrophoretic deposition of airborne particles in a vertical micro channel

Airborne particles significantly contribute to the toxicity of environmental pollution. A mathematical model is developed and analyzed to study the dielectrophoretic deposition of airborne particles in a vertical micro channel. Finite element programs are utilized to calculate the air flow and potential distribution in the vertical micro channel. The electric field in the numerical solution space is obtained by employing a potential gradient in the x and y directions. The dielectrophoretic force and sedimentation motion of a spherical particle are achieved. The simulated results show that the dielectrophoretic force is maximal at the tips of the shorter electrode. The initial position of the particle, initial direction of the particle, radius of the particle, electrode dimension, applied voltage and air flow velocity are the main factors affecting the trajectories of airborne particles in a micro channel. Modification of the particle size distribution using the technology as a dielectrophoretic filter is more feasible in practice. Sedimentation micro channels in series with the shorter electrode on an alternating side will be beneficial to improve particle sedimentation efficiency.