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The settling dynamics of spherical and elliptical particles in a viscous Newtonian fluid are investigated numerically using a finite difference technique. The terminal velocity for spherical particles is calculated for different system sizes and the extrapolated value for an infinite system size is compared to the Oseen approximation. Special attention is given to the settling and tumbling motion of elliptical particles where their terminal velocity is compared with the one of the surface equivalent spherical particle.

The settling dynamics of cylinders in a viscous Newtonian fluid are investigated numerically using an iterative finite difference scheme, which uses a nonuniformly spaced staggered grid. Special attention is given to the details of the spatial discretization and how they influence the physical results. The terminal velocity is calculated for different system sizes and cylinder diameters and the extrapolated values for an infinite system size are compared with the Oseen approximation.

In the present work, we investigate the ability of recently proposed computational operators to characterize the problem of pattern formation by fluid flow and mass transport in a viscous binary fluid mixture under osmosedimentation. We perform a numerical investigation of these patterns using three computational operators (R² → R), computed from the spatial mass distribution, the streamlines, and the velocity fields. Our main goal is to demonstrate the ability of these computational operators to distinguish different dynamical regimes in the complex patterns arising from the osmosedimentation process.

We present a numerical method to deal efficiently with large numbers of particles in incompressible fluids. The interactions between particles and fluid are taken into account by a physically motivated ansatz based on locally defined drag forces. We demonstrate the validity of our approach by performing numerical simulations of sedimenting non-Brownian spheres in two spatial dimensions and compare our results with experiments. Our method reproduces qualitatively important aspects of the experimental findings, in particular the strong anisotropy of the hydrodynamic bulk self-diffusivities.

Magnetorheological model suspensions with different contents of iron particles have been investigated. The results show an increase of the shear stress by increasing the magnetic field and the solid content, which was mathematically modelled. The influence of the solid content is approximately exponential without magnetic field and linear in strong magnetic fields. The effect of the temperature and of the base oil viscosity on the shear stress is negligible in the field but decisive without field. The sedimentation behavior also strongly depends on the iron particle content, where MR fluids with a higher concentration settle with a lower intensity due to the higher sediment height. The response time of the magnetorheological model suspensions could not be clearly determined, but it is less than 10 milliseconds.

TiO₂ hierarchical structure composed of H₂Ti₃O₇ nanoribbons and TiO₂ anatase nanoparticles was synthesized via a two-step hydrothermal process, including the recrystallization of TiO₂ precursor into nanoribbons and the subsequent deposition of TiO₂ nanoparticles on nanoribbon surface. The coated nanoribbons exhibited a good photocatalytic activity to degrade Rhodamine B (RhB) with a kinetics constant of 0.0269/min, 10 times higher than that of the as-produced nanoribbon (0.0026/min). They also possess good sedimentation properties compared to the pristine TiO₂ anatase particles. The excellent photocatalytic performance together with sedimentation property makes these hybrid nanostructures effective and recyclable photocatalysts for wastewater treatment in industrial applications.

The simulation of the variation of the erosion or sedimentation and the sediment-carrying capability of the water on the river segments, as it changes from the lower-water season to the higher-water season, is performed by a dynamical model of the sediment transport on a river network. The model is constructed by considering that the sediment-carrying capability of the water in one segment is modulated by the undergone state of it and that of its neighbor segments. The calculated results can simulate the relative variations occuring in the natural river when the water seasons alternate.

The sedimentation measurement is of significant importance when designing and synthesizing magnetorheological (MR) fluid for engineering applications. Generally, visual observation is always used to discern the mud line position but knows nothing about the concentration distribution under the mud line. The method using electromagnetic scanning is limited by the position resolution because of the height of the inductor, and the method based on thermal conductivity is time-consuming and determines the sedimentation status at a specific location.

In this paper, the sedimentation behavior is revealed by the laser transmittance intensity (LTI) method which is based on scattering when the light passes through the MR fluid, the higher the concentration and the stronger the scattering, the weaker the received light intensity. Specifically, the laser diode and the photodiode were utilized as the light source and receiver, respectively.

MR fluid samples in a series of concentrations are used to obtain the correlation between volume fraction and photodiode output voltage, and that is taken as the calibration of the sensing method. In the experiments, the scanning with height and the sensing with time are jointly employed to characterize the settling process of a specific MR fluid.

We study the steady translational fall of a homogeneous body of revolution around an axis a, with fore-and-aft symmetry, in a second-order liquid at nonzero Reynolds (Re) and Weissenberg (We) numbers. We show that, at first order in these parameters, only two orientations are allowed, namely, those with a either parallel or perpendicular to the direction of the gravity g. In both cases the translational velocity is parallel to g. The stability of the orientations can be described in terms of a critical value E_c for the elasticity number E = We/Re, where E_c depends only on the geometric properties of the body, such as size or shape, and on the quantity (Ψ₁ + Ψ₂)/Ψ₁, where Ψ₁ and Ψ₂ are the first and second normal stress coefficients. These results are then applied to the case when the body is a prolate spheroid. Our analysis shows, in particular, that there is no tilt-angle phenomenon at first order in Re and We.

Polydisperse suspensions with particles of a finite number N of size classes have been widely studied in laboratory experiments. However, in most real-world applications the particle sizes are distributed continuously. In this paper, a well-studied one-dimensional kinematic model for batch sedimentation of polydisperse suspensions of small equal-density spheres is extended to suspensions with a continuous particle size distribution. For this purpose, the phase density function Φ = Φ(t, x, ξ), where ξ ∈ [0, 1] is the normalized squared size of the particles, is introduced, whose integral with respect to ξ on an interval [ξ₁, ξ₂] is equivalent to the volume fraction at (t, x) occupied by particles of that size range. Combining the Masliyah–Lockett–Bassoon (MLB) model for the solid-fluid relative velocity for each solids species with the concept of phase density function yields a scalar, first-order equation for Φ, namely the equation of the generalized kinetic theory. Three numerical schemes for the solution of this equation are introduced, and a numerical example and an L¹ error study show that one of these schemes introduces less numerical diffusion and less spurious oscillations near discontinuities than the others. Several numerical examples illustrate the simulated behavior of this kind of suspensions. Numerical results also illustrate the solution of an eigenvalue problem associated with the equation of the generalized kinetic theory.

In this paper we consider a two-dimensional viscous sedimentation model which is a viscous Shallow–Water system coupled with a diffusive equation that describes the evolution of the bottom. For this model, we prove the stability of weak solutions for periodic domains and give some numerical experiments. We also discuss around various discharge quantity choices.

While conducting a study with air in a simple closed rectangular cavity, we have discovered the formation of highly impressive, complex-structured, and symmetrical smoke density patterns. Using the box counting method the fractal characteristic of the patterns is demonstrated.

The homogeneous and substantial dispersion of nanoparticles into base fluids is vital since the final properties of any nanolubricant are estimated by their quality of stability. This paper addresses the effect of NiO nanoparticles dispersion into SN500 lubricant oil and its nonisothermal thermo stability. The dispersion of NiO nanoparticles is achieved by ultrasonication method. The thermo stability is estimated by Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). The result shows that the thermo stability of base fluid enhances up to 0.3wt.% particle concentration then it decreases due to agglomeration of dispersed nanoparticles. The findings recommend that 0.1wt.% and 0.3wt.% of NiO-nanolubricant can be used for the temperature-dependent applications up to 200^∘C.

For land creation regarding coastal structures, large mounds of soil, sand, and blocks are emplaced for mound formation, while accurate prediction of sedimentation deposition steps is necessary for cost reduction of construction work. In this study, high-resolution calculations using computational grids as fine as one to several tens with regard to typical block size are performed to ascertain details of flow fields around the blocks. The Smagorinsky model is introduced to investigate a turbulence field under high particle Reynolds number conditions. The deposition steps of block groups thrown into the water and the flow fields surrounding blocks that are difficult for measurements are presented in detail. Complex turbulent flow is formed in the sedimentation process and the influence of turbulence is not negligible.

This study presents a model which takes flocculation, sedimentation and turbulent diffusion into account, to analyze the vertical transport of cohesive fine sediment. A good agreement between simulation results and published experimental data shows the model can be used to describe vertical transport of cohesive fine sediment. We discuss the influence factors through simulation experiments. The results indicate sedimentation dominates in upper regions and later stage, flocculation plays more important role in lower regions and early stage, while the effect of turbulent diffusion is remarkable in whole region, especially in high turbulence energy dissipation rate.

The proposed formula for modeling sedimentation is based on a concept of hydrodynamic equilibrium in sediment transport. Hydrodynamic equilibrium occurs when the sediment transport is in a form of grain jumps with the distance traveled $dx$ smaller than the one established in the numerical modeling. A first-order upwind scheme FDM is applied. It provides the solution to equations describing changes in bathymetry in time and space coupled with simultaneous changes of bed sediment distribution. A clear-cut division of sediment transport into those during wave crest and wave trough is proposed. The results of bathymetry modeling coincided satisfactorily with the laboratory data. Moreover, the longer the experiments run, the more the results of measurements are compliant with the calculations. A certain time is needed for sediment transport to reach the hydrodynamic equilibrium, especially when the suspended load is significant. It is reached after going through the initial stages of bed level changes coupled with simultaneous changes of grain size distribution. The application of the model to field conditions shows its ability to predict sedimentation of dredged channels. Furthermore, the calculations show a good agreement with measured bed grain size distributions of sediment samples taken from the sites within the navigational channel of Łeba Port in Poland.

Wave forces during the 2004 Indian Ocean tsunami have caused morphological deformations of some coastal areas in Aceh, Indonesia. The sediment transport process during the tsunami wave propagation around near shore areas is a challenging numerical problem. To observe the coastal morphological changes after the Indian Ocean tsunami, this study numerically simulates the coastline changes, sedimentation and erosion areas, and seabed profiles changes around the Ulee Lheue Bay of Aceh, which was severely damaged by the tsunami. Two-dimensional horizontal areas were simulated by Cornell Multi-grid Coupled Tsunami (COMCOT) and Delft3D. Data of the nearshore area were collected from previous measurements acquired by the Indonesian Navy. According to the results, sediment in the sea area was deposited approximately 2.5km from the initial coastline, at the northern part of one small island occupying the Ulee Lheue Bay. This island reduced the energy of the tsunami waves during the backwash process, dumping a significant amount of eroded sediment near the coastline area.

The lung is an external organ forming the site of unwanted material or particles. In order to protect it, the airways have to be highly effective filters and if the particle deposit they need to be cleared. Inhaled particles can cause a variety of diseases. There are various factors on which the prediction of depositing particles depends, such as age, particle size, flow rate gender, the physics of the particles, the anatomy of the respiratory tract etc.

In many biodiversity rich watersheds, there is a lack of understanding concerning the trade-offs between timber harvesting and maintaining the watershed’s other ecosystem services, where losses of these services can occur as an externality from timber harvesting. As a result, the potential benefit from an appropriate mix of activities in multiple-use watersheds frequently remains unrealized. Our study provides insight into such trade-offs by estimating the value of a loss in a forest’s water purification/filtration service due to sedimentation caused by logging (the externality). More specifically, we develop a model to quantify the economic impact of increased sedimentation from forest roads on the quality of raw water withdrawn by a municipal water utility. Our approach is novel in several ways. First, we recognize the complex response of the water treatment plant to elevated sedimentation (turbidity) by considering a stochastic environmental influence on water system performance; to accommodate this complexity, we estimate the number of times turbidity exceeds an acceptable threshold by using a count data estimation procedure. Second, we generate alternative time series for turbidity that vary according to assumptions about forest management (logging versus no logging), traffic volume (road use intensity) and aggregate road length. We find that reductions in the economic value of the water purification/filtration service is more sensitive to traffic volume than other considerations but only when the road use is High, as the welfare effect in other cases is modest. Our analysis will be helpful to forest planners who must consider the trade-offs in forest management when timber harvesting can have harmful impacts on important ecosystem services, such as water purification/filtration.

After years of attempting to address rising turbidity in its water supplies with engineering solutions, Vitória, the capital of the Brazilian state of Espírito Santo, is turning to watershed conservation. Degradation in the watershed of the Santa Maria da Vitória River, from which Vitória obtains almost 40% of its water supplies, has resulted in a significant increase in water treatment costs; investments in improved filtration have only managed to slow. To reduce erosion in the watershed, a program of Payments for Environmental Services (PES) is being implemented, initially in a micro-watershed that has been identified as contributing disproportionately to sediment loads. This paper estimates the impact of watershed degradation on Vitória’s water treatment costs and undertakes a cost–benefit analysis of the benefits of watershed conservation. These interventions will benefit both downstream water users, in the form of lower water treatment costs, and upstream landholders, in the form of higher income from farming activities and payments for conservation.