Particle Sedimentation In Fluids Research Articles

The effects of channel width on particle sedimentation in fluids using a coupled lattice Boltzmann-discrete element model

Understanding particle settlement in channeled fluids has wide applications, such as fine particulate matter, coronavirus particle transport, and the migration of solid particles in water. Various factors have been investigated but few studies have acknowledged the channel's effect on settlement dynamics. This study developed a coupled interpolated bounce-back lattice Boltzmann-discrete element model and examined how a channel's width affects particle settlement. A factor k denoting the ratio of the channel's width and the particle diameter was defined. The terminal settling velocity for a single particle is inversely proportional to k, and the time that the particle takes to reach the terminal velocity is positively related to k. When k is greater than 15, the channel width's effects are negligible. For dual particles of the same size, the drafting-kissing-tumbling (DKT) process occurs infinitely in a periodic pattern, with the two particles swapping positions and settling around the channel's centerline. The smaller the k, the sooner the DKT process occurs. The particles collide with the channel wall when k <= 10. For dual particles of different sizes, the DKT process occurs once so that the bigger particle leads the settlement. Both particles settle along the channel's centerline in a steady state. The bigger the k, the bigger the difference in their terminal settling velocities until k = 15. The small particle collides with the channel wall if released under the big particle when k = 6. The findings of this study are expected to inform channeling or pipeline design in relevant engineering practices.

Centrifuge 2.0

The centrifugation of samples is frequently required in laboratory analysis, whether be it for chemical, physical or biological analysis of soil. The software Centrifuge 1.0 is a simple tool available that enable researchers to quantify the energy applied to samples during the centrifugation process. This study aims to demonstrate the new option of calculus incorporated into the software, such as sedimentation of particles in fluids in the centrifuge and analyses the deviation on outputs caused by variations in the values of the parameters used. In its 2.0 version, the Centrifuge software is more useful in carrying out laboratory techniques, because it can be applied to quantify energy in samples or sedimentation of solids particles in fluids during the centrifugation process. The software Centrifuge 2.0 is freely available and can be obtained with the authors.

Sedimenting sphere in a variable-gap Hele-Shaw cell

We have measured the trajectory and visualized the wake of a single sphere falling in a fluid confined between two closely spaced glass plates (a Hele-Shaw cell). The position of a sedimenting sphere was measured to better than 0.001d, wheredis the sphere diameter, for Reynolds numbers (based on the terminal velocity) between 20 and 330, for gaps between the plates ranging from 1.014dto 1.4d. For gaps in the range 1.01d–1.05d, the behaviour of the sedimenting sphere is found to be qualitatively similar to that of an unconfined cylinder in a uniform flow, but our sedimenting sphere begins to oscillate and shed von Kármán vortices forRe>200, which is far greater than theRe= 49 for the onset of vortex shedding behind cylinders in an open flow. When the gap is increased to 1.10d–1.40d, the vortices behind the sphere are different – they are qualitatively similar to those behind a sphere sedimenting in the absence of confining walls. Our precision measurements of the velocity of a sedimenting sphere and the amplitude and frequency of the oscillations provide a benchmark for numerical simulations of the sedimentation of particles in fluids.

Dynamic simulation of a stochastic model for particle sedimentation in fluids

This paper studies various aspects of a stochastic model for particle sedimentation in fluids originally proposed by Pickard and Tory. A model-fitting procedure based on first-passage times is presented and estimators for all relevant parameter functions are given. Computational issues of a working implementation of the model for dynamic simulation are also addressed.

On a stochastic model for particle sedimentation in fluids

AbstractThe engineering sciences have long been interested in models describing the settling (or sedimentation) of particle ensembles in viscous fluids. From a theoretical point of view, sedimentation constitutes a two phase many‐body phenomenon with complex interaction and as such has proved to be quite inaccessible to modelling attempts with relevance in applications. A stochastic model was introduced by Pickard and Tory in 1977 and was subsequently revised. In this paper we expand and refine the stochastic model and present a satisfactory model‐fitting procedure and parameter estimators based on transit times of sedimenting particles.

The one-sided barrier problem for an integrated ornstein-uhlenbeck process

The first-passage problem is considered for the process where V(s) is an Ornstein-Uhlenbeck process with an additive constant term μ friction parameter β, and variance σ2 starting from V(O)=μ+μ Global explicit analytic approximations to the first-passage density are derived for the case of a one-sided fixed barrier at distance x from X (0). By a series of simulations the quality of these approximations is studied for varies χ,ν,β,μ,σ2. We also consider an application to stochastic models for particle sedimentation in fluids where the first-passage problem of an integrated Ornstein-Uhlenbeck process naturally arises.