Particle transport in flow through a ratchet-like channel

Biomicrofluidics, 2009

Pressure-driven transport of particles through a symmetric converging-diverging microchannel is studied by solving a coupled nonlinear system, which is composed of the Navier-Stokes and continuity equations using the arbitrary Lagrangian-Eulerian finite-element technique. The predicted particle translation is in good agreement with existing experimental observations. The effects of pressure gradient, particle size, channel geometry, and a particle's initial location on the particle transport are investigated. The pressure gradient has no effect on the ratio of the translational velocity of particles through a converging-diverging channel to that in the upstream straight channel. Particles are generally accelerated in the converging region and then decelerated in the diverging region, with the maximum translational velocity at the throat. For particles with diameters close to the width of the channel throat, the usual acceleration process is divided into three stages: Acceleration, deceleration, and reacceleration instead of a monotonic acceleration. Moreover, the maximum translational velocity occurs at the end of the first acceleration stage rather than at the throat. Along the centerline of the microchannel, particles do not rotate, and the closer a particle is located near the channel wall, the higher is its rotational velocity. Analysis of the transport of two particles demonstrates the feasibility of using a converging-diverging microchannel for passive ͑biological and synthetic͒ particle separation and ordering.

2006

The lateral migration of a single spherical particle in tube Poiseuille flow is simulated by ALE scheme, along with the study of the movement of a circular particle in plane Poiseuille flow with consistent dimensionless parameters. These particles are rigid and neutrally buoyant. A lift law se s s

International Journal of Multiphase Flow - INT J MULTIPHASE FLOW, 2007

International Journal of Modern Physics C, 2009

The transport of particles in two-dimensional self-affine rough channels is investigated through numerical simulations. We show how the average transit time depends on the particle Stokes number as well as on the restitution coefficient controlling the collisions with the walls. More precisely, our results reveal that the particle motion in such irregular channels displays a complex behavior that is characterized by the existence of four distinct transit time regimes. Finally, we also show that this rich behavior is a direct consequence of the local competition between particle-structure (collisions) and particle-fluid (drag) interactions taking place in the system.

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016), 2016

The method of Dissipative Particle Dynamics is applied to investigate the effect of the parameters employed to model the presence of periodic rectangular wall roughness on planar nanochannel flow. The parameters considered here include the fluid/wall interactions, the range of interaction of fluid particles and wall particles (cut-off radius), the external applied force and the coarse-graining parameter (number of atoms per DPD particle). Protrusions of upper wall are modeled by periodically spaced rectangular protruding elements. The dependence of flow pattern on protrusion length and the amplitude of these parameters is investigated. The computed macroscopic quantities of practical interest include density, velocity, and pressure fields. Fluid particle localization near the solid wall is affected by the conservative force and the cut-off radius. Fluid velocity reduces as the protrusion length decreases for constant parameters and reduces as both the conservative force and the cutoff radius increases. The pressure is uniform across most of the channel and their pattern near and inside the cavities depend on the protrusion shape, the conservative force and cutoff radius. For the coarse graining parameter, the density and pressure remain almost constant in the core of the channel and their pattern near and inside the cavities depends on the protrusion shape.

Physical Review Applied

Journal of Serbian Society for Computational Mechanics

Transport of small particles, of micrometer and sub-micrometer size, by fluid occurs in many technological and biological systems. The channels through which the fluid flows are often with cross-sectional dimensions on the order of several to tens of micrometers. The aim of this study was to investigate effects of shape of micro-and nano-particles on particle trajectories when particles are transported within small channels as blood vessels. Efficiency of therapeutics by particles as the drug carriers is significantly dependent on particle trajectories. It is desirable to have particle trajectories approaching the vessel walls in order to increase therapeutic efficacy. We studied motion of particles in channels (pipes) for two physical conditions: Poiseuille flow, which is characteristic in pipe flow, and shear flow. Shear flow conditions are analyzed since the character of fluid flow near the wall in these systems can be approximated as shear, with a linear change of velocity with the distance from the wall. We here investigated trajectories of particles of different shapes in 2D flow using the finite element (FE) method, with a strong coupling approach for solid-fluid interaction and a remeshing procedure. The results give insight into the characteristics of the particle motion, e.g. trajectories and rotations, under various flow conditions in micron size channels, including flow in the presence of moving deformable discs. We demonstrate that the particle trajectories are essentially parallel to the wall for various conditions and that particle size and shape do not considerably alter the parallel nature of the trajectories.

Brazilian Journal of Chemical Engineering, 2007

In this work, the pneumatic conveying of non-spherical isometric particles with different degrees of non-sphericity is studied. The solids mass loading fraction is small enough in order to have a dilute flow, so inter-particle collisions can be neglected. As a first approximation, only the aerodynamic drag force acting on the particles is considered, neglecting the lift forces and the particle rotation. The drag coefficient is calculated using the correlations of and . The numerical simulations are compared with experimental data in a narrow six meters long horizontal channel flow laden with quartz and duroplastic particles with mean diameters of 185 and 240 µm, respectively (Kussin, 2004).

2005

The motion of small particles through different types of asymmetric potential landscapes has become a growing topic leading to different types of microdevices and nanodevices. 1–17 Also, these might provide a deeper understanding of several biological systems eg, ion-channel transport18, 19 in cell membranes.

Physica A-statistical Mechanics and Its Applications, 2006

The interaction of moving fluids with particles is still only understood phenomenologically when the Reynolds number is not vanishing. I will present three different numerical studies all using the solver ''fluent'' which elucidate this issue from different points of view. On one hand, I will consider the case of fixed particles, i.e., a porous medium and present the distribution of channel openings, fluid velocities and fluxes. These distributions show a scaling law in the density of particles and for the fluxes follow an unexpected stretched exponential behavior. The next issue will be filtering, i.e., the release of massive tracer particles within this fluid. Interestingly, a critical Stokes number exists below which no particles are captured and which is characterized by a critical exponent of 1 2 . Finally, I will also show data on saltation, i.e., the motion of particles on a surface which when dragged by the fluid performs jumps. This is the classical eolian transport mechanism responsible for dune formation. The empirical relations between flux and wind velocity are reproduced and a scaling law of the deformed wind profile is presented. r