Lateral migration of spherical particles in porous flow channels: application to membrane filtration

1984 ◽  
Vol 39 (2) ◽  
pp. 343-355 ◽  
Author(s):  
F.W. Altena ◽  
G. Belfort
Author(s):  
Arman Pazouki ◽  
Dan Negrut

The current work promotes the implementation of the Smoothed Particle Hydrodynamics (SPH) method for the Fluid-Solid Interaction (FSI) problems on three levels: 1- an algorithm is described to simulate FSI problems, 2- a parallel GPU implementation is described to efficiently alleviate the performance problem of the SPH method, and 3- validations against other numerical methods and experimental results are presented to demonstrate the accuracy of SPH and SPH-based FSI simulations. While the numerical solution of the fluid dynamics is performed via SPH method, the general Newton-Euler equations of motion are solved for the time evolution of the rigid bodies. Moreover, the frictional contacts in the solid phase are resolved by the Discrete Element Method (DEM), which draws on a viscoelastic model for the mutual interactions. SPH is a Lagrangian method and allows an efficient and straightforward coupling of the fluid and solid phases, where any interface, including boundaries, can be decomposed by SPH particles. Therefore, with a single SPH algorithm, fluid flow and interfacial interactions, namely force and motion, are considered. Furthermore, without any extra effort, the contact resolution of rigid bodies with complex geometries benefits from the spherical decomposition of solid surfaces. Although SPH provides 2nd order accuracy in the discretization of mass and momentum equations, the pressure field may still exhibit large oscillations. One of the most straightforward and computationally inexpensive solutions to this problem is the density re-initialization technique. Additionally, to prevent particle interpenetration and improve the incompressibility of the flow field, the XSPH correction is adopted herein. Despite being relatively straightforward to implement for the analysis of both internal and free surface flows, a naïve SPH simulation does not exhibit the efficiency required for the 3D simulation of real-life fluid flow problems. To address this issue, the software implementation of the proposed framework relies on parallel implementation of the spatial subdivision method on the Graphics Processing Unit (GPU), which allows for an efficient 3D simulation of the fluid flow. Similarly, the time evolution and contact resolution of rigid bodies are implemented using independent GPU-based kernels, which results in an embarrassingly parallel algorithm. Three problems are considered in the current work to show the accuracy of SPH and FSI algorithms. In the first problem, the simulation of the transient Poiseuille flow exhibits an exact match with the analytical solution in series form. The lateral migration of the neutrally buoyant circular cylinder, referred to as tubular pinch effect, is successfully captured in the second problem. In the third problem, the migration of spherical particles in pipe flow was simulated. Two tests were performed to demonstrate whether the Magnus effect or the curvature of the velocity profile cause the particle migration. At the end, the original experiment of the Segre and Silberberg (Segre and Silberberg, Nature 189 (1961) 209–210), which is composed of 3D fluid flow and several rigid particles, is simulated.


2014 ◽  
Vol 749 ◽  
pp. 320-330 ◽  
Author(s):  
Kazuma Miura ◽  
Tomoaki Itano ◽  
Masako Sugihara-Seki

AbstractThe inertial migration of neutrally buoyant spherical particles in square channel flows was investigated experimentally in the range of Reynolds numbers ($\mathit{Re}$) from 100 to 1200. The observation of particle positions at several cross-sections downstream from the channel entrance revealed unique patterns of particle distribution which reflects the presence of eight equilibrium positions in the cross-section, located at the centres of the channel faces and at the corners, except for low $\mathit{Re}$. At $\mathit{Re}$ smaller than approximately 250, equilibrium positions at the corners are absent. The corner equilibrium positions were found to arise initially in the band formed along the channel face, followed by a progressive shift almost parallel to the side wall up to the diagonal line with increasing $\mathit{Re}$. Further increase in $\mathit{Re}$ moves the corner equilibrium positions slightly toward the channel corner, whereas the equilibrium positions at the channel face centres are shifted toward the channel centre. As the observation sites become downstream, the particles were found to be more focused near the equilibrium positions keeping their positions almost unchanged. These lateral migration behaviours and focusing properties of particles in square channels are different to that observed in microchannels at lower $\mathit{Re}$ and to what would be expected from extrapolating from the results for circular pipes at comparable $\mathit{Re}$.


Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 277
Author(s):  
Tohme Tohme ◽  
Pascale Magaud ◽  
Lucien Baldas

Understanding the behavior of a single particle flowing in a microchannel is a necessary step in designing and optimizing efficient microfluidic devices for the separation, concentration, counting, detecting, sorting, or mixing of particles in suspension. Although the inertial migration of spherical particles has been deeply investigated in the last two decades, most of the targeted applications involve shaped particles whose behavior in microflows is still far from being completely understood. While traveling in a channel, a particle both rotates and translates: it translates in the streamwise direction driven by the fluid flow but also in the cross-section perpendicular to the streamwise direction due to inertial effects. In addition, particles’ rotation and translation motions are coupled. Most of the existing works investigating the transport of particles in microchannels decouple their rotational and lateral migration behaviors: particle rotation is mainly studied in simple shear flows, whereas lateral migration is neglected, and studies on lateral migration mostly focus on spherical particles whose rotational behavior is simple. The aim of this review is to provide a summary of the different works existing in the literature on the inertial migration and the rotational behavior of non-spherical particles with a focus and discussion on the remaining scientific challenges in this field.


Author(s):  
Byung Rae Cho ◽  
Young Won Kim ◽  
Jung Yul Yoo

Lateral migration of particles has drawn a lot of attention in suspension community for the last 50 years. Since there is no need for extra external forces, lateral migration of particles plays an important role in constructing microfluidic devices in diverse engineering applications. In this paper, an experimental study on lateral migration of neutrally-buoyant spherical particles transported through a square microchannel is carried out using a fluorescent microscope at low Reynolds numbers. Fluorescent microspheres with diameters of d = 6 μm, 10 μm, and 16 μm are adopted as the test particles, which yield channel-to-particle size ratios of 13.3, 8 and 5, respectively. Spatial distributions of the particles in dilute suspension are visualized at different Reynolds numbers. It is shown that particles are uniformly distributed over the channel cross-section at relatively low Reynolds numbers. As the Reynolds number increases, however, particles migrate inward from the wall and away from the central axis of the channel, so that consequently they accumulate at an equilibrium position, exhibiting the so-called “tubular pinch effect”, first observed by Segre´ and Silberberg as early as in 1962. Experimental results obtained in this work offer design rules for microfluidic channels that play important roles of particle separation or particle focusing.


Author(s):  
Daniel UGARTE

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.


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