Numerical investigation of channel blockage by flowing microparticles

Abstract

a b s t r a c tThe dynamic formation of 3D structures of microparticle aggregates blocking the flow through straight microchannels is investigated by direct numerical simulation of the coupled motion of particles and fluid. We use the Force Coupling Method to handle simultaneously multibody hydrodynamic interactions of confined flowing suspension together with particle-particle and particle-wall surface interactions leading to adhesion and aggregation of particles. The basic idea of the Force Coupling Method relies on a multipole expansion of forcing terms (added to the Navier-Stokes equations) accounting for the velocity perturbation induced by the presence of particles in the fluid flow. When a particle reaches the wall or an attached particle, we consider that the adhesion is irreversible and this particle remains fixed. We investigate the kinetics of the microchannel blockage for several solid volumetric concentrations and different surface interaction forces. Many physical quantities such as the temporal evolution of the bulk permeability, capture efficiency, modification of the fluid flow and forces acting on attached particles are analyzed. We show that physical-chemical interactions, modeled by DLVO forces, are essential features which control the blockage dynamics and aggregate structure. IntroductionThe physics of transport, deposition, detachment and reentrainment of colloidal particles suspended in a fluid are of major interest in many areas of fluids engineering: fouling of heat exchangers, contamination of nuclear reactors, plugging of filtration membranes and occlusion of human veins, deposits in microelectronics and in the paper industry. In many solid/liquid separation processes such as micro-filtration or ultrafiltration of water, the limitation of the process performance is related to the fouling of filtration devices. To prevent or control the occurrence of fouling, it is necessary to achieve a better understanding of the respective roles of physical-chemical phenomena and hydrodynamic interactions in a confined suspension of particles. Non-hydrodynamic surface interactions and the adhesion of particles onto solid surfaces are the essential features to be modeled. However, mainly because of a complex interplay between the hydrodynamics of the flow, the physical-chemical properties of the filtered suspensions (often in a colloidal state) and the nature of the solid material, predicting fouling dynamics is still challenging.Different experimental techniques and numerical approaches have been developed to achieve new insights on the local structure of particle aggregates and the kinetics of blockage. Sharp and Adrian [4], by means of experiments in microtubes, observed blockage due to arch formation. The experiments were performed using liquids seeded with polystyrene beads at low volumetric concentration. They showed that a stable balance between the hydrodynamic forces and contact forces (mainly solid friction) between particles and the wall provokes the formation of arches. Wyss et al.[5] stu...

Numerical investigation of hard-gel microparticle suspension dynamics in microfluidic channels: Aggregation/fragmentation phenomena, and incipient clogging

“…Variations in the average velocity profile due to large aggregate formation on the walls have been also reported [16,17]. More recently, the formation of 3D microparticle aggregates during the flow of a suspension through a straight microchannel was also investigated by the force-coupling numerical method [18]. This method automatically (if not rigorously) accounts for inter-particle hydrodynamic interactions.…”

“…A DLVO force has been implemented to model adhesive, attractive and repulsive inter-particle interactions. Simulation results show that, depending on the interparticle inter-particle repulsive forces, aggregates can initially form near the wall and progressively clog the channel, or aggregates can form in the bulk of the fluid [18].…”

Dynamics of pore fouling by colloidal particles at the particle level

“…In our experiments we suppose that there is a direct capture of a particle when it deposits at a distance greater than 1.5D, surface to surface, from an immobile particle already inside the pore. Indeed once a particle gets immobilized it modifies the flow around it over a distance we estimate to be around 1.5D from its surface [31]. However here we do not provide any hydrodynamic treatment of the clogging process but instead we give simple rules for the building up of a clog ( Figure 10).…”

Preliminary modeling of overspray particles sedimentation at heat recovery unit in spray booth

“…There are conducted researches on sedimentation of particles in turbulent flow [2,5]. A stochastic model of particles deposition and clogging of ventilation duct was proposed in four elementary stages [3]: deposition, resuspension, agglomeration and clogging.…”

“…Mathematical and simulation models of sedimentation of particles on the inner walls of the channels in turbulent flow are presented in [2,3] and [5]. This article presents a preliminary mathematical and simulation model of overspray sediments growth.…”