Flows of concentrated suspensions through an asymmetric bifurcation

Abstract

Flows of concentrated suspensions at low Reynolds number through an asymmetric T-junction bifurcation composed of rectangular channels are studied experimentally using nuclear magnetic resonance imaging. In contrast to the unequal division of a uniform concentration material, the suspension and the neutrally buoyant, noncolloidal particles are almost equally partitioned between downstream branches, and motion of particles across the dividing stream surface is deduced to occur at the bifurcation. We attribute the rearrangement of particles to enhanced spreading of high concentration ͑and therefore high local viscosity͒ regions of the suspension toward the side branch. The partitioning is accompanied by lateral asymmetry in the concentration and velocity profiles of the downstream branches, although the inlet profiles are symmetric. In the spanwise direction, inhomogeneous concentration distributions that develop upstream persist throughout the inlet and downstream channels. Overall, the fractions of the flow rate and cross-sectional area flowing into the side branch vary slightly with bulk particle volume fraction. Also, inertial effects likely cause an observed shift of the dividing streamline toward the side branch as the flow rate increases, while the flow rate and particle flux fractions entering the side branch hardly change. Finally, directional asymmetry is observed between diverging and converging flows.

Shear-induced particle migration in three-dimensional bifurcation channel

“…To the best of our knowledge there are no experimental and simulation studies on flow of concentrated suspensions in symmetric three dimensional Y shape bifurcation channels that are common in microfluidic devices. In this work, we have studied In a previous study on migration in asymmetric T-junction bifurcation channel (Ahmed and Singh, 2011) the predictions from diffusive flux model were found to be in good agreement with the experiments of Xi and Shapley (2008). Thus, for simplicity of implementation, and economy of computations we have chosen diffusive flux model in our present study.…”

“…They observed that the particles are almost equally partitioned in downstream branches even though the flow partitioning is unequal. Later, Ahmed and Singh (2011) performed numerical simulations based on the diffusive flux model and obtained good agreement with the experimental work of Xi and Shapley (2008).…”

“…The flow physics of concentrated suspensions of small particles relative to channel width is less studied numerically and experimentally despite their wide application. Xi and Shapley (2008) have performed NMR experiments on flow of concentrated suspensions through asymmetric T-junction bifurcation channel of rectangular cross-section. They observed that the particles are almost equally partitioned in downstream branches even though the flow partitioning is unequal.…”

Numerical design of a T-shaped microfluidic device for deformability-based separation of elastic capsules and soft beads

“…Interparticle interactions become dominant in concentrated suspensions, and, at low confinement, particles are almost equally divided between the downstream branches regardless of flow rate ratios [14].…”

Separation of particles in non-Newtonian fluids flowing in T-shaped microchannels

“…Volume excluded effects in the inlet channel, due to the existence of a zone near the channel wall unaccessible to the particles, and particle-wall hydrodynamic interactions are responsible for this different partitioning at bifurcations [16]. Several studies have addressed the role of particle deformability [17][18][19][20], concentration [21][22][23][24] and shape of bifurcation [16,24] on the fluid-particle partitioning. Finally, the enrichment/depletion of particles in the two outlet streams has been proposed as an effective mechanism to design simple microfluidic devices for particle separation [16], fractionation [16] and filtering [15].…”