Particle motion in pressure-driven suspension flow through a symmetric T-channel

Abstract

Particle motion is studied in pressure-driven suspension flow through a bifurcating channel of square cross-section. Particles and suspending liquid are neutrally buoyant, i.e. of the same density ρ. Experimental particle trajectories are compared with the computed single-phase flow. The flow is in a symmetric T-junction, with each outgoing stream making a right angle relative to the incoming stream. All branches have the same cross-section and length, with L/D=29, where L is the length of each branch, and D is the side length. Particle trajectories are obtained by two-camera imaging for solid volume fraction 0 < ϕ ≤ 0.30. Inertia is characterized by the bulk, Re=ρDU/η, and particle scale Reynolds numbers, Rep=Re(d/D)2, where d is the diameter of the particles, U is the mean velocity in the inlet channel and η is the liquid viscosity. In this work, d/D=O(0.1) and Re=200. For the pure liquid, spiraling vortices are found in the outlet channels, emanating from near the bifurcation, and these flow structures are largely unchanged for ϕ ≤ 0.1, leading to spiraling motions of the particles. Particle tracks are compared against computed tracer motion in the pure fluid flow, and for dilute ϕ agree qualitatively well, with some deviation due to the particles’ finite size. For larger ϕ, the flow deviates strongly from that of pure fluid, keeping Re=200 based on the suspension effective viscosity. Vortices are damped for ϕ=0.2 and disappear for ϕ=0.30. Particle interactions with the wall and each other appear to dissipate energy at a higher rate than predicted by the effective viscosity.