Transition from clogging to continuous flow in constricted particle suspensions

Abstract

When suspended particles are pushed by liquid flow through a constricted channel, they might either pass the bottleneck without trouble or encounter a permanent clog that will stop them forever. However, they may also flow intermittently with great sensitivity to the neck-to-particle size ratio D/d. In this Rapid Communication, we experimentally explore the limits of the intermittent regime for a dense suspension through a single bottleneck as a function of this parameter. To this end, we make use of high time-and space-resolution experiments to obtain the distributions of arrest times (T ) between successive bursts, which display power-law tails (∝T −α ) with characteristic exponents. These exponents compare well with the ones found for as disparate situations as the evacuation of pedestrians from a room, the entry of a flock of sheep into a shed, or the discharge of particles from a silo. Nevertheless, the intrinsic properties of our system (i.e., channel geometry, driving and interaction forces, particle size distribution) seem to introduce a sharp transition from a clogged state (α 2) to a continuous flow, where clogs do not develop at all. This contrasts with the results obtained in other systems where intermittent flow, with power-law exponents above two, were obtained.

Intermittent flow and transient congestions of soft spheres passing narrow orifices

“…The nature of this discontinuous flow makes it difficult to define avalanche sizes for the soft, low-friction grains at narrow orifice sizes, since there is no clear definition of what can be considered a clog. A similar problem was discussed by Hidalgo 57 and Souzy 45 in the context of colloidal systems.…”

“…Similar intermittent clogging was recently reported in suspensions of non-Brownian microparticles. 45 The authors suspect that these clogs are dissolved by flow through interstices of the blocking particles.…”

“…26,29 It was also shown that non-adhesive colloidal particles in suspension flow across constrictions in a way that is very similar to the behavior of dry non-cohesive granular materials. 44,45 Silo discharge of hard grains has been investigated in numerous studies in the past, yet in agriculture, pharmacy and many technological processes, one frequently encounters soft particles. Nevertheless, soft granular material has been investigated only scarcely so far.…”

The effect of particle shape on discharge and clogging

“…There is rapid clogging by simultaneous arrival at d o /d < 3 and intermittent clogging at d o /d > 3 and Φ i = 0.25, indicative of bridge destabilization and particle accumulation. For comparison, intermittent clogging of spherical particles during particle-laden fluid flow has been observed for 3 < d o /d < 4 35,36 .…”

Size-dependent particle migration and trapping in three-dimensional microbubble streaming flows

“…Note that the approach provides particle size sorting by z position in addition to the already established separation in y [30,36] in a setup providing throughput in x. This could be of particular interest for constricted microfluidic systems in which solid particles are prone to clog the flow due to sieving of large particles or arching [37][38][39]. Future work will be dedicated to understand the role of inertial forces in the long-term migration observed in these systems and to analyze the role of density mismatch.…”