Clogging and avalanches in quasi-two-dimensional emulsion hopper flow

TL;DR

This study investigates how quasi-two-dimensional emulsions flow through a hopper, revealing a transition from intermittent avalanches to continuous flow influenced by flow rate and system compliance, with implications for understanding clogging phenomena.

Contribution

It introduces a computational model with system compliance that reproduces experimental avalanche and flow behaviors in emulsion hopper flow.

Findings

Avalanches follow a power law distribution of exit intervals.

Flow transitions smoothly from avalanches to continuous flow with increasing strain rate.

Compliance in the model is key to reproducing experimental flow behaviors.

Abstract

We experimentally and computationally study the flow of a quasi-two-dimensional emulsion through a constricting hopper shape. Our area fractions are above jamming such that the droplets are always in contact with one another and are in many cases highly deformed. At the lowest flow rates, the droplets exit the hopper via intermittent avalanches. At the highest flow rates, the droplets exit continuously. The transition between these two types of behaviors is a fairly smooth function of the mean strain rate. The avalanches are characterized by a power law distribution of the time interval between droplets exiting the hopper, with long intervals between the avalanches. Our computational studies reproduce the experimental observations by adding a flexible compliance to the system. The compliance results in continuous flow at high flow rates, and allows the system to clog at low flow rates leading to avalanches. The computational results suggest that the interplay of the flow rate and compliance controls the presence or absence of the avalanches.