Collective transport of droplets through porous media

TL;DR

This paper investigates how droplets collectively move through porous media, revealing that their interactions can enable flow under conditions where single droplets would be trapped, with implications for various applications.

Contribution

It introduces a new understanding of collective droplet transport in porous media and derives conditions and rules governing this behavior.

Findings

Collective droplet flow occurs even when single droplets are trapped.

Flow increases pressure differences, enabling droplets to pass through pores.

Derived a Bond number and a rule for collective droplet flow.

Abstract

The flow of deformable particles, such as droplets, dragged by a fluid, through a network of narrow pores inside rocks or other porous media is key in a range of applications, from enhanced oil recovery and water filtration to lab on a chip sorting of cells. The collective dynamics and its impact on the flow are poorly understood. Here, using droplets as a prototype, we show that collective transport can occur for conditions under which a single particle would get trapped at a pore channel. When a series of droplets gets trapped, the fluids flow is affected significantly, leading to an increase of the pressure difference across the pore channels, which in turn squeezes the particles through the channels. We analyze the conditions for a single droplet to flow through one pore and derive the corresponding Bond number. We also obtain a rule for the collective flow of droplets in porous media.