Particle tracking for polydisperse sedimenting droplets in phase separation

TL;DR

This paper combines image processing and particle tracking to analyze droplet size and velocity during phase separation, revealing oscillatory behaviors and chaotic sedimentation in a binary fluid system.

Contribution

It introduces a method to simultaneously measure droplet size and velocity, enabling detailed analysis of sedimentation and oscillations in phase-separating fluids.

Findings

Droplets with radii of 4-40 micrometers are successfully tracked.

Droplet size distribution oscillates and couples with convective flow.

Sedimentation velocity exhibits chaotic behavior.

Abstract

When a binary fluid demixes under a slow temperature ramp, nucleation, coarsening and sedimentation of droplets lead to an oscillatory evolution of the phase separating system. The advection of the sedimenting droplets is found to be chaotic. The flow is driven by density differences between the two phases. Here, we show how image processing can be combined with particle tracking to resolve droplet size and velocity simultaneously. Droplets are used as tracer particles, and the sedimentation velocity is determined. Taking these effects into account, droplets with radii in the range of 4 -- 40 micrometers are detected and tracked. Based on this data we resolve the oscillations in the droplet size distribution which are coupled to the convective flow.