Influence of surfactant kinetics on rapid interface creation via microjet impact on liquid pools

TL;DR

This study experimentally examines how different surfactant adsorption kinetics influence cavity dynamics during rapid interface formation caused by microjet impact, highlighting the importance of surfactant speed in dynamic surface tension reduction.

Contribution

It demonstrates the contrasting effects of surfactants with different adsorption kinetics on cavity behavior during rapid impact, using a harmonic oscillator model for analysis.

Findings

SDS shows negligible dynamic surface tension reduction during rapid impact.

Surfynol 465 enables deeper, longer-lasting cavities due to ultrafast adsorption.

The harmonic oscillator model accurately predicts cavity retraction and damping ratios.

Abstract

We experimentally investigate the influence of surfactant adsorption kinetics on cavity dynamics during the rapid formation of interfaces. For this purpose, we use a submillimeter jet impacting onto a surfactant-laden liquid pool much larger than the jet dimensions. Cavity retraction and closure occur on a submillisecond timescale, posing a stringent test of the ability of surfactants to reduce surface tension dynamically. Our experiments reveal the difference between the effects of sodium dodecyl sulfate (SDS), a surfactant with moderately fast adsorption kinetics, and Surfynol 465, a surfactant with ultrafast adsorption kinetics. For SDS, the collapse pathway is nearly indistinguishable from that of pure water, suggesting negligible dynamic surface tension reduction. In contrast, Surfynol allows the emergence of deeper cavities that persist longer in the liquid pool. The harmonic oscillator model accurately captures the cavity retraction in the deep seal regime. The fitted values of the damping ratios are consistent with the dynamic surface tensions.