Size Amplification of Jet Drops due to Insoluble Surfactants

When a bubble bursts at a liquid-air interface, the resulting cavity collapses and the capillary waves focus to form a jet. The jet can pinch to form drops, which are commonly referred to as jet drops. Jet drop formation due to bubble bursting has been well studied for interfaces without contamination. In reality, surface-active agents (surfactants) are often found on liquid-air interfaces. We propose a general, systematic method to quantitatively compare between experiments and direct numerical simulations of the Navier-Stokes equations for surfactant-sensitive flows by using experimentally-derived surface tension isotherm measurements in the numerical simulation. We find that for bubbles without precursor capillary waves (low La, a Reynolds number), the ejected drop radii decrease upon the addition of insoluble surfactants, opposite to the trend previously observed (Constante-Amores et al. 2021 JFM, Pierre et al. 2022 PRF, Pico et al. 2024, Vega and Montanero 2024 ETFS) for bubbles with precursor capillary waves (high La). A physical explanation is given.

Jun Eshima and Tristan Aurégan contributed equally to this work.