Droplet Bag Formation in Turbulent Airflows

TL;DR

This paper uses numerical simulations to study how turbulent airflows cause liquid droplets to form bag-like structures, revealing the effects of turbulence on droplet morphology and breakup dynamics.

Contribution

It introduces a novel simulation approach to analyze droplet evolution in turbulent flows, highlighting turbulence effects on droplet shape, drag, and breakup mechanisms.

Findings

Turbulence increases droplet drag and causes flattening.

Droplets become tilted and corrugated under strong turbulence.

Turbulence intermittency influences droplet morphological evolution.

Abstract

We present novel numerical simulations investigating the evolution of liquid droplets into bag-like structures in turbulent airflows. The droplet bag breakup problem is of significance for many multiphase processes in scientific and engineering applications. Turbulent fluctuations are introduced synthetically into a mean flow, and the droplet is inserted when the air-phase turbulence reaches a statistically stationary state. The morphological evolution of the droplet under different turbulence configurations is retrieved and analysed in comparison with laminar aerobreakup results. While the detailed evolution history of individual droplets varies widely between different realisations of the turbulent flow, common dynamic and morphological evolution patterns are observed. The presence of turbulence is found to enhance the drag coefficient of the droplet as it flattens. At late times, the droplet becomes tilted and increasingly corrugated under strong turbulence intensity. We quantify these phenomena and discuss their possible governing mechanisms associated with turbulence intermittency. Lastly, the influences of liquid-gas viscosity ratio are examined and the implications of air-phase turbulence on the later bag film breakup process are discussed.