Exploring the Weber dependency of jet fragmentation: a Direct Numerical Simulation investigation

TL;DR

This study uses Direct Numerical Simulation to analyze jet fragmentation across different Weber numbers, comparing theoretical models and revealing self-similar droplet phase space characteristics independent of Weber number.

Contribution

It provides a comprehensive DNS investigation of jet fragmentation over a range of Weber numbers, comparing models and analyzing droplet phase space normalization.

Findings

Droplet size and velocity distributions are characterized.

Theoretical models are compared for near-nozzle droplet size prediction.

Droplet phase space normalization reveals self-similarity independent of Weber number.

Abstract

Jet fragmentation is investigated through a Direct Numerical Simulation campaign using Basilisk (Popinet & collaborators 2013). The simulations span over one order of magnitude of gaseous Weber numbers (13 to 165), i.e. over the second wind-induced and atomization regimes, and the jets develop over distances up to 28 nozzle diameters. The study focuses on the size and velocity distributions of droplets, as well as their joint distribution. Two models derived from different theoretical backgrounds, the statistical description of the turbulence intermittency (Novikov & Dommermuth 1997) and the empirical description of the ligament-mediated fragmentation (Villermaux et al. 2004), are compared for describing the droplet size distribution close to the nozzle. The characteristics of the size-velocity joint distribution are explained using the vortex ring theory (Saffman 1992) which highlights two sources of fragmentation. Finally, the joint histogram of the particulate Reynolds and Ohnesorge numbers is analysed and a normalisation is suggested. It reveals that the delimitations of the droplet phase space, once properly normalised, are self-similar and independent of the gaseous Weber number, both numerically and experimentally.