Towards a general characterization of flat fan sprays through Direct Numerical Simulations

TL;DR

This paper uses Direct Numerical Simulations to analyze flat fan sprays, revealing different breakup regimes influenced by Weber number and opening angle, and proposes a simplified predictive model for spray behavior.

Contribution

It provides a comprehensive DNS-based characterization of flat fan spray regimes and introduces a simplified model for axial thickness evolution and breakup length prediction.

Findings

At low Weber numbers, thick rims retract at Taylor-Culick velocity.

At high Weber numbers, aerodynamic instabilities dominate disintegration.

The proposed model accurately predicts axial thickness evolution.

Abstract

A numerical investigation of flat fan sprays is conducted via Direct Numerical Simulations (DNS). Diverging liquid sheets are generated using tailored initial velocity profiles, where the opening angle serves as an explicit control parameter. The analysis reveals two distinct regimes: at low Weber numbers, the sheet features thick, retracting rims moving at the Taylor-Culick velocity, though rim-driven break-up is not observed without advanced techniques like Adaptive Mesh Refinement (AMR), At high Weber numbers, aerodynamic instabilities govern disintegration, with hole break-up absent in all cases. Representing the spray as a triangular sheet, a simplified model is proposed to predict the axial thickness evolution, showing good agreement with numerical measurements. The study also quantifies the influence of Weber number and opening angle on surface wave properties. An existing break-up length model is successfully applied, incorporating the present initial conditions, offering a predictive tool for future numerical and experimental studies.