Predicting primary and secondary breakup is a key challenge in many applications ranging from medical aerosol delivery to cleaner propulsion systems. Knowledge of the droplet size distribution is crucial for all subsequent processes. Combining Volume-of-Fluid (VoF) and Lagrangian Particle Tracking (LPT) can capture the entire spray breakup process, but their vastly different spatial and temporal resolution requirements pose a major computational challenge.

This challenge kept us quite busy in the last few years, and I am happy to report that we have made progress.

Large eddy simulation based seamless VOF-LPT approach for describing atomization and evaporation processes: Application to jets in crossflow

- A PhD-Thesis by Yaquan Sun

Method: This study builds on previous work by enhancing the Eulerian-Lagrangian hybrid model, seamlessly integrating Volume of Fluid (VOF) and Lagrangian Particle Tracking (LPT) to capture the entire liquid fuel jet atomization and evaporation process. Adaptive Mesh Refinement (AMR) is employed to optimize computational cost while preserving accuracy, particularly at liquid-gas interfaces. Furthermore, the approach accounts for evaporation at both the dispersed droplet phase and the gas-liquid interface, addressing a key limitation of previous studies.

Key Findings:

• Instabilities & Breakup Modes: Identified and categorized breakup regimes for water and Jet A, with and without evaporation.
• Vortex Behavior: Evaporation led to less defined vortices and more dispersed fields due to intensified breakup at higher temperatures.
• Jet Penetration: Water jets penetrate further than Jet A, with temperature affecting breakup length more than penetration.
• Evaporation Rate: Jet A evaporates faster than water, leading to a quicker reduction in liquid mass flux.
• Droplet Dynamics: Evaporation didn’t significantly affect droplet velocity but reduced the Sauter mean diameter, aligning with experimental data.