Physics-informed sub-grid scale modeling of break-up of VOF simulations

Accurately predicting droplet size distributions in liquid atomization processes is crucial for many fields such as drug manufacturing, fuel combustion, and metal powder production. Standard Eulerian interface capturing methods such as Volume-of-Fluid (VOF) face challenges with numerical break-up of thin interfacial structures, since the smallest resolvable interfacial scale is controlled by the mesh size. Mesh-induced break-up prevents spray atomization simulations from reliably predicting droplet size distributions. Recently, the Reconstruction with 2 Planes (R2P) method has introduced the novel ability to represent and transport sub-grid scale films with arbitrarily small thicknesses without numerical break-up. In this work, we integrate R2P with a consistent volume-filtered framework for modeling the dynanics of sub-grid scale films. We propose a simple hole nucleation model based on a minimum film thickness criterion. Once a hole is formed, film retraction due to high-curvature rims is modeled using a Taylor–-Culick flow model. Finally, the resulting ligaments are identified and broken up using a model based on Rayleigh-Plateau instabilities. We test each sub-model in simple test cases, then deploy the full framework to simulate the aerobreak-up of a droplet. Finally, we explore application of this approach to more complex and realistic break-up scenarios.