The objective of this research project is to assess and enhance the ability of a recently-advanced high-fidelity modeling framework for spray formation to model complex liquid break-up and predict drop size distributions in high viscosity and non-Newtonian liquid atomization systems, such as found in spray drying applications. This framework, dubbed enhanced Volume of Fluid (eVOF), was developed by the PI’s research group and hinges on two key components: (1) a fully conservative Eulerian interface capturing technique with the ability to capture sub-grid scale liquid features such as thin films and thin ligaments, known to be of critical importance in the break-up of viscous and non-Newtonian fluids, and (2) simple physics-based break-up models to convert these thin liquid features into spray droplets that can be tracked in a Lagrangian fashion.
In the first year of the project, non-Newtonian constitutive models were implemented and tested in the PI’s research flow solver, and shown to influence spray formation in simple flow configurations. Moreover, a simple pressure-swirl configuration was explored to demonstrate the ability of eVOF to preserve thin liquid films and virtually eliminate numerical break-up. In year 2, the non-Newtonian constitutive models were further refined and validated against bubble rise experiments. A realistic pressure-swirl nozzle was selected for study based on availability of nozzle geometry and drop size measurements. Despite the complexity of the resulting flow, eVOF was again shown to preserve sub-grid scale liquid films successfully. Advances were made on sub-grid scale modeling of film and ligament break-up, allowing preliminary comparisons of drop sizes against experiments to be shown.
Going forward, the sub-grid scale modeling of film and ligament break-up will be further improved, in particular in the limit of high-viscosity liquids, and a more comprehensive comparison of drop sizes will be made against experiments.