Evaluating Surface Film Models for Multi-Dimensional Modeling of Spray-Wall Interaction

Surface film formation is an important phenomenon during spray impingement in a combustion chamber. The film that forms on the chamber walls and piston bowl produces soot post-combustion. While some droplets stick to the wall surface, others splash and interact with the gas present inside the combustion chamber. Accurate prediction of both the film thickness and splashed mass is crucial for surface film model development since it leads to a precise estimation of the amount of soot and other exhaust gases formed. This information could guide future studies aimed at a comprehensive understanding of the combustion process and might enable development of engines with reduced emissions. Dynamic structure Large Eddy Simulation (LES) turbulence model implemented for in-cylinder sprays [1] has shown to predict the flow structure of a spray more accurately than the Reynolds-averaged Navier-Stokes turbulence model. Therefore, using dynamic structure LES turbulence model to analyze the interaction of turbulent gas phase region with the liquid deposited as film and with the splashed droplets is a promising area to study turbulent multiphase flows interacting with a solid surface. Three dimensional Computational Fluid Dynamics (CFD) simulations were carried out in OpenFOAM to compare multiple surface film models (Stanton-Rutland [2], O’Rourke-Amsden [3] and Bai-Gosman [4]) working with the LES dynamic structure turbulence model on the basis of experimental results of properties such as, splash penetration, film thickness and film area. It was found that for different properties, some surface film models performed better than the others. A comparison was made based on a model’s overall ability to predict all the aforementioned properties accurately.