Numerical Study of Consecutive Drop/Wall Impacts Using Smoothed Particle Hydrodynamics

Abstract

A fundamental understanding of drop/wall interactions is of vital importance to many engineering applications, particularly in internal combustion engines; the outcomes of drop/wall interactions directly affect an engine's overall performance. Numerical models developed for drop-wall interactions are mostly based on the impact of a single drop on dry or wet walls. To accurately mimic and model real engine conditions, it is necessary to have a comprehensive study of drop/wall interactions with consecutive droplets. A theoretical splashing criterion based on the K parameter incorporating the impingement frequency is presented in this paper. In this study, a numerical method, based on Smoothed Particle Hydrodynamics (SPH), is used to simulate the impact of a droplet train on a heated wall at different impingement frequencies. The present SPH method is validated against the experimental results on the propagation of the crown rim's diameter as a function of the non-dimensional time. Impact regimes are identified for various impact conditions based on the study of the time evolution of the post-impingement process. In this work, simulations were conducted for n-heptane drops at different impingement frequencies and diameters. It is found that the K parameter provides a better prediction for the impingement outcomes and the effect of impingement frequency is seen as the kinematic discontinuity among the spreading lamellae, film formation, and rapidness of drop impact. Additionally, the inhibition by high ambient pressure on the crown rim propagation is also quantified. The results of this study can be used to further improve spray/wall interactions models at realistic engine conditions.