Splashing Criterion and Topological Features of a Single Droplet Impinging on the Flat Plate 2018-01-0289

This paper aims to provide the experimental and numerical investigation of a single fuel droplet impingement on the different wall conditions to understand the detailed impinging dynamic process. The experimental work was carried out at the room temperature and pressure except for the variation of the impinged wall temperature. A high-speed camera was employed to capture the silhouette of the droplet impinging on wall process against a collimated light. Water, diesel, n-dodecane, and n-heptane were considered as four different droplets and injected from a precision syringe pump with the volume flow rate of 0.2 mL/min at various impact Weber numbers. The impingement outcomes after droplet impacting on the wall include stick, spread, rebound and splash, which depend on the controlling parameters of Weber number, Reynolds number, liquid and surface properties, etc. In this paper, the various splashing and non-splashing criteria were summarized based on the earlier research and applied to evaluate the current experimental data. It is found that the experimental results at various conditions overall show good agreement in predicting the splashing and non-splashing phenomena with existing droplet-wall interaction models. A new correlation of deposition-splashing in terms of the current experimental data is developed. Further, the effects of the impact Weber number, surface temperature, and surface roughness on the time evolution of droplet spreading factor, height ratio, the dynamic contact angle, and the contact line velocity were studied to aid in the development of a dynamic contact angle model. Finally, the volume of fluid (VOF) method was considered to characterize the single fuel droplet impinging on the wall and provide a better understanding of the dynamic impingement process in the CONVERGE™ framework. The simulation results of the spreading factor, height ratio, and the contact angle match well with the experimental results during the droplet impingement process.