Spreading Behavior of Single Oil Droplet Impacting Surface with/without a Thin Liquid Film

When oil droplets impact a solid surface for oil-air lubrication, they may spread out to produce a thin oil layer on the surface, which serves as a significant source of lubrication. A test rig was constructed in this research to observe the spreading behavior of oil droplets impacting surfaces from both frontal and lateral views. From the frontal view, laser-induced fluorescence techniques are used to measure the thickness of the oil layer quantitatively during the spreading of oil droplets. While the lateral view can observe the shape evolution of the droplets. Oil droplet spreading patterns on the sheet with dry surfaces and with different thin liquid film thicknesses were studied, and the effect of viscosity and the thickness of the thin liquid film on spreading radius and spreading thickness is considered. The experimental findings demonstrate that the maximum spreading factor, the spreading central layer thickness, and the apparentness of retraction all increase as viscosity increases. The retraction is obviously impacted by thin liquid films, and the retraction weakens as the thin liquid film thickness increases.

Automated summary

A test rig was constructed to study the spreading behavior of oil droplets impacting solid surfaces. Quantitative measurements of the oil layer thickness during droplet spreading were made using laser-induced fluorescence techniques from the frontal view, while the shape evolution of the droplets was observed from the lateral view. The study investigated the spreading patterns on dry surfaces and surfaces with different thin liquid film thicknesses, considering the effects of viscosity and film thickness. The results showed that increased viscosity led to increased spreading factor, central layer thickness, and retraction, while thicker liquid films weakened retraction.