Molecular dynamics simulation of microscopic droplet spread on rough surfaces

This study uses molecular dynamics simulations to elucidate the spreading b ehaviour of a liquid droplet oil a rough solid surface. The Lennard-Jones p otential energy model is adopted as the interaction model between the liqui d and the solid molecules. The paper considers two typos of rough surface: periodic and random. These surfaces are characterized by their roughness he ight and their spatial variation. For a periodic surface, the roughness hei ght is defined by the amplitude, A, while for a random surface, it is defin ed in terms of the standard deviation of the roughness height, sigma. Regar ding the spatial variation of the surface, a periodic surface is characteri zed by the wavelength, lambda, while the random surface is characterized by its autocorrelation length, L. Simulation results indicate that the charac teristics of the rough surface can significantly influence spreading behavi our, in terms of final equilibrium time, spreading radius, and spreading to pography. It is observed that the effects of roughness height and spatial v ariation are broadly similar for both periodic and random surfaces. It is f ound that increasing roughness height and decreasing spatial periodicity bo th prolong the final equilibrium time, and that the filial spreading radius decreases with increasing roughness height and increases with larger spati al periodicity.