Wetting Behaviors Of N-Hexadecane Nanodroplets Using Molecular Dynamics Simulation

In this paper,the molecular dynamics simulation method is used to study the wetting behavior of n-hexadecane nano-droplet on the smooth wall surface,rough wall surface,and PTFE wall surface and the wettability of the n-hexadecane-water mixed system using the LAMMPS software.The result of simulation shows that the wall length(width)and thicknessthe and number of n-hexadecane and cutoff radius have little influence on the equilibrium contact angle.With the increase of the potential energy of surface,the total energy gradually decreases and the equilibrium contact angle gradually decreases.For three kinds of potential energy surface,with the increase of temperature,the time required for the equilibrium gradually increases and the equilibrium contact angle gradually decreases.For the fencing form rough surface,as the roughness factor is gradually increased,the contact state of nanodrolet changed from Wenzel to Cassie.For the neutral wall surface,the equilibrium contact angle remains unchanged with the increase of the roughness factor.In the lyophilic wall surface,as the roughness factor is increased from 1.75 to 2.75,the equilibrium contact angle also gradually increases.As phase area fraction increase from 0.2 to 0.8,the equilibrium contact angles of the lyophobic wall surface and the lyophilic wall surface gradually decrease,while for the neutral wall surface,the equilibrium contact angle remains basically unchanged.For a square rough surface,when the roughness factor is less than critical value,the equilibrium contact angle of the wall surface under three kinds of potential energy increases.When the roughness factor is greater than critical value,the equilibrium contact angle of the droplet remains basically unchanged.For the lyophobic wall surface,the equilibrium contact angle increases first and then decreases with the width of the groove.For the neutral wall,the contact angle remains substantially constant with the groove width.For the lyophilic wall surface,the equilibrium contact angle increases with the groove width.While gradually decreasing,the sphericity of the droplets in the square cylinder shape is substantially close to 1.Moreover,the square columnar equilibrium contact angle is larger than the value of the barrier type equilibrium contact angle.In the simulation of n-hexadecane nano-droplets on the surface of PTFE,the equilibrium contact angle gradually increases with the increase of the number of molecules,and decreases gradually with the increase of the cut-off radius and temperature.When the roughness factor increases,the equilibrium contact angle gradually increases and the droplets transition from the lyophilic state to the neutral state.As the phase area fraction increases,the equilibrium contact angle increases first and then decreases.As the contact width increases,the droplet contact angle decreases.In the simulation study of n-hexadecane-water mixed system,when the number of water molecules increases,the equilibrium contact angle of n-hexadecane nano-droplets gradually increases.When the temperature increases,the equilibrium contact angle of n-hexadecane nano-droplets gradually increases.