The Dynamic Simulation Of The Wettability Of A Water Droplet On A Solid Surface

Wettability of liquid on the solid surface is a common phenomenon. It not only has an important effect on condensation heat transfer, but also affects fluid flows apparently. Especially for the case of micro/nano scale, wettability is much more significant in many researches. This wetting phenomenon can be quantified by the contact angle of liquid droplet on a solid surface. At present, many measuring methods for contact angle have been found. The molecular dynamic simulation used here has attracted much attention for its fairly accurate. Meanwhile, it can obtain information of molecular level such as molecular structure and interaction, so that it is convenient to analyze influential factors of contact angle in depth.The primary flow of molecular dynamic simulation has been studied. First, establish the simulation system and set up the initial conditions. Chose a suitable force filed and then calculate forces acting on each molecule and intermolecular potential according to this force filed expression, then each molecule’s coordinate and velocity at the next step can be figured out. After equilibrium of the system, many macroscopic properties and basic laws can be obtained. The key steps in the simulation course are choosing potential function and establishing initial system. In this article, all the files the molecular dynamic simulator NAMD needed have been analyzed according to the simulation flow, including contents and main parameters.The simulation of liquid SPC/E has been developed at first. After analyze simulation system in detail, all the files needed have been established. When the system reached equilibrium status, the mass density and the radical distribution functions of the liquid have been calculated. It has been found that the results computed from our simulation are in good agreement with experimental data and results from others’simulation. After that, SPC/E and Pt model systems with different conditions have been simulated. Similarly with the simulation of SPC/E, all the files needed have been established, including files about initial molecular location, initial molecular velocity, forces acting on each molecule and simulation parameters. After reached balance, the method extracting simulation results and calculating contact angles has been introduced in detail, and it has been used to calculate contact angles in this simulation. The results show that the contact angles of SPC/E on a Pt model were affected dramatically by interaction force between solid and liquid. Original shape and original radius of the droplet were also important influential factors, while temperature was a trivial factor.