The Characteristics Of Liquid Poiseuille Flow By Molecular Dynamics Simulation

The fluid flow in the micro channel has been widely applied in many fields such as industries, bio-engineering and electronic information technology. With the development of the micro/nano science and technology in recent ten years, such as MEMS/NEMS and biochips, the research in microscale is becoming more of concerns. Because the characteristic size is very small, the microfliud has great different flow characteristics from the macrofluid. At present, the mechanisms of microfliud flow are not yet clear, and some problems have been encountered many of in practices. Among the researches, the problems of the slippage and the drag reduction at a solid surface are especially important. We also still can't precisely measure the relationship between slippage and wettability which is a main factor to the micro-fliud because of lacking of conditions. Molecular Dynamics Simulation, as a methold of molecular simulation, has an incomparable advantages compared with traditional experimental and theoretical methods in studying microfliuds on microscale.In this paper, based on Fluid Mechanics and Molecular Dynamics Simulation, the influence of the wettability on the poiseuille flow on microscale were investigated as follows:Firstly, the developments of microflow and the differenct characteristics from macroflow were introduced; and some of the concepts and models related to the content of our research were emphasized, such as the wettability, the slippage, the slip length. The more detailed introduction was given to the basic principles, processes and methods of molecular dynamics simulations. Secondly, by using the Molecular Dynamics Simulation, the droplet static shape were simulated on different wettability panells.Then, Molecular Dynamics simulation was applied to study the phenomenon of the liquid argon flow between two parallel plane walls acted by the external force and different wettability boundaries. The effects of different wettability boundary to the liquid flow, the flow rate and the distribution of particles were investigated. The results show that it is easily observed the velocity slippage on the hydrophobic surface, while layered orderly distribution of the liquid particles near the hydrophilic surface. It was possible to have small slippage on the surface whose hydrophilic is not so strong, but has little effect on the flow. At last, by using analytic method, we got the velocity formula and flow rate formula of fluid between two parallel plate with the slip boundry in the case of the laminar flow. And the conclusions were compared with the simulation results.Finally the relationship between wettability and threshold pressure were investigated. The results of simulation show that the flow need a external force which was known as threshold pressure to overcome the resistance caused by the strong hydrobolic surface when theliquid flows through it.