SIMULATION OF THE LIQUID COUETTE FLOW IN A NANO-CHANNEL WITH DIFFERENT WETTABILITY

The relation between characteristics of solid surfaces and properties of destiny, velocity and slip in a nanochannel with different wettabilities is explored, using molecular dynamics simulation (MDS). In these simulations, the liquid Couette flow confined between two infinite parallel planar walls is considered, and statistical ensemble is set as NVT, and the interaction between atoms is calculated using Lennard-Jones potential energy function. The hydrophobic wall which is set to rigid surface is characterized by the low solid-liquid relative energy parameter. For all simulations, velocity-rescale method is used to keep the temperature constant and the Verlet algorithm is used to solve the Newton equations. Some conclusions are presented from the simulation results in this paper. Firstly, fluid density profiles which are adjacent to solid surfaces oscillate around the value of major fluid density, and the extents of oscillation decay, the periods of oscillation remain unchanged with the hydrophobicity increase of the solid surface. Secondly, greater hydrophobic walls lead to larger slip velocity, and the hydrophilic surface even leads to negative slip. Thirdly, slip velocity increases with the accretion of velocity of the solid surface in Couette flow, and accretion of slip velocity is accelerated greatly when the flow is in layer regime. Besides, we also find the superhydrophobic walls generate smaller slippage than hydrophobic walls, which varies from the common conception, and we explain this result basing Young's equation.