纳米结构中浸入特性的非平衡分子动力学模拟

Non-equilibrium molecular dynamics simulation of the influence of nanostructures on water infiltration characteristics

为明晰复杂纳米通道内流体流动规律,采用分子动力学方法研究压力驱动作用下不同润湿性纳米通道的液态水浸入特性。建立液态水/不同润湿性纳米通道的非平衡态分子动力学模型,研究驱动压大小、壁面润湿性及纳米粗糙元结构对液态水浸入特性的影响规律。模拟结果表明:相同驱动压条件下,液态水易于浸入亲水性纳米结构通道内,相比于光滑纳米通道,纳米粗糙元结构凸显液态水的表面张力作用,提高液态水持续浸入纳米通道的驱动压;纳米粗糙元结构对液态水浸入速度以及密度分布均有影响,纳米粗糙元距离入口处越近,浸入过程的阻力越大,即液态水浸入纳米通道内的体积通量越小,研究结果为明晰复杂纳米通道内液态水输运的微观机理提供理论基础。

To clarify the law of fluid flow in a complex nanochannel, the molecular dynamics method was employed to investigate the infiltration characteristic of pressure-driven droplet into the nanochannel with different wettability. The nonequilibrium molecular dynamics model of liquid water/nanochannel with different wettability was established to study effects of driving pressure, surface wettability, and nanoscale roughness on infiltration characteristics. The simulation results indicated that droplets more rapidly entered into the hydrophilic nanochannel than the hydrophobic nanochannel under an identical driving pressure. And compared to the smooth nanochannel, effects of the surface tension of the droplet was obvious due to the structures of nanoscale roughness. Simultaneously, it could be found that the nanoscale roughness had a certain impact on both droplet infiltration velocity and density profiles. As the distance between the nanoscale roughness and nanochannel entrance decreased, the flow resistance in the infiltration process of droplets improved. It suggested that the volumetric flux of the infiltration of water into the nanochannels was reduced. The findings could provide a theoretical basis for uncovering the transport mechanism of liquid water in the complex nanochannel.