微通道中纳米颗粒的输运、沉积和吸附研究

With the development of nanotechnology, the transport, deposition and adsorption of nanoparticles in microchannel have attracted wide attention. Their application spread throughout the areas of energy, environment, human health and high-tech industry. When the scale of microchannel is very small, the flow characteristic length will be close to gas molecular mean free path (for ideal gas about 70 nm), or the liquid will be put in a limited space near molecular scale (for water about 5 nm), surface-area-to-volume ratio become very large, the microscale effects on the whole flow, like interfacial effect, the interactions between molecules etc., cannot be ignored anymore. At the same time, the transport and dynamics characteristics of nanoparticles will be very different from large-scale particles. The molecular dynamics simulation method is a powerful tool to learn detail about the microscale behavior of the flow, but there is still a long distance from the experimental measurements and the real situations. In this project, the scale of microchannel range from dozens of nanometers to 100 nanometers, nanoparticle diameter from a few nanometers to dozens of nanometers. The problem is a mesoscopic one. By using coarse graining method, this project will develop a hybrid method coupling the Molecular Dynamics (MD) method and the Dissipative Particle Dynamics (DPD) method together, to achieve a multiscale simulation of the transportation, deposition and adsorption of nanoparticles in a microchannel. The experiences of this project may make some contribution to further research of macroscopic problems (at scale of micrometers).

随着纳米科技的发展，微通道中纳米颗粒的输运、沉积和吸附问题已开始引起广泛的关注, 其应用遍布于能源、环境、健康和高新技术领域之中。 当微通道尺度小到一定程度时, 流动特征尺度与气体分子自由程数量级靠近（对于理想气体大约为70纳米）,或液体受限空间接近分子尺度（对于水大约5纳米），表面积与体积之比很大,界面效应、分子之间的相互作用等微观性质已对整体流动性质产生不可忽略的影响。纳米颗粒的输运和动力学特性也与大尺度的颗粒有很大的不同。分子动力学模拟是研究流动微观性质的有力工具，但是距离实际问题和实验结果的尺度还有很大的距离。 本项目关注的微通道尺度从几十纳米到一百纳米，纳米颗粒直径从几纳米到几十纳米，属于介观尺度的问题。本项目将通过粗粒化方法，较好地实现分子动力学模拟与介观DPD方法的衔接，实现对微通道中纳米颗粒的输运、沉积和吸附的多尺度模拟，并为进一步与宏观问题（尺度在微米量级）的衔接提供借鉴

本项目通过粗粒化方法，实现分子动力学模拟与介观DPD 方法的衔接， 以较高效率实现对微通道中纳米颗粒的输运、沉积和吸附的多尺度模拟，正确反映微观效应对整体流动的影响。探索在微观模拟基础上粗粒化、 并与微观信息有较直接联系的介观模拟方法，并为进一步与宏观问题（通道尺度达到几十微米）的衔接提供借鉴。.通过对液氩和LJ流体平面Poiseuille 流的模拟，将介观耗散粒子动力学模拟结果与中子散射实验的结果及微观分子动力学模拟联系起来，得到了比较完整的模拟结果，为检验各种尺度的数值模拟方法提供了较为详细可靠的依据。系统地讨论了微观和介观模拟方法中各种参数和物理性质模拟的影响，给今后工作打下了较好的基础。与此同时，通过由宏观变量确定耗散粒子动力学作用力参数的方法将介观模拟方法与宏观现象相联系，研究了纳米颗粒的悬浮、沉降等规律。

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