纳米通道内气泡核化的分子动力学模拟

Molecular Dynamics Simulation of Bubble Nucleation in Nanochannel

为了探讨壁面浸润性与流体初始密度对气泡核化位置以及纳米气泡在凹槽内生长核化影响规律,采用分子动力学方法研究纳米结构微通道内液体氩的沸腾核化过程。通过改变固液势能的相互作用参数来调整壁面浸润性。结果表明:纳米凹槽壁面浸润性对气泡核化过程具有重要的影响。一方面,当固体表面的浸润性较弱时,凹槽内流体受排斥力的作用,原子排布比较稀疏,原子碰撞频率增大,局部活化能聚集,从而导致气泡在纳米凹槽内形成;另一方面,当壁面浸润性较强时,气泡会在微通道中央形成。此外,区别于均质浸润性纳米凹槽内气泡曲率半径及接触角保持不变的核化动力学行为,其在异质亲疏水匹配的纳米结构微通道内产生了显著的差异。当壁面浸润性维持不变,核化气泡的曲率半径随着流体初始密度增大而增大,与之相反,稳态接触角却随之减小。

In order to investigate the effect of wall wettability and initial fluid density on the nucleation and growth of nanobubbles in the grooves, molecular dynamics method are used to study the nucleation boiling process of liquid argon in microchannel. The wettabilities are changed by adjusting the parameters of the solid-liquid potential energy. The results show that the nano-groove wettability has an important influence on the bubble nucleation process. On the one hand, when the solid surface is a hydrophobic wall, the fluid in groove is affected by the repulsive force, thus the atomic density is sparse, the atomic collision frequency increases, and the local activation energy is concentrated, resulting in bubbles in the nano-groove. On the other hand, when the solid wall is a hydrophilic surface, the bubble is formed in the center of the microchannel. In addition, the bubble curvature radius and contact angle kept unchanged for homogeneous wettability microchannel, which are significantly different from the heterogeneous wettability microchannel with nanostructure. When the wall wettability remains unchanged, the radius of the bubble curvature increases as the initial density of the fluid increases. Conversely, the steady state contact angle decreases.