Teshigawara Ryohei, Onuki Akira
Department of Physics, Kyoto University, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2010 Aug;82(2 Pt 1):021603. doi: 10.1103/PhysRevE.82.021603. Epub 2010 Aug 11.
We investigate the dynamics of spreading of a small liquid droplet in gas in a one-component simple fluid, where the temperature is inhomogeneous around 0.9T{c} and latent heat is released or generated at the interface upon evaporation or condensation (with T{c} being the critical temperature). In the scheme of the dynamic van der Waals theory, the hydrodynamic equations containing the gradient stress are solved in the axisymmetric geometry. We assume that the substrate has a finite thickness and its temperature obeys the thermal diffusion equation. A precursor film then spreads ahead of the bulk droplet itself in the complete wetting condition. Cooling the substrate enhances condensation of gas onto the advancing film, which mostly takes place near the film edge and can be the dominant mechanism of the film growth in a late stage. The generated latent heat produces a temperature peak or a hot spot in the gas region near the film edge. On the other hand, heating the substrate induces evaporation all over the interface. For weak heating, a steady-state circular thin film can be formed on the substrate. For stronger heating, evaporation dominates over condensation, leading to eventual disappearance of the liquid region.
我们研究了单组分简单流体中，在温度约为0.9Tc且蒸发或冷凝时界面释放或产生潜热（Tc为临界温度）的情况下，小液滴在气体中的扩散动力学。在动态范德瓦尔斯理论框架下，含梯度应力的流体动力学方程在轴对称几何结构中求解。我们假设基底具有有限厚度，其温度服从热扩散方程。在完全润湿条件下，前驱膜会在本体液滴之前铺展。冷却基底会增强气体在前进膜上的冷凝，这主要发生在膜边缘附近，可能是后期膜生长的主导机制。产生的潜热会在膜边缘附近的气体区域产生一个温度峰值或热点。另一方面，加热基底会使整个界面发生蒸发。对于弱加热，可在基底上形成稳态圆形薄膜。对于更强的加热，蒸发超过冷凝，导致液体区域最终消失。
