论文标题
不混溶的双层胶片的毛细管水平
Capillary Levelling of Immiscible Bilayer Films
论文作者
论文摘要
薄膜中的流量高度取决于边界条件。在这里，我们研究了由两种不混溶液体组成的薄双层膜的毛细管水平。具体而言，将阶梯的聚合物层放在另一个平坦的聚合物层上。台阶的曲率产生的拉普拉斯压力梯度在两层中诱导流动，从而消散了阶梯界面中存储的多余毛细管能量。研究了底层和顶层之间不同粘度比的影响。我们调用了低雷诺 - 噪声流体动力学的长波膨胀，以模拟两层偶联的粘性流而引起的能量耗散。在实验和模型之间发现了良好的一致性。对后者的分析进一步揭示了一个有趣的双重交叉，从Poiseuille流到插头流，最后到Couette流。交叉时间尺度取决于两种液体之间的粘度比，从而可以选择耗散机制，并通过改变该比率进行细微调节。
Flow in thin films is highly dependent on the boundary conditions. Here, we study the capillary levelling of thin bilayer films composed of two immiscible liquids. Specifically, a stepped polymer layer is placed atop another, flat polymer layer. The Laplace pressure gradient resulting from the curvature of the step induces flow in both layers, which dissipates the excess capillary energy stored in the stepped interface. The effect of different viscosity ratios between the bottom and top layers is investigated. We invoke a long-wave expansion of low-Reynolds-number hydrodynamics to model the energy dissipation due to the coupled viscous flows in the two layers. Good agreement is found between the experiments and the model. Analysis of the latter further reveals an interesting double crossover in time, from Poiseuille flow, to plug flow, and finally to Couette flow. The crossover time scales depend on the viscosity ratio between the two liquids, allowing for the dissipation mechanisms to be selected and finely tuned by varying this ratio.
