Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000 Rennes, France.
Soft Matter. 2019 Feb 13;15(7):1562-1570. doi: 10.1039/c8sm01855c.
The role of surface tension gradients in the apparent viscosity of liquid foams remains largely unexplained. In this article, we develop a toy-model based on a periodic array of 2D hexagonal bubbles, each bubble being separated from its neighbors by a liquid film of uniform thickness. The two interfaces of this thin liquid film are allowed to slide relatively to each other, thus shearing the liquid phase in between. We solve the dynamics under external shear of this minimal system and we show that the continuity of the surface tension around the whole bubble is the relevant condition to determine the bubble rotation rate and the energy dissipation. This result is expected to be robust in more complex situations and illustrates that thin film dynamics should be solved at the scale of the whole bubble interface when interface rheology matters.
表面张力梯度在液体泡沫表观黏度中的作用在很大程度上仍未得到解释。在本文中，我们基于二维六方泡的周期性排列开发了一个模型，每个泡被厚度均匀的液体膜与相邻泡隔开。允许这个薄液膜的两个界面相互滑动，从而剪切中间的液相。我们求解了这个最小系统在外剪切下的动力学，并表明整个泡的表面张力连续性是确定泡旋转速率和能量耗散的相关条件。这一结果在更复杂的情况下有望是稳健的，并说明当界面流变学起作用时，应在整个泡界面的尺度上求解薄膜动力学。
