Kobayashi Kazuya U, Shinohara Ryoko, Kurita Rei
Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo 192-0397, Japan.
J Phys Condens Matter. 2021 May 3;33(21). doi: 10.1088/1361-648X/abf2fc.
Two-dimensional convection rolls are usually stable near the critical Rayleigh number in single component fluids. However, in binary mixtures, it has been reported that the roll patterns become unstable over time and that stagnant domains are transiently formed. The formation of transient stagnant domains (TSD) occurs in systems where one component is more viscous than the other. Meanwhile, the mechanism of the TSD formation has been unclear yet. Here, we use experiments using well-mixed silicone oils and colloidal suspensions to show that the formation of transient stagnant regions is chiefly related to the concentration dependence of the kinematic viscosity rather than spatially averaged properties. Furthermore, we find that the concentration dependence of density is also related to the formation of stagnant regions. The coupling between density, viscosity and concentration fluctuations may play an important role for thermal convection in multi-component mixtures.
在单组分流体中，二维对流卷在临界瑞利数附近通常是稳定的。然而，在二元混合物中，有报道称卷状模式会随时间变得不稳定，并且会短暂地形成停滞区域。瞬态停滞区域（TSD）的形成发生在一种组分比另一种组分粘性更大的系统中。同时，TSD形成的机制尚不清楚。在这里，我们使用充分混合的硅油和胶体悬浮液进行实验，以表明瞬态停滞区域的形成主要与运动粘度的浓度依赖性有关，而不是与空间平均性质有关。此外，我们发现密度的浓度依赖性也与停滞区域的形成有关。密度、粘度和浓度波动之间的耦合可能对多组分混合物中的热对流起重要作用。
